Gas carburizing method and gas carburizing apparatus

Abstract

To provide a gas carburizing apparatus and a gas carburizing method capable of keeping carburizing nonuniformity and / or sooting of a workpiece within an acceptable range.SOLUTION: A gas carburizing apparatus of the present invention comprises a carburizing chamber configured to heat a workpiece under atmospheric pressure or a pressure higher than atmospheric pressure, and a raw gas supply device configured to supply to the carburizing chamber a mixed gas of a carrier gas and a carburizing gas containing acetylene, wherein an average concentration of acetylene contained in an atmosphere in the carburizing chamber during carburizing treatment of the workpiece is set to 0.25 vol.% or less, and the same average concentration is set to 0.10 vol.% or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas carburizing method and a gas carburizing apparatus. [Background technology]

[0002] Conventionally, gas carburization of workpieces has been performed to harden the surface layer of metal workpieces. As a gas carburization method for workpieces using gas, one has been proposed in which workpieces placed in a heat treatment furnace under atmospheric pressure are heated while a carrier gas and a carburizing gas are supplied into the heat treatment furnace (see, for example, Patent Document 1). In this gas carburization method, nitrogen is used as the carrier gas and acetylene is used as the carburizing gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-166035 Summary of the Invention [Problem to be solved by the invention]

[0004] In the gas carburizing method of Patent Document 1, if the acetylene concentration in the mixed gas of carrier gas and carburizing gas is low, uneven carburizing of the workpiece occurs. On the other hand, if the acetylene concentration is high, a large amount of soot is generated in the furnace due to thermal decomposition. In other words, sooting occurs.

[0005] In view of the above circumstances, the present invention aims to provide a gas carburizing method and gas carburizing apparatus that can suppress uneven carburizing and / or sooting of a workpiece within an acceptable range. [Means for solving the problem]

[0006] The gas carburizing apparatus of the present invention comprises a carburizing chamber in which a workpiece is heated at atmospheric pressure or at a pressure higher than atmospheric pressure, and a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber, and is characterized in that the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.25% by volume or less.

[0007] The gas carburizing apparatus of the present invention comprises a carburizing chamber in which a workpiece is heated at atmospheric pressure or at a pressure higher than atmospheric pressure, and a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber, and is characterized in that the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.10% by volume or more.

[0008] The gas carburizing apparatus of the present invention comprises a carburizing chamber in which a workpiece is heated at atmospheric pressure or at a pressure higher than atmospheric pressure, and a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber, and is characterized in that the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.10% by volume or more and 0.25% by volume or less.

[0009] The gas carburizing method of the present invention is a gas carburizing method in which a mixed gas of a carrier gas and a carburizing gas is supplied to a workpiece to carburize the workpiece, wherein the carburizing gas contains acetylene, and the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to 0.25% by volume or less.

[0010] The gas carburizing method of the present invention is a gas carburizing method in which a mixed gas of a carrier gas and a carburizing gas is supplied to a workpiece to carburize the workpiece, wherein the carburizing gas contains acetylene, and the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to 0.10% by volume or more.

[0011] The gas carburizing method of the present invention is a gas carburizing method in which a mixed gas of a carrier gas and a carburizing gas is supplied to a workpiece to carburize the workpiece, wherein the carburizing gas contains acetylene, and the average concentration of acetylene in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to be 0.10% by volume or more and 0.25% by volume or less.

[0012] The gas carburizing apparatus of the present invention is characterized by comprising: a carburizing chamber in which a workpiece is heated at atmospheric pressure or at a pressure higher than atmospheric pressure; a raw material gas supply device that supplies a carrier gas and a carburizing gas containing acetylene to the carburizing chamber; an acetylene concentration meter that detects the acetylene concentration in the atmosphere in the carburizing chamber while the workpiece is being carburized; and a control device that feedback-controls the amount of acetylene supplied by the raw material gas supply device by referring to the concentration measured by the acetylene concentration meter so that the acetylene concentration in the atmosphere in the carburizing chamber becomes a target value.

[0013] In relation to the above gas carburizing apparatus, the raw material gas supply device may be characterized in that it adjusts the concentration of acetylene contained in the atmosphere in the carburizing chamber by adjusting the supply amount of a mixed gas of acetylene and a carrier gas or the mixing ratio of acetylene in the mixed gas of acetylene and a carrier gas.

[0014] The above-described gas carburizing apparatus may further comprise a measurement outlet path for drawing the atmosphere in the carburizing chamber from the carburizing chamber to the outside, and an air pump provided midway along the measurement outlet path, and the acetylene concentration measuring device may be disposed downstream of the air pump in the measurement outlet path.

[0015] The gas carburizing apparatus may be characterized in that the flow rate of the atmosphere discharged from the carburizing chamber by the gas supply pump is 10% or less of the total flow rate of gas supplied to the carburizing chamber by the raw material gas supply device.

[0016] In relation to the above gas carburizing apparatus, the control device may be characterized in that the average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is controlled to 0.25% by volume or less. [Effects of the Invention]

[0017] The gas carburizing apparatus and gas carburizing method of the present invention can provide the excellent effect of suppressing uneven carburizing and / or sooting of a workpiece within an acceptable range. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a view showing an outer region and an antechamber of a gas carburizing apparatus according to a first embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a diagram showing the front chamber and subsequent sections of the gas carburizing apparatus. [Figure 3] (A) and (B) are time charts of the carburizing process using the gas carburizing equipment. [Figure 4] 3(A) to 3(C) are block diagrams showing the internal configuration of a control device of the gas carburizing apparatus. [Figure 5] (A) and (B) are diagrams showing in chronological order the operation of the gas carburizing equipment and the transport of the workpiece carrier to the front chamber. [Figure 6] (A) and (B) are diagrams showing in chronological order the operation of the gas carburizing equipment, with the workpiece carrier being transported from the antechamber to the carburizing chamber. Note that (B) omits the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94, but the configuration is the same as (A). [Figure 7] (A) and (B) are diagrams showing in chronological order the operation of the gas carburizing equipment, with the subsequent workpiece carrier being transported from the antechamber to the carburizing chamber. Note that (B) omits the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94, but the configuration is the same as (A). [Figure 8](A) is a diagram showing the state when the gas carburizing equipment is operating and the first work carrier in the line of carburizing chambers has arrived at the carburizing section. (B) is a diagram showing the state when the gas carburizing equipment is operating and the first work carrier in the line of carburizing chambers has arrived at the diffusion section. Note that (B) omits the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94, but the configuration is the same as (A). [Figure 9] (A) is a diagram showing the state when the gas carburizing equipment is operating and the first work carrier in the line of carburizing chambers has arrived at the temperature-reducing section. (B) is a diagram showing the state when the gas carburizing equipment is operating and the first work carrier in the line of carburizing chambers has passed through the temperature-reducing section and arrived at the quenching chamber. Note that (B) omits the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94, but has the same configuration as (A). [Figure 10] (A) is a diagram showing the state in which the gas carburizing equipment is operating and performing the main quenching chamber purging process in the quenching chamber. (B) is a diagram showing the state in which the workpiece carrier has been carried into the quenching chamber. Note that in this diagram, the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94 are omitted, but the configuration is the same as in Figure 2. [Figure 11] (A) and (B) are diagrams showing in chronological order the operation of the gas carburizing equipment and the workpiece carrier undergoing quenching in the quenching chamber. Note that in these diagrams, the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94 are omitted, but the configuration is the same as in Figure 2. [Figure 12] This figure shows the gas carburizing equipment in operation, with the workpiece carrier in the quenching chamber undergoing oil removal and main purging. Note that the carburizing gas system 90, carrier gas system 92, and carburizing section supply system 94 are omitted in this figure, but the configuration is the same as in Figure 2. [Figure 13](A) and (B) are diagrams showing in chronological order the operation of the gas carburizing equipment, with a workpiece carrier being transported from the quenching chamber to the workpiece transport area, while the following workpiece carrier moves into the quenching chamber. Note that in these diagrams, the carburizing gas system 90, carrier gas system 92, carburizing section supply system 94, etc. are omitted, but the configuration is the same as in Figure 2. [Figure 14] FIG. 10 is a view showing the outer region and an antechamber of a gas carburizing apparatus according to a second embodiment of the present invention. [Figure 15] 3 is a time chart of the carburizing process of the gas carburizing apparatus. [Figure 16] (A) is a photograph of the experimental workpieces used in the experiment of Example 1. (B) is a time chart of the first carburizing treatment for 15 experimental workpieces housed on the first stand. (C) is a time chart of the second carburizing treatment for 15 experimental workpieces housed on the second stand. [Figure 17] (A) is a table showing the surface hardness results for each of the experimental workpieces (No. 1 to No. 15) on the first stand. (B) is a table showing the cross-sectional hardness results for the experimental workpieces No. 1, No. 7, No. 8, and No. 15 on the first stand. [Figure 18] This is a graph showing the acetylene concentration and hydrogen concentration in the experimental workpiece on the first stand and in the space surrounding it. [Figure 19] (A) is a table showing the surface hardness results for each of the experimental workpieces (No. 1 to No. 15) on the second stand. (B) is a table showing the cross-sectional hardness results for the experimental workpieces No. 1, No. 7, No. 8, and No. 15 on the second stand. [Figure 20] Photographs of (A) and (B) show stacked baskets containing experimental workpieces used in the experiment of Example 2. [Figure 21] (A) is a time chart showing the carburizing treatment conditions for multiple experimental workpieces housed in a first stacking cage, and (B) is a time chart showing the carburizing treatment conditions for multiple experimental workpieces housed in a second stacking cage. [Figure 22](A) is a photograph of three experimental workpieces placed in the first stacking cage after carburizing and quenching treatments. (B) is a photograph of three experimental workpieces placed in the second stacking cage after carburizing and quenching treatments. [Figure 23] These are high-magnification and low-magnification micrographs of the cross section of an experimental workpiece contained in the first stacking cage and the cross section of an experimental workpiece contained in the second stacking cage after carburizing and hardening treatments. [Figure 24] FIG. 10 is a diagram showing a gas carburizing apparatus according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] A first embodiment of the present invention will be described below with reference to the accompanying drawings. The accompanying drawings are an example of an embodiment of the present invention, and parts in the drawings that are given the same reference numerals represent the same objects. Furthermore, the shapes and dimensional ratios of the parts in each drawing are not necessarily accurate.

[0020] <Overall structure> 1 and 2, the gas carburizing apparatus in the first embodiment of the present invention carburizes a workpiece W in a continuous processing mode. The gas carburizing apparatus in this embodiment includes an outer region 1, a front chamber 2, a first connecting path 5A, a carburizing chamber 3, a second connecting path 5B, a quenching chamber 4, a workpiece unloading region 6, a front chamber transport device 70, a carburizing chamber transport device 71, a workpiece moving mechanism 72, a quenching chamber transport device 73, an unloading device 74, a front chamber negative pressure generating device 80, a quenching chamber negative pressure generating device 87, a front chamber purge gas supply device 84, a quenching chamber purge gas supply device 89, and a raw material gas supply device 9.

[0021] The outer region 1, front chamber 2, first connecting path 5A, carburizing chamber 3, second connecting path 5B, quenching chamber 4, and workpiece unloading region 6 are arranged in this order along the transport direction of the workpiece W. In other words, the workpiece W is transported in the order of the outer region 1, front chamber 2, first connecting path 5A, carburizing chamber 3, second connecting path 5B, quenching chamber 4, and workpiece unloading region 6.

[0022] As shown in Figures 1(A) and 2, the transport direction H1 of the work W from the external area 1 to the front chamber 2 and the transport direction H2 from the front chamber 2 to the work unloading area 6 are configured to be perpendicular to each other, but this is not limited to this.

[0023] Note that, as an example, the workpieces W are made of steel such as low carbon steel or low alloy steel (e.g., SCM415, SCM420, SCr415, SCr420), but are not limited thereto and may be made of other materials. Furthermore, the workpieces W may be transported arranged vertically and horizontally on a single-stage or multi-stage platform T (see FIG. 1(B)), or may be directly placed on a transport tray C and transported. Furthermore, as shown in FIG. 1(B), the platform T may be placed on the transport tray C and transported. In this embodiment, it is described that multiple workpieces W are accommodated on the platform T, and the platform T is placed on the transport tray C and transported. Hereinafter, for convenience of explanation, the platform T placed on the transport tray C will be referred to as a workpiece carrier Tc.

[0024] <External area> A front chamber transport device 70 is disposed in the external area 1. The front chamber transport device 70 transports the work carrier Tc into the front chamber 2 in the external area 1 via the front chamber entrance 20A. The front chamber transport device 70 may be any device capable of transporting the work carrier Tc in the transport direction H1, and may be configured, for example, by a conveyor device such as a snake chain transport or a self-propelled roller conveyor that is driven by a drive source and transports the work carrier Tc in the transport direction H1. However, the present invention is not limited to this and may be configured by a transport device of another type.

[0025] As shown in FIG. 1, an example of a conveying device including a snake chain includes a roller conveyor 70A that guides the work carrier Tc into the front chamber 2, a hook 70B that grips the engagement portion Cx of the work carrier Tc, a snake chain 70C that moves the hook 70B back and forth toward the front chamber 2, and a drive source 70D that drives the snake chain 70C via a sprocket. Note that, although a structure in which the engagement portion Cx is gripped by the hook 70B is exemplified here, because the conveying is in one direction, a conveying structure in which the tip of the snake chain 70C simply pushes the side of the work carrier Tc may also be used. However, the conveying device is not limited to this, and may be configured with a conveying device of another type.

[0026] The work carrier Tc is transported to a predetermined placement area of ​​the anterior chamber 2 by the anterior chamber transport device 70. When the work carrier Tc is placed in the placement area, the work carrier Tc is installed on the transport path 27 in a state where it can be guided in the transport direction H2. The transport path 27 may be provided with a guide rail (not shown) that guides the work carrier Tc (workpiece W) in the transport direction H2.

[0027] Furthermore, when the front chamber 2 is configured to be able to receive a plurality of work carriers Tc, the front chamber transport device 70 may transport the plurality of work carriers Tc to the front chamber 2 simultaneously or sequentially one by one.

[0028] <Front room> The anterior chamber 2 is formed of an airtight and / or pressure-resistant metal container. The anterior chamber 2 temporarily accommodates the carried-in work carrier Tc (workpiece W). A transport path 27 is provided in the anterior chamber 2 for transporting the work carrier Tc (workpiece W) in the transport direction H2. The workpiece carrier Tc is guided to the carburizing chamber 3 via the first connecting path 5A by guide rails provided on the transport path 27. The transport paths 27 are also provided in the first connecting path 5A, the carburizing chamber 3, the second connecting path 5B, the quenching chamber 4, and the workpiece unloading area 6.

[0029] 1(A), a front chamber entrance 20A serving as an opening is formed at the upstream end (boundary with the external area 1) in the conveying direction H1 of the front chamber 2. An openable front chamber entrance door 22 is disposed at this front chamber entrance 20A. The front chamber entrance door 22 closes the front chamber entrance 20A, thereby making the front chamber entrance 20A airtight (a state in which gas does not flow).

[0030] As shown in FIGS. 1A and 2, an opening, a front chamber outlet 20B, is formed at the downstream end of the front chamber 2 in the conveying direction H2 (at the boundary with the first connecting path 5A). A front chamber outlet door 24 that can be opened and closed is disposed at this front chamber outlet 20B. The front chamber outlet door 24 closes the front chamber outlet 20B, thereby making the front chamber outlet 20B airtight (a state in which gas does not flow). In FIG. 1A, the front chamber outlet door 24 is in an open state.

[0031] When the front room entrance door 22 and the front room exit door 24 are closed, the entire front room 2 becomes an airtight space.

[0032] <Front room entrance door> The front chamber entrance door 22 is a so-called vacuum door, and is opened and closed by a reciprocating drive mechanism 23 such as an air cylinder. Although not specifically shown, it is preferable to employ a pressing structure (for example, a parallel link structure or a slide mechanism) that presses the front chamber entrance door 22 against the front chamber entrance 20A when the front chamber entrance door 22 closes the front chamber entrance 20A by the reciprocating drive mechanism 23, thereby enhancing the airtight state.

[0033] <Exit door to the front room> The front chamber exit door 24 is a so-called vacuum door, and is opened and closed by a reciprocating drive mechanism 25 such as an air cylinder. Although not particularly shown, it is preferable to employ a pressing structure (for example, a parallel link structure or a slide mechanism) that presses the front chamber exit door 24 against the front chamber exit 20B when the front chamber exit door 24 closes the front chamber exit 20B by the reciprocating drive mechanism 25, thereby enhancing the airtight state.

[0034] <First Connection> As shown in FIG. 2, a tunnel-shaped first connecting path 5A is arranged between the front chamber 2 and the carburizing chamber 3. An opening, a front chamber outlet 20B, is formed on the front chamber 2 side of the first connecting path 5A (upstream side in the transport direction H2). The first connecting path 5A connects the front chamber 2 and the carburizing chamber 3 in an airtight manner so that gas does not enter from the external space. As already explained, a transport path 27 is also provided within the first connecting path 5A along the transport direction H2. The guide rails of the transport path 27 guide the workpiece carrier Tc transported via the first connecting path 5A to the carburizing chamber 3.

[0035] <Negative pressure generating device> The anterior chamber negative pressure generating device 80 creates a negative pressure state in the anterior chamber 2. As shown in FIG. 2, the anterior chamber negative pressure generating device 80 specifically includes a vacuum pump (negative pressure generating source) 81, a degassing flow path 82, and an on-off valve 83. The degassing flow path 82 connects the anterior chamber 2 to the vacuum pump 81. The vacuum pump 81 sucks (degasses) the gas in the anterior chamber 2, thereby creating a negative pressure state in the anterior chamber 2. Although not specifically shown, a filter or the like that adsorbs oil contained in the exhaust gas may be provided in the exhaust path beyond the vacuum pump 81. An electromagnetic on-off valve 83 is provided in the degassing flow path 82 and is opened during degassing.

[0036] <Pre-chamber purge gas supply device> A front chamber purge gas supply device 84 is connected to the front chamber 2. As shown in FIG. 2, the front chamber purge gas supply device 84 has a purge flow path 85, one end of which is connected to a purge gas source (here, the same nitrogen supply source 98 as the carrier gas is also used) and the other end of which is connected to the front chamber 2. An on-off valve 86 is disposed midway along the purge flow path 85. The on-off valve 86 is configured as an electromagnetic valve. The front chamber purge gas supply device 84 supplies a purge gas (here, nitrogen gas) to the front chamber 2, which has been degassed and placed in a negative pressure state by the front chamber negative pressure generating device 80, and this purge gas restores the front chamber 2 to normal pressure or a state higher than normal pressure (this is defined as a "pressure restored state").

[0037] <Carburizing chamber transport device> The carburizing chamber transfer device 71 transfers the workpiece carrier Tc to the carburizing chamber 3. As shown in FIG. 2, the carburizing chamber transfer device 71 is specifically composed of a pressing device 71A that can press the workpiece carrier Tc placed on the transfer path 27 of the front chamber 2 from the upstream side to the downstream side in the transfer direction H2. The pressing device 71A is composed of a reciprocating drive device that can reciprocate a piston rod 71B in the transfer direction H2, such as a hydraulic cylinder. When the piston rod 71B of this pressing device 71A presses the workpiece carrier Tc placed in the front chamber 2 in the transfer direction H2, the workpiece carrier Tc moves to the carburizing chamber 3 via the front chamber outlet 20B, the first connecting path 5A, and the carburizing chamber entrance 30A while being guided by the guide rails of the transfer path 27.

[0038] <Workpiece moving mechanism> The workpiece moving mechanism 72 moves the workpiece carrier Tc (workpiece W) inside the carburizing chamber 3A in the transfer direction H2. In this embodiment, the workpiece moving mechanism 72 moves the workpiece carriers Tc (workpiece W) lined up in a row along the transfer direction H2 in the carburizing chamber 3 in the transfer direction H2 each time the carburizing chamber transfer device 71 moves the workpiece carrier Tc (workpiece W) from the antechamber 2 to the carburizing chamber 3. The workpiece carriers Tc (workpieces W) lined up in a row along the transfer direction H2 in the carburizing chamber 3 are referred to as the preceding workpiece carrier row (preceding workpiece row) as appropriate. In this embodiment, the workpiece moving mechanism 72 is composed of the transfer path 27 extending in the transfer direction H2 inside the carburizing chamber 3A, and the carburizing chamber transfer device 71 (pressing device 71A).

[0039] On the transport path 27 inside the carburizing chamber 3A, multiple work carriers Tc (workpieces W) are lined up in a row along the transport direction H2. For this reason, when the carburizing chamber transport device 71 (pressing device 71A) moves the work carrier Tc (subsequent work carrier) from the anterior chamber 2 to the carburizing chamber 3, the subsequent work carrier Tc approaches the last work carrier Tc in the row of preceding work carriers (row of preceding works) arranged on the transport path 27. Then, the subsequent work carrier Tc pushes the entire row of preceding work carriers (row of preceding works) in the transport direction H2 through the last work carrier Tc. As a result, the entire row of preceding work carriers (row of preceding works) moves in the transport direction H2 together with the subsequent work carrier Tc.

[0040] Unlike the above, a carburizing chamber transfer device (first carburizing chamber transfer device) 71 may be used to move the subsequent work carrier Tc in the front chamber 2 in the transfer direction H2, and a carburizing chamber transfer device (second carburizing chamber transfer device) separate from the carburizing chamber transfer device 71 may be used to move the preceding work carrier row (preceding work row) in the transfer direction H2. The second carburizing chamber transfer device may be any device that can simultaneously move the entire preceding work carrier row (preceding work row) in the transfer direction H2, but it is envisioned that it may be configured, for example, by a device such as a roller conveyor (roller hearth type) that is driven by a drive source and transfers the work carrier Tc in the transfer direction H2. However, it is not limited to this and may be configured by other types of transfer devices.

[0041] <Carburizing chamber> The carburizing chamber 3 will be described with reference to FIG. 2. The carburizing chamber 3 is composed of an airtight, heat-resistant container or furnace. An opening, the carburizing chamber entrance 30A, is formed at the upstream end of the carburizing chamber 3 in the transport direction H2, i.e., at the boundary between the carburizing chamber 3 and the first connecting path 5A. A thermally insulated entrance door (carburizing chamber entrance door) 32A, which can be opened and closed by a reciprocating drive mechanism 33A, is located at the carburizing chamber entrance 30A. The thermally insulated entrance door 32A is made of a thermal insulating material and prevents heat from the carburizing chamber 3 from being transferred to the antechamber 2. The reciprocating drive mechanism 33A may be composed, for example, of a chain (not shown) connected to the thermally insulated entrance door 32A and a drive mechanism (not shown) that winds and unwinds the chain. The thermally insulated entrance door 32A may be moved up and down by an air cylinder.

[0042] An opening, carburizing chamber outlet 30B, is formed at the downstream end of the carburizing chamber 3 in the transport direction H2, i.e., at the boundary between the quenching chamber 4 and the second connecting path 5B. A heat-insulating exit door (carburizing chamber exit door) 32B that can be opened and closed by a reciprocating drive mechanism 33B is disposed at this carburizing chamber outlet 30B. The heat-insulating exit door 32B prevents heat from being transmitted from the carburizing chamber 3 to the quenching chamber 4. The reciprocating drive mechanism 33B is composed of, for example, a chain (not shown) connected to the heat-insulating exit door 32B and a drive mechanism (not shown: for example, a winch) that winds and unwinds the chain.

[0043] The carburizing chamber 3A is large enough to accommodate multiple workpiece carriers Tc lined up in a row along the transfer direction H2. A transfer path 27 for transferring the workpiece carriers Tc in the transfer direction H2 is provided in the carburizing chamber 3A. The multiple workpiece carriers Tc are lined up in a row on the transfer path 27 in the transfer direction H2. Rollers or the like may be arranged on the transfer path 27 to reduce transfer resistance.

[0044] If at least one preceding workpiece carrier Tc has already been carried into the carburizing chamber 3, when the subsequent workpiece carrier Tc is carried into the carburizing chamber 3 by the carburizing chamber transfer device 71, the preceding at least one workpiece carrier Tc is shifted downstream in the transfer direction H2 from its current position. Of the preceding at least one workpiece carrier Tc, the workpiece carrier Tc at the end (most upstream) of the line may be pushed and shifted in position by the subsequent workpiece carrier Tc being transferred from the anterior chamber 2 by the carburizing chamber transfer device (first carburizing chamber transfer device) 71, for example, or may be shifted in position by a second carburizing chamber transfer device separate from the carburizing chamber transfer device 71.

[0045] Next, the stopping positions of the multiple work carriers Tc lined up in a row inside the carburizing chamber 3A will be explained. The multiple work carriers Tc wait at preset stopping positions. Inside the carburizing chamber 3A, a first waiting position, a second waiting position, ..., an Nth waiting position are provided, in order from the upstream side of the transport direction H2, as waiting positions for N (16 in FIG. 1) work carriers Tc (group of workpieces W) to wait (temporarily stop). When a work carrier Tc temporarily stopped at the first waiting position is shifted downstream in the transport direction H2 from its current position by the first carburizing chamber transport device or the second carburizing chamber transport device, that work carrier Tc moves to the second waiting position and temporarily stops. In accordance with this, the other work carriers Tc also move to adjacent waiting areas downstream. This movement of the work carrier Tc is performed each time a subsequent work carrier Tc is carried in from the antechamber 2.

[0046] The carburizing chamber 3 also has a heating device 31 for heating the workpiece W in the carburizing chamber 3A, and a stirrer 34 provided in the carburizing chamber 3A.

[0047] The heating device 31 has multiple heaters 31A that heat the carburizing chamber 3A and a temperature sensor (not shown). The multiple heaters 31A are arranged at intervals in the transport direction H2. The multiple heaters 31A may be, for example, radiant tube heaters, but are not limited to these and may be other types of heaters.

[0048] It is preferable that a temperature sensor is provided in each of the sections (heating section S1, carburizing section S2, diffusion section S3, and cooling section S4) described later inside the carburizing chamber 3A.

[0049] Preferably, each of the plurality of heaters 31A is configured so that heating can be individually controlled by a control device 100, which will be described later, based on the measurement results of each temperature sensor.

[0050] The agitator 34 is provided on the ceiling surface of the carburizing chamber 3A and agitates the atmospheric gas inside the carburizing chamber 3A. It is preferable that an agitator 34 be provided in each of the sections (heating section S1, carburizing section S2, diffusion section S3, and temperature decreasing section S4) described below, but this is not limitative and an agitator 34 may be provided in only one specific section or multiple sections. The agitator 34 is, for example, formed from a centrifugal fan.

[0051] The carburizing chamber 3 is preferably provided with an exhaust path 36 and an on-off valve 36A for exhausting gas from the carburizing chamber 3A when purging the carburizing chamber 3A with a carrier gas. The exhaust path 36 and the on-off valve 36A are preferably provided at least in the temperature-rise section S1 (described later) of the carburizing chamber 3A, and in the diffusion section S3 and / or temperature-drop section S4 (described later). In particular, providing exhaust paths 36 in the temperature-rise section S1 and temperature-drop section S4 allows carrier gas supplied from the carburizing section S2 to flow into the most upstream temperature-rise section S1 and the most downstream temperature-drop section S4, thereby filling the entire carburizing chamber 3 with carrier gas. Furthermore, the first airflow formed by the flow of residual gas (carrier gas) from the carburizing section S2, via the temperature-rise section S1, into the exhaust path 36 in the temperature-rise section S1 suppresses the inflow of oxygen, water vapor, and the like from the carburizing chamber inlet 30A. Similarly, the second airflow formed by the flow of residual gas (carrier gas) flowing from the carburizing section S2 through the temperature-reducing section S4 and into the exhaust path 36 of the temperature-reducing section S4 suppresses the inflow of oxygen, water vapor, etc. from the carburizing chamber outlet 30B. This improves the carburizing characteristics of the workpiece W and suppresses carburizing variations and sooting. It is desirable that the carburizing chamber 3 be an airtight structure (pressure chamber) in order to maintain and control the internal pressure of the carburizing chamber 3A and reduce the amount of carrier gas used.

[0052] In addition, in this embodiment, an example has been given of purging the gas present in the carburizing chamber 3A with a carrier gas, but this is not limited to this, and the purge gas from the anterior chamber 2 may be introduced into the carburizing chamber 3A via the first connecting passage 5A to expel impurities from the carburizing chamber 3A.

[0053] Heat insulating material (not shown) is provided on the inner wall of the carburizing chamber 3A to maintain the temperature inside the carburizing chamber 3A. Furthermore, the carburizing chamber 3A is provided with an exhaust port (not shown) for discharging the atmospheric gas inside the carburizing chamber 3A to the outside of the furnace, and the carburizing chamber 3A is maintained at normal pressure (approximately atmospheric pressure: about 101 kPa) or a higher pressure than normal during carburizing.

[0054] In gas carburizing equipment, the carburizing process is carried out in the carburizing chamber 3A at normal pressure or a pressure higher than normal pressure. As a result, outside air (oxygen) is not drawn into the carburizing chamber 3A during the carburizing process, improving the carburizing quality. In this case, the carburizing process may be carried out at a pressure slightly higher than normal pressure (atmospheric pressure). A pressure slightly higher than normal pressure means, for example, a pressure in the range of above normal pressure but less than +10% of normal pressure. For example, a pressure of +5% or less of normal pressure is preferable, and a pressure of +1% or less of normal pressure is even more preferable.

[0055] <Multiple sections of the carburizing chamber> The carburizing chamber 3 is divided into multiple sections along the transport direction H2. The multiple sections include, for example, a temperature-raising section S1, a carburizing section S2, a diffusion section S3, and a temperature-reducing section S4. The temperature-raising section S1, the carburizing section S2, the diffusion section S3, and the temperature-reducing section S4 are arranged in this order from upstream to downstream in the transport direction H2.

[0056] The temperature-raising section S1 is the first section in the carburizing chamber 3A aligned in the transport direction H2, and is a section for performing a temperature-raising process to raise the temperature of the workpieces W accommodated in the workpiece carrier Tc to a predetermined carburizing temperature T1 (a temperature suitable for carburizing). For this reason, the temperature-raising section S1 is maintained at the carburizing temperature T1 by the heating device 31.

[0057] Then, the workpiece carrier Tc passes from the most upstream standby position in the temperature rise section S1 to the most downstream standby position over the temperature rise time t1, which includes the preset soaking time t5 of the workpiece W, and then moves to the next carburizing section S2. The temperature rise time t1 refers to the time during which the temperature rise process is performed on a specific workpiece W in the temperature rise section S1. In this embodiment, the workpiece carrier Tc moves intermittently in the transfer direction H2 due to the pressing force of the pressing device 71A, staying in the temperature rise section S1 for a total of the temperature rise time t1, and then moves to the next carburizing section S2. In FIG. 2, the temperature rise section S1 includes multiple standby positions (first standby position to fourth standby position), and the carburizing section S2 includes multiple standby positions (fifth standby position to eighth standby position). The workpiece carrier Tc passes through multiple standby positions (first standby position (most upstream standby position) to fourth standby position (most downstream standby position)) over the temperature rise time t1, and then reaches the most upstream standby position (fifth standby position) in the carburizing section S2.

[0058] As shown in the time chart of the workpiece W in FIG. 4, the workpiece W accommodated in the workpiece carrier Tc transported to the temperature rising section S1 remains in the temperature rising section S1 for a further soaking time t5 even after the temperature rises and reaches the carburizing temperature T1.

[0059] The carburizing section S2 is the next section following the temperature-raising section S1, and is a section in which a carburizing gas supply process is performed on the workpiece W whose temperature has been raised to the carburizing temperature T1 in the temperature-raising section S1. The carburizing gas supply process refers to the process of supplying a carrier gas and carburizing gas to the workpiece W. As shown in the time chart for the workpiece W in Figure 4, in the carburizing section S2, the workpiece W is maintained at the carburizing temperature T1 while a carrier gas and carburizing gas are supplied.

[0060] Then, the workpiece carrier Tc passes from the most upstream standby position to the most downstream standby position in the carburizing section S2 during a preset carburizing time t2 for the workpiece W, and then moves to the next diffusion section S3. The carburizing time t2 for the workpiece W refers to the time during which carrier gas and carburizing gas are supplied to a specific workpiece W in the carburizing section S2. In this embodiment, the workpiece carrier Tc moves intermittently in the transfer direction H2 due to the pressing force of the pressing device 71A, staying in the carburizing section S2 for a total of the carburizing time t2, and then moves to the next diffusion section S3. In FIG. 2, the carburizing section S2 includes the fifth standby position to the eighth standby position, and the diffusion section S3 includes the ninth standby position to the twelfth standby position, and it is sufficient for the workpiece carrier Tc to pass from the fifth standby position (the most upstream standby position) to the eighth standby position (the most downstream standby position) over the carburizing time t2, and then reach the ninth standby position in the diffusion section S3.

[0061] The carburizing gas supplied to the carburizing section S2 is preferably a gas containing acetylene (C2H2) (hereinafter referred to as acetylene-containing gas). When acetylene is adsorbed onto the workpiece W, it is decomposed into carbon and hydrogen according to the reaction (C2H2 → 2C + H2), and the carbon C is absorbed into the workpiece W. Furthermore, acetylene has a fast decomposition (carburization) rate. Therefore, by adjusting the acetylene concentration in the atmosphere during the carburizing process in the carburizing section S2, almost all of the acetylene supplied to the carburizing section S2 is adsorbed and decomposed by the workpiece W placed in the carburizing section S2, and it is possible to prevent excess acetylene from the carburizing section S2 from flowing into the adjacent heating section S1 and diffusion section S3. As a result, the gases supplied to the temperature rise section S1 and the diffusion section S3 are almost exclusively carrier gas and hydrogen (H2), which means that there is almost no possibility of unexpected carburization, decarburization, sooting, oxidation, etc. occurring in the temperature rise section S1 and the diffusion section S3.

[0062] To achieve the above control, in this embodiment, an acetylene concentration measuring sensor 1000 that measures the acetylene concentration is installed in the carburizing section S2 to monitor the acetylene concentration in the atmosphere of the carburizing section S2. An example of the acetylene concentration measuring sensor 1000 is an infrared absorption type. The measurement results from the acetylene concentration measuring sensor 1000 are fed back to a control device 100 (described later). Based on the measurement results, the control device 100 controls the opening and closing of an on-off valve 90B (see FIG. 2) of a carburizing gas system 90 (described later) to control the amount of acetylene supplied per unit time. As a result, the acetylene concentration in the atmosphere of the carburizing section S2 is adjusted. Note that if the acetylene concentration in the atmosphere of the carburizing section S2 measured by the acetylene concentration measuring sensor 1000 is outside a predetermined range, a warning means (not shown) may be configured to warn an external party of the abnormality.

[0063] Acetylene concentration measuring sensors (not shown) may also be provided in other sections such as the temperature rising section S1, the diffusion section S3, etc. If an acetylene concentration equal to or higher than a preset threshold is detected in another section, the control device 100 may control the opening and closing of an on-off valve 90B (see FIG. 2) of the carburizing gas system 90 (described later) based on the measurement result, thereby controlling the amount of acetylene supplied per unit time and thereby controlling the acetylene concentration, or may be configured to notify the outside of an abnormality using an alarm means (not shown).

[0064] The diffusion section S3 is the next section following the carburizing section S2, in which the carbon that has penetrated into the workpiece W is appropriately diffused to form a hardened layer with the desired carbon concentration and thickness (carburization depth) on the workpiece W. As shown in the time chart for the workpiece W in Figure 4, the diffusion section S3 is maintained at the carburizing temperature T1 by the heating device 31 with only carrier gas and hydrogen (H2) (hereinafter referred to as carrier gas, etc.) being supplied.

[0065] Then, the workpiece carrier Tc passes from the most upstream standby position in the diffusion section S3 to the most downstream standby position within the predetermined diffusion time t3 for the workpiece W, and moves to the next temperature-reducing section S4. This allows a hardened layer to be formed on the surface of the workpiece W. The diffusion time t3 refers to the time required to perform the diffusion process on a specific workpiece W within the diffusion section S3. In this embodiment, the workpiece carrier Tc moves intermittently in the transfer direction H2 due to the pressing force of the pressing device 71A, staying in the diffusion section S3 for a total of the diffusion time t3 before moving to the next temperature-reducing section S4. As described above, if the amount of carburizing gas supplied per unit time is controlled to adjust the acetylene concentration in the mixed gas supplied to the carburizing section S2, the gas supplied to the diffusion section S3 will not contain acetylene and can be mainly composed of the carrier gas (nitrogen) and hydrogen (H2), so no problems will arise.

[0066] 2, the diffusion section S3 includes a plurality of standby positions (ninth standby position to twelfth standby position), and the temperature decreasing section S4 includes a plurality of standby positions (thirteenth standby position to sixteenth standby position). The work carrier Tc passes through the plurality of standby positions (ninth standby position (most upstream standby position) to twelfth standby position (most downstream standby position)) over the diffusion time t3, and then reaches the most upstream standby position (thirteenth standby position) of the temperature decreasing section S4.

[0067] The temperature-reducing section S4 is the next section following the diffusion section S3, and is a section for controlling the heating device 12 to reduce the temperature of the workpiece W to a preset quenching holding temperature T2. In the temperature-reducing section S4, the heating device 31 maintains the quenching holding temperature T2 while a carrier gas or the like is supplied. The quenching holding temperature T2 is preferably in the range of 800°C to 880°C, and more preferably in the range of 830°C to 850°C.

[0068] Then, the workpiece carrier Tc passes from the most upstream standby position to the most downstream standby position in the temperature reduction section S4 in a preset temperature reduction time t4 for the workpiece W, and moves to the next quenching chamber 4 in a state where its temperature has been reduced to the quenching holding temperature T2. Note that the temperature reduction time t4 refers to the time during which the temperature of a specific workpiece W is reduced to the quenching holding temperature T2 in the temperature reduction section S4 and maintained at that temperature. In this embodiment, the workpiece carrier Tc only needs to stay in the temperature reduction section S4 for a total of the temperature reduction time t4 while moving intermittently in the conveying direction H2 due to the pressing force of the pressing device 71A, and then move to the next quenching chamber 4.

[0069] 2, the temperature decreasing section S4 includes a plurality of standby positions (a thirteenth standby position to a sixteenth standby position). The workpiece carrier Tc passes through the plurality of standby positions (the thirteenth standby position (the most upstream standby position) to the sixteenth standby position (the most downstream standby position)) over the temperature decreasing time t4 before reaching the next quenching chamber 4.

[0070] As shown in the time chart of the workpiece W in FIG. 4, the workpiece W accommodated in the workpiece carrier Tc transported to the temperature-reducing section S4 remains in the temperature-reducing section S4 for a further quenching retention time t6 even after the temperature is reduced to the quenching retention temperature T2.

[0071] As described above, by dividing a single transport path into multiple sections, the carburizing process can be carried out efficiently and in a short time. In this embodiment, the carburizing process refers to a process that includes at least a temperature increase process, a carburizing gas supply process, and a diffusion process. The carburizing process may also include a temperature decrease process. The carburizing chamber 3 functions as a continuous furnace, since it performs different processes on the moving workpiece in each section while controlling the heating.

[0072] Partition walls 37 may be provided at the boundaries of each section (heating section S1, carburizing section S2, diffusion section S3, and cooling section S4). The partition walls 37 extend downward from the upper wall of the carburizing chamber 3A at the boundaries of each section to a position where they do not interfere with the work carrier Tc (workpiece W). The position where the partition wall 37 does not interfere with the work carrier Tc (workpiece W) refers to a position before the passing area through which the work carrier Tc (workpiece W) passes during transportation.

[0073] The partition wall 37 forms an area surrounded by the partition wall 37 and the wall that forms the carburizing chamber 3. Therefore, for example, in the carburizing section S2, a mixed gas of acetylene and a carrier gas can be retained in that area, and acetylene is actively consumed in the carburizing section S2. As a result, the amount of residual acetylene in the carburizing section S2 is reduced, and the amount of acetylene flowing into the temperature-rise section S1 and the diffusion section S3 can be suppressed. In other words, the temperature-rise section S1, the diffusion section S3, and the temperature-fall section S4 are mainly filled with the carrier gas for the carburizing section S2 and hydrogen gas, which is a product of the carburizing reaction. This suppresses the carburizing reaction in these sections (S1, S3, S4). Furthermore, because the diffusion section S3 and the temperature-fall section S4 are set to different temperatures, the presence of the partition wall 37 reduces the mutual influence of the temperatures in the diffusion section S3 and the temperature-fall section S4.

[0074] Each workpiece carrier Tc lined up in a row in the carburizing chamber 3A moves to an adjacent downstream standby position in the transfer direction H2 at the same time each time a workpiece carrier Tc is carried in from the antechamber 2. Therefore, as shown in Figure 2, if the temperature rise section S1, carburizing section S2, diffusion section S3, and temperature fall section S4 each have four standby positions, the temperature rise time t1, carburizing time t2, diffusion time t3, and temperature fall time t4 will be the same. By changing the number of standby positions in each of the temperature rise section S1, carburizing section S2, diffusion section S3, and temperature fall section S4, the temperature rise time t1, carburizing time t2, diffusion time t3, and temperature fall time t4 can each be freely set. If the time from when the previous workpiece is transferred from the antechamber 2 to the carburizing chamber 3 by the carburizing chamber transfer device 71 until the next workpiece is transferred from the antechamber 2 to the carburizing chamber 3 is defined as reference time S, the number of standby positions within the temperature rise section S1 is defined as a first number N1, the number of standby positions within the carburizing section S2 is defined as a second number N2, the number of standby positions within the diffusion section S3 is defined as a third number N3, and the number of standby positions within the temperature drop section S4 is defined as a fourth number N4, then the first number N1 is expressed as the ratio of the temperature rise time t1 to the reference time S (N1 = t1 / S). The second number N2 is expressed as the ratio of the carburizing time t2 to the reference time S (N2 = t2 / S). The third number N3 is expressed as the ratio of the diffusion time t3 to the reference time S (N3 = t3 / S). The fourth number N4 is expressed as the ratio of the temperature drop time t4 to the reference time S (N4 = t4 / S). For example, if the time (reference time) from transporting the workpiece carrier Tc to the anterior chamber 2, through the negative pressure generation process in the anterior chamber 2, to completing the anterior chamber purging process is set to 15 minutes, the temperature rise time t1 is set to 30 minutes, the carburization time t2 is set to 90 minutes, the diffusion time t3 is set to 120 minutes, and the temperature drop time t4 is set to 30 minutes, then there will be two standby positions in the temperature rise section S1, six standby positions in the carburization section S2, eight standby positions in the diffusion section S3, and two standby positions in the temperature drop section S4. In this embodiment, it is preferable to satisfy N1≦N2. It is also preferable to satisfy N2≦N3+N4.

[0075] <Source gas supply device> A raw material gas supply device 9 is connected to the carburizing chamber 3, which supplies various gases to the carburizing chamber 3A. The raw material gas supply device 9 has a carburizing gas system 90 through which carburizing gas flows, a carrier gas system 92 through which carrier gas flows, and a carburizing section supply system 94 that supplies the gases flowing through the carburizing gas system 90 and the carrier gas system 92 to the carburizing section S2 inside the carburizing chamber 3A. The raw material gas supply device 9 also has a hydrocarbon supply source 96 connected to the carburizing gas system 90 and a nitrogen supply source 98 connected to the carrier gas system 92. In this embodiment, direct carburizing, in which the carbon contained in the carburizing gas directly penetrates the workpiece W, is performed under normal pressure, so the term "carburizing gas" is used instead of "enriched gas."

[0076] <Hydrocarbon Source> The hydrocarbon supply source 96 generates a hydrocarbon-containing gas containing a chain unsaturated hydrocarbon as the carburizing gas. In this embodiment, acetylene (C2H2) is preferred as the chain unsaturated hydrocarbon in the hydrocarbon-containing gas, considering the aforementioned fast decomposition (carburization) rate, high adsorption to steel, the fact that the triple bond makes it more reactive, and ease of availability. It is preferable to use acetylene with a purity of, for example, 95% by volume or higher, and more preferably, 98% by volume or higher. The hydrocarbon-containing gas may contain impurities other than the chain unsaturated hydrocarbon, but the amount of these impurities is preferably kept low. Therefore, for example, when the chain unsaturated hydrocarbon is acetylene, it is preferable that the hydrocarbon-containing gas is not generated using a solvent such as acetone or dimethylformamide (DMF) in the hydrocarbon supply source 96.

[0077] However, as the chain unsaturated hydrocarbon in the hydrocarbon-containing gas, other than acetylene, other chain unsaturated hydrocarbons having a triple bond such as propyne (CH3C≡CH) or 1-butyne (CH3CH2C≡CH) may be used, or other chain unsaturated hydrocarbons having a double bond such as ethylene (HC=CH2) or butadiene (CH2=CH-CH=CH2) may be used. Multiple types of chain unsaturated hydrocarbons may be mixed.

[0078] <Carburizing gas system> As shown in FIG. 2, the carburizing gas system 90 includes a supply pipe 90A connected to a hydrocarbon supply source 96, an on-off valve 90B attached to the supply pipe 90A, and a flow meter 90C. The supply pipe 90A is connected to the hydrocarbon supply source 96, through which carburizing gas flows. The on-off valve 90B is a solenoid valve attached to the supply pipe 90A. The on-off valve 90B opens and closes the flow path and adjusts the flow rate of the carburizing gas. The flow meter 90C is attached to the supply pipe 90A downstream of the on-off valve 90B and measures the flow rate of the carburizing gas flowing through the supply pipe 90A. The on-off valve 90B only opens and closes the flow path. Alternatively, a separate flow control valve (not shown) may be provided to adjust the flow rate of the carburizing gas, allowing manual adjustment of the carburizing gas flow rate while checking the readings on the flow meter 90C. The end of the supply pipe 90A is connected to a mixer 93 in the carburizing section supply system 94.

[0079] <Nitrogen source> The nitrogen supply source 98 generates a nitrogen-containing gas containing nitrogen (neutral gas or inert gas). This nitrogen-containing gas serves as a carrier gas. In this embodiment, the nitrogen supply source 98 includes a gas separation device 98A, which is a PSA-type nitrogen gas generator. The gas separation device 98A separates nitrogen from air using pressure swing adsorption (PSA) to generate the nitrogen-containing gas. Therefore, the nitrogen-containing gas contains oxygen as an impurity in addition to nitrogen. Note that the nitrogen-containing gas that serves as the carrier gas preferably has a nitrogen volume percentage of 99.00% or more. Furthermore, it is preferable that the oxygen volume percentage in the nitrogen-containing gas be 0.001% or more and 1.00% or less.

[0080] The nitrogen supply source 98 may supply the nitrogen-containing gas using a method other than the pressure swing adsorption method. For example, the nitrogen-containing gas may be generated and supplied using a nitrogen gas cylinder.

[0081] <Carrier gas system> The carrier gas system 92 includes a supply pipe 92A, an on-off valve 92B, and a flow meter 92C. A first end of the supply pipe 92A is connected to a nitrogen supply source 98, and a second end of the supply pipe 92A is connected to a mixer 93 of a carburizing section supply system 94.

[0082] Carrier gas or carrier gas to which a small amount of carburizing gas has been added in a gas mixer 91 flows through the supply pipe 92A. This carrier gas is guided to a mixer 93 in a carburizing section supply system 94. An on-off valve 92B is a solenoid valve that is provided midway through the supply pipe 92A. The on-off valve 92B opens and closes the flow path and adjusts the flow rate of the carrier gas. A flow meter 92C is provided on the supply pipe 92A downstream of the on-off valve 92B and measures the flow rate of the carrier gas flowing through the supply pipe 92A. Note that the on-off valve 92B only opens and closes the flow path, and a flow rate adjustment valve (not shown) that adjusts the flow rate of the carrier gas may be provided separately from the on-off valve 92B, and the flow rate of the carrier gas may be adjusted manually while checking the readings on the flow meter 92C.

[0083] When only carrier gas is supplied to the carburizing section S2, as in the carburizing chamber preparation process described below, the gas mixer 91 is stopped, the on-off valve 92B of the carrier gas line 92 is opened, and the on-off valve 90B of the carburizing gas line 90 is closed. The supply flow rate of the carrier gas is not particularly limited and may be set appropriately depending on the airtightness of the carburizing chamber, the volume of the carburizing chamber 3A, the surface area of ​​the workpiece W, the hardening depth required for the workpiece W, etc.

[0084] <Carburizing section supply system> The carburizing section supply system 94 has a mixer 93, and a first branch portion 941 and a second branch portion 942 that branch into two from the output side of the mixer 93. The input side of the mixer 93 is connected to a supply pipe 90A of the carburizing gas system 90 and a supply pipe 92A of the carrier gas system 92. The mixer 93 has the function of mixing the carburizing gas supplied from the upstream carburizing gas system 90 and the carrier gas supplied from the carrier gas system 92.

[0085] A first gas supply nozzle 941D is provided at the tip of the first branch portion 941, and a second gas supply nozzle 942D is provided at the tip of the second branch portion 942. The first gas supply nozzle 941D and the second gas supply nozzle 942D are provided above the carburizing chamber 3 in the carburizing section S2. The first gas supply nozzle 941D and the second gas supply nozzle 942D are provided with an interval in the transfer direction H2. The first gas supply nozzle 941D has a first supply port 941E that opens into the carburizing chamber 3A in the carburizing section S2. The second gas supply nozzle 942D has a second supply port 942E that opens into the carburizing chamber 3A in the carburizing section S2. From the first supply port 941E and the second supply port 942E, carburizing gas from the carburizing gas system 90 and carrier gas from the carrier gas system 92 are sprayed (or flowed) downward in the carburizing section S2.

[0086] Alternatively, the first gas supply nozzle 941D may be provided in the upper part of the carburizing chamber 3 in the carburizing section S2, and the second gas supply nozzle 942D may be provided in the lower part of the carburizing chamber 3. In this case, the carburizing gas from the carburizing gas system 90 and the carrier gas from the carrier gas system 92 are ejected (or flowed out) downward in the vertical direction from the first supply port 43a, and the carburizing gas from the carburizing gas system 90 and the carrier gas from the carrier gas system 92 are ejected upward in the vertical direction from the second supply port 44a.

[0087] Regardless of the arrangement pattern of the first gas supply nozzle 941D and the second gas supply nozzle 942D, it is preferable that the first gas supply nozzle 941D and the second gas supply nozzle 942D are arranged so that the carburizing gas is sprayed (or flowed out) evenly onto the workpiece W placed in the carburizing section S2 of the carburizing chamber 3.

[0088] The first branch section 941 and the second branch section 942 each include branch pipes 941A and 942A, on-off valves 941B and 942B, and flow meters 941C and 942C. These on-off valves 941B and 942B are solenoid valves that adjust the flow rates of gas flowing through the branch pipes 941A and 942A, thereby enabling adjustment of the ratio of the flow rates of gas flowing through the branch pipes 941A and 942A. The on-off valves 941B and 942B may be provided on only one of the branch pipes 941A and 942A. Alternatively, the on-off valves 941B and 942B may only open and close the flow path, and a flow rate adjustment valve (not shown) may be provided separately from the on-off valves 941B and 942B to adjust the flow rate of gas flowing through the branch pipes 941A and 942A, and the flow rate of gas flowing through the branch pipes 941A and 942A may be manually adjusted while checking the readings of the flow meters 941C and 942C.

[0089] In the above, the carburizing section supply system 94 has been exemplified as having a first branch portion 941 and a second branch portion 942 that branch into two from the output side of the mixer 93, but it is not limited to this, and a single flow path type that does not branch, or a type that branches into three or more paths, are also within the scope of the present invention. However, in any case, it is preferable that the gas supply nozzles in the carburizing section supply system 94 are provided above and / or below the carburizing section S2, and configured so that the carburizing gas and carrier gas are sprayed (or flowed out) downward and / or upward.

[0090] Although not shown here, in order to perform sulfurizing-carburizing and sulfuric-carbonitriding, the raw material gas supply device 9 may further include a hydrogen sulfide supply source and a hydrogen sulfide gas supply system for supplying hydrogen sulfide gas to the carburizing chamber 3A. The raw material gas supply device 9 may also additionally supply ammonia as a raw material gas.

[0091] <Application example of carrier gas supply system> 2, a gas mixer 91 may be provided upstream of an on-off valve 92B in a carrier gas system 92. This gas mixer 91 is provided upstream of the on-off valve 92B and a flow meter 92C, and serves to add a small amount of carburizing gas from a carburizing gas system 90 to the carrier gas (nitrogen gas) of a nitrogen supply source 98 as needed. For this reason, the carburizing gas system 90 is provided with a supply pipe 91A that branches off from a supply pipe 90A and is connected to the gas mixer 91. The flow rate (amount added) of the carburizing gas flowing through the supply pipe 91A is measured by a flow meter 91B, and the flow rate is adjusted by an on-off valve 91C.

[0092] A portion of the carrier gas to which a trace amount of carburizing gas has been added via gas mixer 91 flows through supply pipe 92A and into mixer 93, while the remainder flows through dedicated carrier gas pipe 91D, which branches off from supply pipe 92A. The downstream end of dedicated carrier gas pipe 91D is connected to temperature rise section S1. A flow meter 91E and an on-off valve 91F are provided in the dedicated carrier gas pipe 91D, and the amount of carrier gas to which a trace amount of carburizing gas has been added that is supplied to temperature rise section S1 is adjusted.

[0093] In this embodiment, oxygen is prevented from entering the temperature rise section S1, so in normal operation, oxygen does not have any adverse effects in the temperature rise section S1. However, if oxygen or water (steam) enters the temperature rise section S1 due to some event, it will preferentially adsorb to the surface of the workpiece W during temperature rise, hindering carburization.

[0094] Therefore, by opening the on-off valve 91F, carrier gas with a trace amount of carburizing gas added is supplied directly to the temperature-rising section S1. Specifically, water (water vapor) that enters the temperature-rising section S1 can be decomposed in the temperature-rising section S1 to generate hydrogen and oxygen, but the carrier gas with a trace amount of carburizing gas added is used to react acetylene with water to generate carbon monoxide and hydrogen, as shown in the following formula (1). This reduces the moisture concentration in the temperature-rising section S1. C2H2+2H2O→2CO+3H2 (1)

[0095] Furthermore, oxygen that enters the temperature rise section S1 is preferentially adsorbed onto the surface of the workpiece W, hindering carburization. However, as shown in the following equation (2), a small amount of acetylene added to the carrier gas reacts with oxygen to produce carbon monoxide and hydrogen. This reduces the oxygen concentration in the temperature rise section S1. C2H2+O2→2CO+H2 (2)

[0096] The amount of carburizing gas added directly to the temperature increasing section S1 is preferably sufficiently smaller than the volume of the carrier gas (nitrogen-containing gas), for example, 0.01% by volume or more and 3.0% by volume or less relative to the carrier gas.

[0097] It is also possible to increase the concentration of the carburizing gas supplied from the carburizing gas system 90 to the carburizing section S2 via the carburizing section supply system 94, thereby supplying excess acetylene to the carburizing section S2, causing a small amount of acetylene to leak into the temperature-raising section S1 via the carburizing section S2. This acetylene may be used to reduce the water and oxygen in the temperature-raising section S1.

[0098] <Second Connection> A tunnel-shaped second connecting passage 5B is arranged between the carburizing chamber 3 and the quenching chamber 4, connecting them. A carburizing chamber outlet 30B is formed as an opening on the carburizing chamber 3 side of the second connecting passage 5B (upstream side in the transport direction H2). The second connecting passage 5B connects the carburizing chamber 3 and the quenching chamber 4 in an airtight manner that prevents gas from entering from the outside space. A transport passage 27 is provided within the second connecting passage 5B for transporting the workpiece carrier Tc in the transport direction H2. The guide rails of the transport passage 27 guide the workpiece carrier Tc transported via the second connecting passage 5B to the quenching chamber 4.

[0099] <Quenching chamber transport device> The quenching chamber transfer device 73 transfers workpiece carriers Tc (hereinafter referred to as carburized workpiece carriers) that contain workpieces W that have been carburized and whose temperature has been lowered to the quenching holding temperature T2 in the temperature lowering section S4 to the quenching chamber 4. In this embodiment, the quenching chamber transfer device 73 transfers the carburized workpiece carriers Tc one by one to the quenching chamber 4. In this case, the quenching chamber transfer device 73 is configured to transfer the carburized workpiece carrier Tc that is located at the front (most upstream) of the line within the carburizing chamber 3A to the quenching chamber 4.

[0100] The quenching chamber transport device 73 may be any device that can transport the workpiece carrier Tc in the transport direction H2. For example, similar to the anterior chamber transport device 70 in Fig. 1, the quenching chamber transport device 73 may include a hook that grips the workpiece carrier Tc, a snake chain that is disposed in the oil tank 4B of the quenching chamber 4 and moves the hook back and forth between the temperature lowering section S4 and the quenching chamber 4, and a drive source that drives the snake chain via a sprocket.

[0101] Furthermore, when the quenching chamber 4 is configured to be able to receive a plurality of carburized work carriers Tc, the quenching chamber transport device 73 may transport a plurality of carburized work carriers Tc simultaneously within the carburizing chamber 3A or transport them one by one to the quenching chamber 4.

[0102] <Quenching chamber and oil tank> The quenching chamber 4 is formed of a pressure-resistant metal container. The quenching chamber 4 has an oil-throwing area 4A and an oil tank 4B. The oil-throwing area 4A and the oil tank 4B are aligned vertically, and the oil tank 4B is located below the oil-throwing area 4A. The workpiece carrier Tc transported via the second connecting path 5B is temporarily placed in the oil-throwing area 4A.

[0103] The quenching chamber 4 may be configured to include a heating device (not shown) and a temperature sensor (not shown) so that at least the oil-slinging region 4A is maintained at the quenching holding temperature T2.

[0104] Furthermore, an opening, a quenching chamber entrance 40A, is formed at the upstream end of the quenching chamber 4 in the transport direction H2, i.e., at the boundary between the quenching chamber 4 and the second connecting path 5B. A quenching chamber entrance door 42A that can be opened and closed by a reciprocating drive mechanism 49A is disposed at this quenching chamber entrance 40A. By closing the quenching chamber entrance 40A, the quenching chamber entrance door 42A makes the quenching chamber entrance 40A airtight (a state in which gas does not flow).

[0105] An opening, a quenching chamber outlet 40B, is formed at the downstream end of the quenching chamber 4 in the transfer direction H2. A quenching chamber outlet door 42B that can be opened and closed by a reciprocating drive mechanism 49B is disposed at this quenching chamber outlet 40B. The quenching chamber outlet door 42B closes the quenching chamber outlet 40B, thereby making the quenching chamber outlet 40B airtight (a state in which gas does not flow).

[0106] When the quenching chamber entrance door 42A and the quenching chamber exit door 42B are closed, the entire quenching chamber 4 becomes an airtight space.

[0107] The oil-slinging area 4A is provided with a transport path 27 for transporting the workpiece carrier Tc in the transport direction H2. Guide rails of the transport path 27 guide the workpiece carrier Tc to the workpiece unloading area 6 along the transport direction H2.

[0108] The oil tank 4B stores oil for quenching when hardening the workpiece W. As shown in Fig. 2, the oil tank 4B is equipped with a heater 46 for heating the oil, an agitator 47 for agitating the oil, and a heat exchanger 48 for cooling the oil. These devices allow the oil to be adjusted to a predetermined temperature.

[0109] An elevator device 40, which corresponds to a quenching moving device, is arranged in the quenching chamber 4. The elevator device 40 is installed between the oil-slinging area 4A and the oil tank 4B. The elevator device 40 raises and lowers the workpiece carrier Tc between the oil-slinging area 4A and the oil tank 4B.

[0110] As shown in FIG. 2, the lifting device 40 includes rails 43 extending in the arrangement direction (vertical direction) of the oil-slinging area 4A and the oil tank 4B, an elevator body 44 guided by the rails 43 in the arrangement direction, and a drive mechanism 45 that moves the elevator body 44 up and down. The drive mechanism 45 includes a lifting wire connected to the elevator body 44 and an electric drive mechanism that winds up the lifting wire. A conveying path 27 for conveying the work carrier Tc is provided within the elevator body 44. The lifting device 40 allows the elevator body 44 to move up and down (reciprocating) between the oil-slinging area 4A and the oil tank 4B. As the elevator body 44 moves up and down (reciprocating), a portion of the conveying path 27 within the elevator body 44 can also move up and down (reciprocating) between the oil-slinging area 4A and the oil tank 4B by the lifting device 40.

[0111] When the oil-slinging area 4A and the oil tank 4B are configured to be able to accommodate a plurality of work carriers Tc, the lifting device 40 can simultaneously lift and lower the plurality of work carriers Tc between the oil-slinging area 4A and the oil tank 4B.

[0112] <Quenching chamber negative pressure generating device> The quenching chamber negative pressure generating device 87 creates a negative pressure in the quenching chamber 4. Specifically, the quenching chamber negative pressure generating device 87 has a vacuum pump (negative pressure generating source) 87A, a degassing flow path 87B, and an on-off valve 87C. The degassing flow path 87B connects the quenching chamber 4 to the vacuum pump 87A. The vacuum pump 87A sucks (degasses) the gas inside the quenching chamber 4, thereby creating a negative pressure in the quenching chamber 4. Although not specifically shown, a filter or the like that adsorbs oil contained in the exhaust gas may be provided in the exhaust path beyond the vacuum pump 87A. An on-off valve 87C, which serves as an electromagnetic valve, is provided in the degassing flow path 87B and is opened during degassing.

[0113] The vacuum pump 87A may be omitted and the degassing passage 87B may be connected to the vacuum pump 81.

[0114] <Quenching chamber purge gas supply device> A quenching chamber purge gas supply device 89 is connected to the quenching chamber 4. The quenching chamber purge gas supply device 89 has a carrier gas system 89C through which carrier gas flows. The carrier gas system 89C has one end connected to a purge gas source (here, the same nitrogen supply source 98 as the carrier gas is also used) and the other end connected to the quenching chamber 4, a purge flow path 89A. An on-off valve 89B is arranged midway along the purge flow path 89A. The on-off valve 89B is configured as an electromagnetic valve. The quenching chamber purge gas supply device 89 supplies purge gas (here, nitrogen gas) to the quenching chamber 4, which has been degassed and placed in a negative pressure state by the quenching chamber negative pressure generating device 87, and this purge gas restores the quenching chamber 4 to normal pressure or a state higher than normal pressure (a restored pressure state).

[0115] <Work removal area> The workpiece unloading area 6 is an external area where the workpiece W that has been hardened in the quenching chamber 4 is unloaded. In the workpiece unloading area 6, for example, work is performed to ship the workpiece W that has been carburized and hardened.

[0116] <Export device> The carry-out device 74 carries out the work carriers Tc (hereinafter referred to as "hardened work carriers") that accommodate the workpieces W (hardened workpieces) that have been hardened in the quenching chamber 4, to the workpiece carry-out area 6. In this embodiment, the carry-out device 74 carries out the hardened workpiece carriers Tc to the workpiece carry-out area 6 one by one or multiple at the same time.

[0117] The carrying-out device 74 may be any device that can transport the workpiece carrier Tc in the transport direction H2. For example, similar to the anterior chamber transport device 70 in Fig. 1, the carrying-out device 74 may include a hook that grips the workpiece carrier Tc, a snake chain that is disposed in the workpiece carrying-out area 6 and moves the hook back and forth between the quenching chamber 4 and the workpiece carrying-out area 6, and a drive source that drives the snake chain via a sprocket.

[0118] <Control device> The control device 100 is a computer having a processor etc., and controls the entire gas carburizing device. As shown in Fig. 4(A), the control device 100 includes a CPU (Central Processing Unit) 101 that executes various programs, a memory 102 that temporarily stores information required by the CPU 101, an information storage medium 103 that stores programs and various data, and a communication interface 104 that communicates with various devices to be controlled.

[0119] <Individual functions of the control device> 4(B) shows individual control functions of the controlled devices realized by the control program of the control device 100. The control device 100 includes a front chamber transfer processing unit 110 that controls the transfer of the work carrier Tc (work W) by the front chamber transfer device 70, a front chamber entrance door opening / closing processing unit 111 that controls the reciprocating drive mechanism 23 to open and close the front chamber entrance door 22, a front chamber exit door opening / closing processing unit 112 that controls the reciprocating drive mechanism 25 to open and close the front chamber exit door 24, a front chamber degassing processing unit 113 that controls the vacuum pump 81 of the front chamber negative pressure generating device 80 to control the negative pressure state of the front chamber 2, a front chamber purge processing unit 114 that controls the front chamber purge gas supply device 84 to supply purge gas (here, nitrogen gas) to the front chamber 2, a heat insulating entrance door opening / closing unit 115 that controls the reciprocating drive mechanism 33A to open and close the heat insulating entrance door 32A; a heat insulating exit door opening / closing unit 116 that controls the reciprocating drive mechanism 33B to open and close the heat insulating exit door 32B; a carrier gas control unit 117 that controls the on-off valve 92B of the raw material gas supply device 9 to control the supply amount of carrier gas; a carburizing gas control unit 118 that controls the on-off valve 90B of the raw material gas supply device 9 to control the supply amount of carburizing gas; a carburizing chamber transport unit 71 that controls the movement of the work carrier Tc (work W) from the anterior chamber 2 to the carburizing chamber 3, or the movement of the work arranged in the carburizing chamber 3A; a carburizing chamber agitation processing unit 120 that controls the agitator 16 in the carburizing chamber 3; a carburizing chamber heating processing unit 121 that controls the heating device 31 in each section of the carburizing chamber 3A (heating section S1, carburizing section S2, diffusion section S3, and temperature decreasing section S4); a quenching chamber entrance door opening / closing processing unit 122 that controls the reciprocating drive mechanism 49A to open and close the quenching chamber entrance door 42A; a quenching chamber exit door opening / closing processing unit 123 that controls the reciprocating drive mechanism 49B to open and close the quenching chamber exit door 42B; and a quenching chamber transport device 73. a quenching chamber transport control unit 124 that controls the movement of the work carrier Tc (work W) to the quenching chamber 4 by controlling the above; a lifting processing unit 125 that controls the lifting device 40 that lifts and lowers the work carrier Tc (work W) between the oil throwing area 4A and the oil tank 4B; an oil tank heater processing unit 126 that controls the heater 46 of the oil tank 4B; an oil tank cooling processing unit 127 that controls the heat exchanger 48 of the oil tank 4B; an oil tank stirring processing unit 128 that controls the agitator 47 of the oil tank 4B; a quenching chamber degassing processing unit 129 that controls the vacuum pump 87A of the quenching chamber negative pressure generating device 87 to control the negative pressure state of the quenching chamber 4;It has a quenching chamber purge processing unit 130 that controls the quenching chamber purge gas supply device 89 to supply purge gas (here, nitrogen gas) to the quenching chamber 4, and a workpiece carry-out control unit 131 that controls the carry-out device 74 to control the movement of the workpiece carrier Tc (workpiece W) to the workpiece carry-out area 6.

[0120] In addition, when the work carrier Tc (work W) lined up in the carburizing chamber 3A is moved within the carburizing chamber 3A by the second carburizing chamber transport device (work moving mechanism 72), a second carburizing chamber transport control unit is separately provided which controls the second carburizing chamber transport device to control the movement within the carburizing chamber 3A of the work carrier Tc (work W) lined up in the carburizing chamber 3A.

[0121] <Controller integration functions> 4(C) shows the integrated control functions of the controlled devices implemented by the control program of the control device 100. The control device 100 has, as integrated control functions, an antechamber carry-in processing unit 150, antechamber purge management unit 152, a carburizing chamber preparation processing unit 154, a carburizing chamber carry-in processing unit 156, a carburizing processing unit 158, a quenching chamber main purge management unit 160, a quenching chamber carry-in processing unit 162, a quenching processing unit 164, an oil-slinging processing unit 166, a quenching chamber pre-purge management unit 168, a workpiece carry-out processing unit 170, an overall temperature management unit 171, and a fully automatic processing unit 172. These integrated control functions are linked with the individual control functions described above to achieve integrated control. Each integrated control function will be described below with reference to operational diagrams.

[0122] <Overall temperature control section> The overall temperature management unit 171 simultaneously operates the carburizing chamber agitation unit 120, the carburizing chamber heating unit 121, the oil bath heater unit 126, the oil bath cooling unit 127, and the oil bath agitation unit 128 to constantly maintain the target temperatures of the components, spaces, liquids, etc. in the gas carburizing apparatus. The overall temperature management unit 171 controls, for example, the heating device 31 to adjust the carburizing temperature T1 of the temperature increase section S1, the carburizing section S2, and the diffusion section S3 of the carburizing chamber 3 to 800°C or higher. For example, the carburizing temperature T1 is preferably controlled within a range of 880°C to 950°C, and more preferably 900°C to 930°C. The overall temperature management unit 171 is constantly running while the gas carburizing apparatus is in operation. The overall temperature management unit 171 controls, for example, the heating device 31 to adjust the temperature decrease section S4 to a preset quenching hold temperature T2. This quenching temperature T2 is preferably in the range of 800°C to 880°C, and more preferably in the range of 830°C to 850°C. The overall temperature control unit 171 may, for example, control a heating device (not shown) provided in the quenching chamber 4 to adjust the temperature inside the quenching chamber 4 to the same temperature as or close to the quenching temperature T2. The overall temperature control unit 171 may, for example, control a heating device (not shown) that heats the oil in the oil vat 4B to maintain the oil in the oil vat 4B at a predetermined quenching temperature T3. This quenching temperature T3 is preferably in the range of 50°C to 200°C. For example, the quenching temperature T3 is generally around 60°C for cold oil, around 120°C for semi-hot oil, and around 150°C for hot oil.

[0123] <Pre-chamber related processing> In the anterior chamber 2, an anterior chamber loading processor 150, an anterior chamber purge manager 152, and a carburizing chamber loading processor 156 are executed in this order. This series of processes is hereinafter defined as an anterior chamber-related process.

[0124] <Pre-chamber Loading Processing Section> 5(A) and (B), the front chamber carry-in processing section 150 opens the front chamber entrance door 22 and closes the front chamber exit door 24, and carries in the work carrier Tc (workpiece W) from the external area 1 to the front chamber 2. During the carrying-in process, outside air (oxygen, nitrogen, water) enters the front chamber 2.

[0125] In addition, the antechamber loading processing unit 150 mainly works in conjunction with the antechamber transport processing unit 110, the antechamber entrance door opening / closing processing unit 111, and the antechamber exit door opening / closing processing unit 112 to realize integrated control of processing related to the loading of the work carrier Tc (work W) into the antechamber 2.

[0126] <Front chamber purge control section> As shown in FIG. 6B, the antechamber purge management unit 152, which is executed after the antechamber loading unit 150, closes the antechamber entrance door 22 (not shown) and the antechamber exit door 24, opens the on-off valve 83 located in the degassing flow path 82 connected to the vacuum pump (negative pressure generating source) 81, and sucks out the internal gas of the antechamber 2 for 5 minutes to 30 minutes, preferably 10 minutes to 20 minutes, thereby creating a negative pressure state while discharging the invading air. The antechamber purge management unit 152 then opens the on-off valve 86 located in the purge flow path 85 connected to the purge gas source (nitrogen supply source 98) to supply purge gas (nitrogen gas) to the antechamber 2, which is in a negative pressure state, thereby restoring the antechamber 2 to normal pressure or a pressure higher than normal pressure. As a result, the antechamber 2 is filled with purge gas (nitrogen gas). Since the internal space of the antechamber 2 is at a preparation temperature T0, the workpiece W to be carried in is also maintained at the preparation temperature T0. In this embodiment, the preparation temperature T0 is the so-called room temperature (external ambient temperature), but the temperature may also be controlled by a heating device (not shown) such as a heater.

[0127] The front chamber purge management unit 152 mainly works in conjunction with the front chamber degassing unit 113 and the front chamber purge unit 114 to realize integrated control of the negative pressure state of the front chamber 2 and processing related to the purge gas.

[0128] <Carburizing chamber preparation processing section> As shown in FIG. 6(A), the carburizing chamber preparation unit 154 closes the insulated entrance door 32A and the insulated exit door 32B, and controls the on-off valve 92B of the carrier gas system 92 to supply carrier gas (nitrogen gas) to the carburizing chamber 3 through the first gas supply nozzle 941D and the second gas supply nozzle 942D, purging the carburizing chamber 3 with the carrier gas (carburizing chamber purging step). As a result, the carburizing chamber 3 is filled with purge gas (nitrogen gas). The amount of acetylene added to the carrier gas at this time is set to a lower concentration or zero than after transition to the carburizing unit described below. Note that the carburizing chamber preparation unit 154 is preferably executed simultaneously with or before the purging process of the anterior chamber purge management unit 152.

[0129] The carburizing chamber preparation processing unit 154 mainly works in conjunction with the carrier gas control unit 117 and the carburizing chamber heating unit 121 to realize integrated control of processing related to the purge gas in the carburizing chamber 3 .

[0130] <Carburizing chamber loading section> The carburizing chamber carry-in processing unit 156 is executed after the anterior chamber purge management unit 152 and the carburizing chamber preparation processing unit 154 are completed. The carburizing chamber carry-in processing unit 156 leaves the anterior chamber entrance door 22 closed, and opens the anterior chamber exit door 24 and the heat-insulated entrance door 32A as shown in FIG. 6(B). The carburizing chamber transfer device 71 (pressing device 71A) presses the workpiece carrier Tc from the anterior chamber 2 in the transfer direction H2 to move it into the carburizing chamber 3, and places the workpiece carrier Tc at the first standby position (the most upstream standby position) in the temperature rise section S1 of the carburizing chamber 3A. At this time, the nitrogen gas in the anterior chamber 2 and the nitrogen gas in the carburizing chamber 3 mix with each other. When the transfer of the workpiece carrier Tc is completed, the carburizing chamber transfer device 71 (pressing device 71A) returns to its initial state, and the anterior chamber exit door 24 and the heat-insulated entrance door 32A are closed, resulting in the state shown in FIG. 7(A). The workpiece W on the workpiece carrier Tc waiting at the first waiting position in the temperature rising section S1 is quickly heated to the carburizing temperature T1 in the temperature rising section S1 (see the time chart of the workpiece W in FIG. 3(A)).

[0131] During this time, the next workpiece carrier Tc (hereinafter referred to as the subsequent workpiece carrier) is subjected to pre-chamber-related processing in the pre-chamber 2. After the pre-chamber-related processing is completed, as shown in FIG. 7(B), the workpiece moving mechanism 72 presses the subsequent workpiece carrier Tc in the pre-chamber 2 in the transport direction H2 to move it to the carburizing chamber 3. The subsequent workpiece carrier Tc further pushes the preceding workpiece carrier Tc (hereinafter referred to as the preceding workpiece carrier) at the first standby position in the temperature-rise section S1. As a result, the subsequent workpiece carrier Tc is positioned at the first standby position in the temperature-rise section S1, and the preceding workpiece carrier Tc is shifted to the second standby position in the temperature-rise section S1. The preceding workpiece carrier Tc then undergoes temperature rise or soaking treatment at the second standby position in the temperature-rise section S1, and the subsequent workpiece carrier Tc is quickly heated to the carburizing temperature T1 at the first standby position in the temperature-rise section S1. By repeating these processes, the number of workpiece carriers Tc waiting in the temperature-rise section S1 increases.

[0132] The carburizing chamber loading processing unit 156 mainly works in conjunction with the anterior chamber entrance door opening / closing processing unit 111, the anterior chamber exit door opening / closing processing unit 112, the insulated entrance door opening / closing processing unit 115, the insulated exit door opening / closing processing unit 116, and the carburizing chamber transport control unit 119 to realize integrated control of the processes related to the transport of the workpiece carrier Tc (workpiece W) to the carburizing chamber 3.

[0133] <Carburizing Treatment Section>

[0134] When new pre-chamber-related processes are further repeated multiple times, the leading workpiece carrier Tc in the line inside the carburizing chamber 3A (hereinafter referred to as the leading workpiece carrier) moves to the fifth standby position, which is the most upstream standby position in the carburizing section S2, as shown in Figure 8(A) when the temperature rise time t1 has elapsed, calculated from the time when the leading workpiece carrier Tc is carried into the first standby position in the temperature rise section S1. As a result, the leading workpiece carrier Tc remains in the temperature rise section S1 for a total of the temperature rise time t1. When this leading workpiece carrier Tc enters the carburizing section S2, or slightly before that, the carburizing chamber preparation process unit 154 ends and the process transitions to the carburizing process unit 158.

[0135] The carburizing treatment unit 158 ​​controls the on-off valve 90B of the carburizing gas system 90 to supply a mixed gas of carrier gas (nitrogen gas) and carburizing gas (acetylene) to the carburizing chamber 3 through the first gas supply nozzle 941D and the second gas supply nozzle 942D. This performs carburizing gas supply treatment on the workpieces W accommodated in the leading workpiece carrier Tc that is positioned at the fifth standby position, which is the most upstream standby position of the carburizing section S2.

[0136] As with the carburizing chamber preparation treatment section 154, the carburizing chamber 3A is maintained at normal pressure while the carburizing treatment section 158 supplies the mixed gas. During the carburizing treatment, the flow rate per minute of the carrier gas is preferably controlled to 0.5 to 5.0 times the volume of the carburizing section S2. The flow rate of the carburizing gas is preferably controlled to 5 to 50 (L / min), taking into account the surface area of ​​the workpiece W.

[0137] Since the gas carburizing apparatus of this embodiment is a so-called continuous furnace, the supply of carburizing gas (acetylene) to the carburizing section S2 is constant during operation, as shown by the two-dot chain line in FIG. 3(B). Only the workpiece W passing through this carburizing section S2 is carburized. The supply of carburizing gas (acetylene) is continuous or intermittent. When the supply is intermittent, as shown in FIG. 3(B), the carburizing unit 158 ​​repeatedly opens the on-off valve 90B of the carburizing gas system 90 for a predetermined opening time to (e.g., 5 minutes) at a predetermined supply interval Io (e.g., 10 minutes). Note that the supply interval Io here refers to the interval between the timing at which the on-off valve 90B is opened, and does not refer to the interval between the closing of the on-off valve 90B after the opening time to and the next opening (the time the on-off valve 90B is closed). In this way, the carburizing unit 158 ​​can suppress the occurrence of excessive carburizing by supplying carburizing gas intermittently (in pulses) into the carburizing chamber 3A. At the same time, excessive supply of carbon to the workpiece W is suppressed, and the diffusion of carbon within the workpiece W is promoted, thereby reducing the occurrence of localized uneven carburizing. The occurrence of sooting can also be prevented.

[0138] When the carburizing gas is an acetylene-containing gas, the acetylene concentration in the atmosphere in the carburizing section S2 is adjusted. Specifically, through demonstration experiments by the inventors, the average acetylene concentration in the atmosphere in the carburizing section S2 is controlled to a range of 0.10% to 0.25% by volume by feedback control of the measurement results from the acetylene concentration measuring sensor 1000. The average concentration refers to the time average during the period when each workpiece W passes through the carburizing section S2. It is more preferable to constantly control the actual acetylene concentration in the atmosphere, rather than the average concentration, to a range of 0.10% to 0.25% by volume.

[0139] By controlling the average acetylene concentration to 0.25% by volume or less, almost all of the acetylene supplied to the carburizing section S2 is adsorbed and decomposed by the workpiece W placed in the carburizing section S2, reducing the amount of excess acetylene that flows into the adjacent heating section S1 and diffusion section S3. At the same time, sooting on the surface of the workpiece W due to excess acetylene can be suppressed.

[0140] On the other hand, by controlling the average acetylene concentration to 0.10% by volume or more, the variation in carburizing can be suppressed. Note that if the average acetylene concentration in the atmosphere in the carburizing section S2 is less than 0.10% by volume, acetylene shortages will occur in some locations within the carburizing section S2, which will likely result in variation in carburizing.

[0141] This "control within a range of 0.10 vol% or more to 0.25 vol% or less" will be described in detail. For example, from the viewpoint of suppressing sooting, the process of controlling the acetylene concentration to 0.25 vol% or less may be performed by controlling the "temporal average value" of the acetylene concentration during the carburizing treatment of the workpiece W to 0.25 vol% or less. In other words, the acetylene concentration may exceed 0.25 vol% for a very short period of time during the carburizing treatment. In other words, this includes a case where the target value for acetylene control is set so that the time average over a predetermined cycle (time) is 0.25 vol% or less. Similarly, this includes a case where the target value for acetylene concentration control is set to 0.25 vol% or less.

[0142] On the other hand, from the perspective of suppressing carburization variation, the process of controlling the acetylene concentration to 0.10 vol% or more means that the acetylene concentration should be controlled to 0.10 vol% or more for the amount of time required to reduce variation in the carburized layer formed on the workpiece W, and that the acetylene concentration may be controlled to less than 0.10 vol% for any excess time period. The process of controlling the acetylene concentration to 0.10 vol% or more may, for example, be controlled so that the "temporal average value" of the acetylene concentration during the carburization treatment of the workpiece W is 0.10 vol% or more. In other words, this includes the case where the target value for acetylene control is set so that the time average over a predetermined cycle (time) is 0.10 vol% or more. Similarly, this includes the case where the target value for acetylene concentration control is set to a value of 0.10 vol% or more.

[0143] Furthermore, when new pre-chamber-related processes are repeatedly performed multiple times during control by the carburizing unit 158, the leading workpiece carrier Tc moves to the ninth standby position, which is the most upstream standby position in the diffusion section S3, at the timing when carburizing time t2 has elapsed counting from the time when the leading workpiece carrier Tc is carried into the fifth standby position in the carburizing section S2, as shown in Figure 8(B). As a result, the leading workpiece carrier Tc stays in the carburizing section S2 for the total carburizing time t2.

[0144] When the leading workpiece carrier Tc moves to the ninth standby position, the diffusion process for the leading workpiece carrier Tc begins. The diffusion section S3 is maintained at the carburizing temperature T1 by the overall temperature control unit 171, which has already been described, while being filled with the carrier gas (a mixed gas of carrier gas and hydrogen gas) flowing out from the carburizing section S2.

[0145] Furthermore, when new pre-chamber-related processes are repeatedly performed multiple times during control by the carburizing treatment unit 158, the leading workpiece carrier Tc moves to the thirteenth standby position, which is the most upstream standby position in the temperature decreasing section S4, at the timing when the diffusion time t3 has elapsed counting from the time when the leading workpiece carrier Tc is carried into the ninth standby position, as shown in Figure 9(A). As a result, the leading workpiece carrier Tc stays in the diffusion section S3 for a total of the diffusion time t3.

[0146] Then, during the time period when the leading workpiece carrier Tc is in the diffusion section S3, the carbon that has penetrated into the workpiece W in the carburizing section S2 diffuses appropriately, forming a hardened layer of the desired thickness (carburization depth). Then, in the temperature-reducing section S4, the temperature-reducing process for the leading workpiece carrier Tc begins.

[0147] The temperature decreasing section S4 is maintained at a preset quenching holding temperature T2 by the overall temperature management unit 171 already described.

[0148] Furthermore, when new pre-chamber related processes are repeatedly performed multiple times during control by the carburizing processing unit 158, as shown in Fig. 9(B), at the timing when the temperature drop time t4 has elapsed from the time when the leading workpiece carrier Tc is carried into the thirteenth standby position or around that timing, the "quenching chamber related processes" described in detail below are executed, and the leading workpiece carrier Tc moves from the temperature drop section S4 to the quenching chamber 4. This means that the leading workpiece carrier Tc has stayed in the temperature drop section S4 for the temperature drop time t4 in total.

[0149] Thereafter, new pre-chamber related processing and quenching chamber related processing are repeatedly performed, and the workpieces W housed in each workpiece carrier Tc lined up in the carburizing chamber 3A are processed in the same way as the workpiece W housed in the leading workpiece carrier Tc.

[0150] The carburizing unit 158 ​​cooperates with the carrier gas control unit 117 and the carburizing gas control unit 118 to realize integrated control of the carburizing process.

[0151] <Quenching chamber related processing> Next, the above-mentioned quenching chamber-related processing will be described in detail. In the quenching chamber 4, the quenching chamber main purge management unit 160, the quenching chamber carry-in processing unit 162, the quenching processing unit 164, the oil draining processing unit 166, the quenching chamber pre-purge management unit 168, and the workpiece carry-out processing unit 170 are executed in this order. This series of processing is hereinafter defined as the quenching chamber-related processing. One cycle time of this quenching chamber-related processing is the same as one cycle time of the pre-chamber-related processing.

[0152] <Quenching Room Main Purge Control Department> After the workpiece W is removed from the quenching chamber 4 by the workpiece removal processing unit 170 (described later in FIG. 13), the quenching chamber main purge management unit 160, which is executed before the quenching chamber loading processing unit 162, closes the quenching chamber entrance door 42A and the quenching chamber exit door 42B as shown in FIG. 10(A) and opens the on-off valve 87C located in the degassing flow path 87B connected to the vacuum pump (negative pressure generating source) 87A, thereby discharging the air (oxygen) that has entered the quenching chamber 4 and creating a negative pressure. The on-off valve 89B of the carrier gas system 89C is then opened. This supplies purge gas (nitrogen gas) to the quenching chamber 4 through the purge flow path 89A connected to the purge gas source (nitrogen supply source 98). The quenching chamber 4 is purged with the carrier gas, and the pressure in the quenching chamber 4 is restored to normal pressure or a higher pressure than normal pressure (quenching chamber main purge process). As a result, the quenching chamber 4 is filled with purge gas (nitrogen gas). This is called the main quenching chamber purge process. In this state, the system waits for the timing to execute the next "quenching chamber loading process section."

[0153] The quenching chamber main purge management unit 160 mainly works in conjunction with the quenching chamber entrance door opening / closing processing unit 122, the quenching chamber exit door opening / closing processing unit 123, the quenching chamber degassing processing unit 129, and the quenching chamber purge processing unit 130 to realize integrated control of the negative pressure state of the quenching chamber 4 and processing related to the purge gas.

[0154] <Hardening chamber loading section> The quenching chamber loading process unit 162, which is executed following the quenching chamber main purge management unit 160, opens the insulation exit door 32B and the quenching chamber entrance door 42A and closes the quenching chamber exit door 42B, as shown in FIG. 10(B), and moves the workpiece carrier Tc from the carburizing chamber 3 to the oil-slinging area 4A of the quenching chamber 4 using the quenching chamber transfer device 73. At this time, since both the temperature-reducing section S4 and the quenching chamber 4 are filled with nitrogen gas (carrier gas), the nitrogen gases in both spaces mix with each other. At this time, the carrier gas in the temperature-reducing section S4 contains almost no acetylene, ensuring safety. Once the workpiece carrier Tc has been moved to the quenching chamber 4, the insulation exit door 32B and the quenching chamber entrance door 42A are closed, as shown in FIG. 11(A). It is preferable that the quenching chamber loading process unit 162 be executed each time a pre-chamber-related process is performed.

[0155] The quenching chamber loading processing unit 162 mainly works in conjunction with the insulation exit door opening / closing processing unit 116, the quenching chamber entrance door opening / closing processing unit 122, the quenching chamber exit door opening / closing processing unit 123, and the quenching chamber transport control unit 124 to realize integrated control of the movement processing of the work carrier Tc (work W) to the quenching chamber 4.

[0156] <Quenching processing section> The quenching process section 164, which is executed following the quenching chamber carry-in process section 162, lowers the workpiece carrier Tc (workpiece W) temporarily placed in the oil-slinging area 4A and immerses it in oil in the oil tank 4B to rapidly cool it (quenching process), as shown in Fig. 11(B). At this time, the oil vaporizes and becomes oil smoke, which fills the quenching chamber 4. The workpiece carrier Tc (workpiece W) is immersed in the oil tank 4B for the oil quenching time.

[0157] The quenching processing unit 164 mainly works in conjunction with the lifting and lowering processing unit 125 to realize integrated control of the quenching processing.

[0158] <Oil cutting processing section> The oil-draining processing section 166, which is executed following the quenching processing section 164, performs oil-draining by lifting the work carrier Tc (workpiece W) from the oil tank 4B to the oil-draining area 4A and leaving the work carrier Tc (workpiece W) in the oil-draining area 4A for a while, as shown in Figure 12.

[0159] The oil-cutting processing unit 166 mainly works in conjunction with the lifting / lowering processing unit 125 to realize integrated control.

[0160] <Quenching room pre-purge management department> The quenching chamber pre-purge management unit 168, which is executed following the quenching processing unit 164 or oil-slinging processing unit 166, maintains the quenching chamber entrance door 42A and quenching chamber exit door 42B, which are already closed, in a closed state, as shown in FIG. 12. The gas in the quenching chamber 4 during quenching processing is sucked out by a vacuum pump (negative pressure source) 87A, creating a negative pressure while discharging the oil (oil smoke) vaporized in the nitrogen gas together with the nitrogen gas. Then, purge gas (nitrogen gas) is supplied to the quenching chamber 4, restoring the quenching chamber 4 to atmospheric pressure or a pressure higher than atmospheric pressure. This is called quenching chamber pre-purge management. As a result, the quenching chamber 4, where the workpiece carrier Tc (workpiece W) waits after the quenching process is completed, is once again filled with only purge gas (nitrogen gas). In this embodiment, the purging process for exhausting oily smoke from the quenching chamber 4 is referred to as "pre-purge," and the process of purging oxygen, hydrogen, etc. from the quenching chamber 4 with nitrogen gas before the workpiece W is transported into the quenching chamber 4 is referred to as "main purge."

[0161] The quenching chamber pre-purge management unit 168 mainly works in conjunction with the quenching chamber entrance door opening / closing processing unit 122, the quenching chamber exit door opening / closing processing unit 123, the quenching chamber degassing processing unit 129, and the quenching chamber purge processing unit 130 to realize integrated control of the negative pressure state of the quenching chamber 4 and processing related to the purge gas.

[0162] <Work removal processing section> The workpiece carrying-out processing unit 170, which is executed following the quenching chamber pre-purge management unit 168, closes the quenching chamber entrance door 42A and opens the quenching chamber exit door 42B, and carries out the workpiece carrier Tc from the quenching chamber 4 to the workpiece carrying-out area 6 by the carrying-out device 74, as shown in FIG. 13(A). After the workpiece carrier Tc has been carried out to the workpiece carrying-out area 6, the workpiece carrying-out processing unit 170 closes the quenching chamber exit door 42B and starts the next new quenching chamber-related process (quenching chamber main purge management unit 160), as shown in FIG. 13(B). It is preferable that the workpiece carrying-out processing unit 170 perform the above-mentioned processes each time a pre-chamber-related process is executed.

[0163] The workpiece carrying-out processing unit 170 mainly works in conjunction with the quenching chamber entrance door opening / closing processing unit 122, the quenching chamber exit door opening / closing processing unit 123, and the workpiece carrying-out control unit 131 to realize integrated control of the carrying-out processing of the workpiece carrier Tc (workpiece W). After the workpiece carrying-out processing unit is completed, the quenching chamber main purge management unit 160 promptly performs main purging of the quenching chamber 4 as shown in Fig. 10(A) to prepare for the carrying-in of the next workpiece W.

[0164] (fully automatic processing unit) The fully automatic processing unit 172 realizes automatic continuous operation by continuously executing the integrated management functions described above. Specifically, while executing the overall temperature management unit 171, it executes the carburizing chamber preparation processing unit 154 only at the start of operation, and then transitions to the quenching processing unit 164 for continuous operation. At the same time, it automatically repeats (loops) the pre-chamber-related processing (pre-chamber carry-in processing unit 150, pre-chamber purge management unit 152, carburizing chamber carry-in processing unit 156) and the quenching chamber-related processing (quenching chamber main purge management unit 160, quenching chamber carry-in processing unit 162, quenching processing unit 164, oil-slinging processing unit 166, quenching chamber pre-purge management unit 168, workpiece carry-out processing unit 170). This makes it possible to perform carburizing and quenching processes on the lined-up workpiece carriers Tc (workpieces W) sequentially, starting from the front, while intermittently moving the workpiece carriers Tc (workpieces W) in the transport directions H1 and H2.

[0165] Next, a batch processing type gas carburizing apparatus according to a second embodiment of the present invention will be described with reference to Figure 14. Note that duplicated explanations of components and processing steps similar to those of the continuous processing type gas carburizing apparatus according to the first embodiment will be omitted, and the explanation will focus on the differences.

[0166] (Overall composition) 14, the gas carburizing apparatus includes a front chamber 2060, an oil tank 2070 provided below the front chamber 2060, and a carburizing chamber 2010 located adjacent to the front chamber 2060. The carry-in route Hin for the workpiece W is the outer region, front chamber 2060, and carburizing chamber 2010 in that order. The carry-out route Hout for the workpiece W is the carburizing chamber 2010, front chamber 2060, oil tank 2070, front chamber 2060, and outer region in that order.

[0167] An opening, a front room entrance / exit 2060a, is formed in the front room 2060 on the near side of the carry-in route Hin, and an openable and closable front room entrance / exit door 2050 is disposed in the front room entrance / exit 2060a.

[0168] A connecting path 2065 is disposed between the front chamber 2060 and the carburizing chamber 2010. An opening, a second front chamber entrance / exit 2060b, is formed on the front chamber 2060 side of the connecting path 2065, and an openable / closable second front chamber entrance / exit door 2066 is disposed at the front chamber second entrance / exit 2060b. A carburizing chamber entrance / exit 2010x is formed at the boundary between the carburizing chamber 2010 and the connecting path 2065, and an openable / closable heat-insulating door 2084 is disposed at this carburizing chamber entrance / exit 2010x.

[0169] An elevator device 2090, which corresponds to a quenching moving device, is disposed in the front chamber 2060 and the oil tank 2070. The elevator device 2090 can raise and lower the workpiece W and the transport tray C between the front chamber 2060 and the oil tank 2070.

[0170] (external area) A front chamber transport device 2080 is disposed in the external area. The front chamber transport device 2080 has a roller conveyor 2080a that guides a transport tray C on which the workpiece W is placed, a hook 2080b that grips the engaging portion Cx of the transport tray C, a snake chain 2080c that moves the hook 2080b back and forth toward the front chamber 2060, and a drive source 2080d that drives the snake chain 2080c via a sprocket. This front chamber transport device 2080 can transport a transport tray C disposed in the external area into the front chamber 2060, and transport a transport tray C disposed in the front chamber 2060 out to the external area.

[0171] (Front room entrance door) The front chamber entrance door 2050 is a so-called vacuum door, and is opened and closed by an air cylinder 2052 which serves as a reciprocating drive source.

[0172] (Second entrance door to the front room) The second front chamber entrance door 2066 is a so-called vacuum door, and is opened and closed by an air cylinder 2067 which serves as a reciprocating drive source.

[0173] (front room) A guide rail 2064 is disposed in the anterior chamber 2060 to guide the transport tray C along the carry-in path Hin or the carry-out path Hout. A vacuum pump (negative pressure generating source) 2062b is connected to the anterior chamber 2060 via a degassing flow path 2062a. An on-off valve 2062c, which is an electromagnetic valve, is provided in the degassing flow path 2062a and is opened during degassing.

[0174] (Insulated door) A heat-insulating door 2084 installed at the carburizing chamber entrance 2010x is made of a heat-insulating material, and is controlled to open and close by a chain 2086a and a drive mechanism 2086b (for example, a winch) which serve as a reciprocating drive source.

[0175] (Purge gas supply device) A purge gas supply device 2063 is connected to the front chamber 2060. The purge gas supply device 2063 includes a purge flow path 2063a having one end connected to the front chamber 2060, a purge gas source (here, the nitrogen supply source 2026, which is also used as the carrier gas) connected to the other end of the purge flow path 2063a, and an on-off valve 2063c arranged midway along the purge flow path 2063a. The on-off valve 2063c is an electromagnetic valve. The purge gas supply device 2063 supplies a purge gas (here, nitrogen gas) to the front chamber 2060, which has been degassed by the vacuum pump 2062b and placed in a negative pressure state.

[0176] (oil tank) The oil tank 70 includes a heater 2072 for heating the oil, an agitator (not shown) for agitating the oil, and a heat exchanger (not shown) for cooling the oil.

[0177] (Lifting device) The lifting device 2090 includes a rail 2093 extending in the vertical (perpendicular) direction, an elevator body 2092 guided in the vertical (perpendicular) direction by the rail 2093, and a drive mechanism 2094 that moves the elevator body 2092 up and down. A guide rail 2064 that guides or holds the transport tray C is arranged inside the elevator body 2092.

[0178] (Carburizing chamber transport device) A carburizing chamber transfer device 2085 is disposed in the internal space formed by the oil tank 2070 and the front chamber 2060. The carburizing chamber transfer device 2085 includes a roller conveyor 2085a that guides the transfer tray C held on the guide rails 2064 of the front chamber 2060, a hook 2085b that grips the engaging portion Cx of the transfer tray C, a snake chain 2085c that moves the hook 2085b back and forth between the front chamber 2060 and the carburizing chamber 2010, and a drive source 2085d that drives the snake chain 2085c via a sprocket.

[0179] (carburizing chamber) The carburizing chamber 2010 is equipped with a heating device 2012 that heats the workpiece W in the carburizing chamber 2010a, and an agitator 2016 provided in the carburizing chamber 2010a. Guide rails 2064 are provided in the carburizing chamber 2010a, and the workpiece W is placed on the guide rails 2064 via a carrier tray C. The heating device 2012 serves as a heater 2012a that heats the carburizing chamber 2010a. The carburizing chamber 2010 is preferably provided with an exhaust path 2029 and an on-off valve 2029a for exhausting gas from the carburizing chamber 2010a when purging the carburizing chamber 2010a with a carrier gas. The carburizing chamber 2010 is also provided with an acetylene concentration measuring sensor 3000 that measures the concentration of acetylene in the interior atmosphere.

[0180] (raw gas supply device) A raw material gas supply device 2020 is connected to the carburizing chamber 2010, which supplies various gases to the carburizing chamber 2010a. The raw material gas supply device 2020 has a carburizing gas system 2021 through which carburizing gas flows, a carrier gas system 2022 through which carrier gas flows, and a carburizing chamber supply system 2024 that supplies the gases flowing through these systems 2021 and 2022 to the carburizing chamber 2010a. The raw material gas supply device 2020 also has a hydrocarbon supply source 2025 connected to the carburizing gas system 2021 and a nitrogen supply source 2026 connected to the carrier gas system 2022. In this embodiment, direct carburizing, in which the carbon contained in the carburizing gas directly penetrates the workpiece W, is performed under normal pressure, so the term "carburizing gas" is used instead of "enriched gas."

[0181] (hydrocarbon source) The hydrocarbon source 2025 is a gas cylinder that stores acetylene.

[0182] (Carburizing gas system) The carburizing gas system 2021 has a supply pipe 2021a connected to a hydrocarbon supply source 2025, and an on-off valve 2021b and a flow meter 2021c provided on the supply pipe 2021a. The supply pipe 2021a is connected to the hydrocarbon supply source 2025, and carburizing gas from the hydrocarbon supply source 2025 flows through it. The on-off valve 2021b is a solenoid valve provided midway along the supply pipe 2021a. The on-off valve 2021b opens and closes the flow path and adjusts the flow rate of the carburizing gas. The flow meter 2021c is provided on the supply pipe 2021a downstream of the on-off valve 2021b and measures the flow rate of the carburizing gas flowing through the supply pipe 2021a. Note that the on-off valve 2021b only opens and closes the flow path, and a flow rate adjustment valve (not shown) that adjusts the flow rate of the carburizing gas may be provided separately from the on-off valve 2021b.

[0183] (nitrogen source) The nitrogen supply source 2026 generates a nitrogen-containing gas. This nitrogen-containing gas serves as a carrier gas. The nitrogen supply source 2026 includes a gas separator 2026a, which is a PSA-type nitrogen gas generator in this embodiment.

[0184] (Carrier gas system) The carrier gas system 2022 includes a supply pipe 2022a, an on-off valve 2022b, and a flowmeter 2022c. A first end of the supply pipe 2022a is connected to a gas mixer 2027 for adding carburizing gas, and a second end of the supply pipe 2022a is connected to a connection 2040 of the carburizing chamber supply system 2024. The carrier gas system 2022 also includes a gas mixer 2027. This gas mixer 2027 is located upstream of the on-off valve 2022b and the flowmeter 2022c and serves to add a small amount of carburizing gas to the carrier gas (nitrogen gas) from the nitrogen supply source 2026 as needed. The gas mixer 2027 can adjust the amount of carburizing gas added by referring to the carburizing gas flow rate output from the flowmeter 2027a. In this embodiment, oxygen is prevented from entering the carburizing chamber 2010, so adding carburizing gas is not necessary during normal operation. If oxygen or water enters the carburizing chamber 2010 for some reason, they can be reduced by adding a small amount of carburizing gas to the carrier gas. For example, when using a material other than liquid nitrogen as the carrier gas, there is a possibility that the nitrogen will contain a small amount of oxygen, so adding a small amount of acetylene to the carrier gas can suppress oxidation of the carrier gas by oxygen.

[0185] Carrier gas flows through the supply pipe 2022a. This carrier gas is guided to a connection 2040 of a supply system 2024 inside the carburizing chamber. The on-off valve 2022b is a solenoid valve and is provided midway along the supply pipe 2022a. The on-off valve 2022b opens and closes the flow path and adjusts the flow rate of the carrier gas. The flow meter 2022c is provided on the supply pipe 2022a downstream of the on-off valve 2022b and measures the flow rate of the carrier gas flowing through the supply pipe 2022a. Note that the on-off valve 2022b only opens and closes the flow path, and a flow rate adjustment valve (not shown) that adjusts the flow rate of the carrier gas may be provided separately from the on-off valve 2022b.

[0186] When only carrier gas is supplied to the carburizing chamber 2010a, the gas mixer 2027 is stopped, the on-off valve 2022b of the carrier gas system 2022 is opened, and the on-off valve 2021b of the carburizing gas system 2021 is closed. The supply flow rate of the carrier gas is not particularly limited, and may be set appropriately depending on the volume of the carburizing chamber 2010a, the surface area of ​​the workpiece W, the hardening depth required for the workpiece W, etc.

[0187] (Carburizing indoor supply system) The carburizing chamber supply system 2024 has a connection part 2040, and a first branch part 2041 and a second branch part 2042 that branch off from the connection part 2040. A supply pipe 2021a of the carburizing gas system 2021 and a supply pipe 2022a of the carrier gas system 2022 are connected to the upstream side of the connection part 2040. A mixer 2049 is provided midway through the connection part 2040. The mixer 2049 has the function of mixing the carburizing gas supplied from the upstream carburizing gas system 2021 and the carrier gas supplied from the carrier gas system 2022.

[0188] A first gas supply nozzle 2043 is provided at the tip of the first branch portion 2041, and a second gas supply nozzle 2044 is provided at the tip of the second branch portion 2042. The first gas supply nozzle 2043 is provided at the top of the carburizing chamber 2010. The first gas supply nozzle 2043 has a first supply port 2043a that opens into the carburizing chamber 2010a of the carburizing chamber 2010. The second gas supply nozzle 2044 is provided at the bottom of the carburizing chamber 2010. The second gas supply nozzle 2044 has a second supply port 2044a that opens into the carburizing chamber 2010a of the carburizing chamber 2010. Carburizing gas from the carburizing gas system 2021 is sprayed (or flows out) downward from the first supply port 2043a. Furthermore, carburizing gas from the carburizing gas system 2021 is sprayed upward from the second supply port 2044a.

[0189] The first branch portion 2041 and the second branch portion 2042 are provided with on-off valves 2041a and 2042a and flow meters 2041b and 2042b, respectively. These on-off valves 2041a and 2042a are solenoid valves that adjust the flow rates of gas flowing through the first branch portion 2041 and the second branch portion 2042, thereby making it possible to adjust the ratio of the flow rates of gas flowing through the first branch portion 2041 and the second branch portion 2042. The on-off valves 2041a and 2042a may be provided on only one of the first branch portion 2041 and the second branch portion 2042. Alternatively, the on-off valves 2041a and 2042a may only open and close the flow path, and a flow rate adjustment valve (not shown) that adjusts the flow rate of gas flowing through the first branch portion 2041 and the second branch portion 2042 may be provided separately from the on-off valves 2041a and 2042a.

[0190] (Control device) The control device 2030 controls the entire gas carburizing device. The operations realized by the control device 2030 will be described below.

[0191] (Pre-room loading process) The control device 2030 opens the front room entrance door 2050 and closes the front room second entrance door 2066, and loads the workpiece W from the external area into the front room 2060. During the loading, outside air (oxygen, nitrogen, water) enters the front room 2060.

[0192] (Pre-purging) In the pre-purge process performed after the antechamber loading process, the antechamber entrance door 2050 and the antechamber second entrance door 2066 are closed, and the vacuum pump (negative pressure generating source) 2062b is used to suck out the internal gas from the antechamber 2060 into which the workpiece W has been loaded for 5 minutes or more and 30 minutes or less, preferably 10 minutes or more and 20 minutes or less, thereby creating a negative pressure state while discharging the air that has entered. Thereafter, purge gas (nitrogen gas) is supplied to the antechamber 2060, which is in a negative pressure state, to restore the antechamber 2060 to normal pressure or a pressure higher than normal pressure. As a result, the antechamber 2060 is filled with purge gas (nitrogen gas).

[0193] (Carburizing chamber preparation) As part of the carburizing chamber preparation process, a carrier gas (nitrogen gas) is supplied to the carburizing chamber 2010, and the carburizing chamber 2010 is purged with the carrier gas (carburizing chamber purging process). As a result, the carburizing chamber 2010 is filled with the purge gas (nitrogen gas). The carburizing chamber 2010 is then heated to a carburizing temperature T1 (see FIG. 3) of 800°C or higher, and the workpiece W is ready to be loaded. For example, the carburizing temperature T1 is preferably controlled within the range of 880°C to 950°C. The carburizing chamber preparation process is preferably performed simultaneously with or before the pre-purging process.

[0194] (Carburizing chamber loading process) After the pre-purging process and the carburizing chamber preparation process are completed, the carburizing chamber loading process is performed. With the front-chamber access door 2050 closed, the front-chamber second access door 2066 and the heat-insulating door 2084 are opened, and the workpiece W in the front-chamber 2060 is moved to the carburizing chamber 2010. At this time, the nitrogen gas in the front-chamber 2060 and the nitrogen gas in the carburizing chamber 2010 mix with each other.

[0195] (Carburizing and diffusion treatment) In the carburizing process performed following the carburizing chamber loading process, the front chamber second access door 2066 and the heat-insulating door 2084 are closed, and a carrier gas (nitrogen gas) and a carburizing gas (acetylene) are supplied to the carburizing chamber 2010 while the workpiece W is heated, thereby carburizing the workpiece W. During this process, feedback control is performed using measurement data from the acetylene concentration measurement sensor 3000 to control the average acetylene concentration in the atmosphere in the carburizing chamber 2010 to a range of 0.10% by volume or more and 0.25% by volume or less. This allows almost all of the acetylene supplied to the carburizing chamber 2010 to be adsorbed and decomposed by the workpiece W, thereby reducing the amount of excess acetylene that flows outside. On the other hand, if the acetylene concentration in the atmosphere of the carburizing chamber 2010 is too low, acetylene shortages will occur in some locations, which can easily result in uneven carburizing. Therefore, it is preferable to maintain the average acetylene concentration at 0.10% by volume or more. After the carburizing process is completed, the supply of the carburizing gas is stopped and only the carrier gas is supplied.

[0196] A time chart of the carburizing process of the second embodiment is shown in Fig. 15. The carburizing chamber 10a is maintained at a preset carburizing temperature T1. When the workpiece W, which is adjusted to a preparation temperature T0 in the antechamber 2060, is carried into the carburizing chamber 2010a, the workpiece W is quickly heated to the carburizing temperature T1 (actual temperature rise time t x Once the workpiece W reaches the carburizing temperature (a temperature suitable for carburizing), the heating device 2012 is controlled to maintain the carburizing temperature. After the predetermined soaking time t5 based on the carburizing temperature has elapsed, the on-off valve 2021b of the carburizing gas system 2021 is controlled to start supplying carburizing gas to the carburizing chamber 2010a. This supplies a mixture of carrier gas and carburizing gas to the carburizing chamber 2010a. During this time, the carburizing chamber 2010a is maintained at atmospheric pressure. During the carburizing process, the average acetylene concentration in the atmosphere is controlled to a range of 0.10% by volume or more and 0.25% by volume or less. The flow rate of the carrier gas per hour is preferably controlled to 0.5 to 5.0 times the volume of the carburizing chamber 2010a. The flow rate of the carburizing gas is preferably controlled to 5 to 50 (L / min), taking into account the surface area of ​​the workpiece W. The carburizing gas is supplied continuously or intermittently during the predetermined carburizing time t2.

[0197] (Diffusion treatment) After the supply of the carburizing gas, the carburizing chamber 2010a is maintained at the carburizing temperature T1 with only the carrier gas being supplied for a predetermined diffusion time t4 as a diffusion process. During this time, the carbon that has penetrated into the workpiece W diffuses appropriately, forming a hardened layer of the desired thickness (carburization depth).

[0198] (Temperature reduction, quenching and holding treatment) After the diffusion time t3 has elapsed, the heating device 12 is controlled to lower the temperature inside the carburizing chamber 2010a to a preset quenching holding temperature T2 (actual temperature lowering time t yThe quenching temperature T2 is preferably within the range of 800°C to 880°C. The temperature inside the carburizing chamber 2010a is maintained at the quenching temperature T2 for a preset quenching time t6. In the carburizing chamber unloading process described below, once the workpiece W inside the carburizing chamber 2010 is unloaded into the antechamber 2060, the temperature is returned to the carburizing temperature T1 in preparation for the next carburizing process.

[0199] (Carburizing chamber removal process) In the carburizing chamber removal process, which is carried out following the temperature-lowering and quenching holding process, the front chamber second access door 2066 and the heat-insulating door 2084 are opened, and the workpiece W in the carburizing chamber 2010 is moved to the front chamber 2060. At this time, since the carburizing chamber 2010 and the front chamber 2060 are already filled with nitrogen gas, the nitrogen gas in both spaces mixes with each other. Once the movement of the workpiece W is complete, the front chamber second access door 2066 and the heat-insulating door 2084 are closed.

[0200] (Hardening treatment) In the quenching process, which is performed following the carburizing chamber removal process, the workpiece W in the anterior chamber 2060 is immersed in oil in the oil tank 2070 connected to the anterior chamber 2060 and rapidly cooled (quenching process). During this process, the oil vaporizes and turns into oil smoke, which fills the anterior chamber 2060. The workpiece W is immersed in the oil tank 2070 for an oil quenching time t7. The oil in the oil tank 2070 is maintained at a preset quenching temperature T3. The quenching temperature T3 is preferably in the range of 50°C to 200°C. For example, cold oil is typically around 60°C, semi-hot oil is typically around 120°C, and hot oil is typically around 150°C.

[0201] (oil draining treatment) As an oil-draining process that is carried out following the quenching process, the workpiece W is moved from the oil tank 2070 to the front chamber 2060 and left there for a while to drain the oil.

[0202] (Post-purge processing section) In the post-purging process that is performed following the quenching process and / or the oil-sinking process, the front chamber entrance door 2050 and the front chamber second entrance door 2066, which are already closed, are kept closed, and the gas in the front chamber 2060 during the quenching process of the workpiece W and / or the front chamber 2060 during the oil-sinking process is sucked out by a vacuum pump (negative pressure generating source) 2062b, thereby creating a negative pressure state while discharging nitrogen gas and vaporized oil (oil smoke), and then purge gas (nitrogen gas) is supplied to the front chamber 2060 in the negative pressure state, and the front chamber 2060 is restored to normal pressure or a state higher than normal pressure. As a result, the front chamber 2060 is again filled with only purge gas (nitrogen gas).

[0203] (Pre-room removal processing) In the front chamber unloading process that is executed following the post-purging process, the front chamber entrance door 2050 is opened and the front chamber second entrance door 2066 is closed, and the workpiece W is unloaded from the front chamber 2060 to an external area. [Example]

[0204] The inventors of the present invention conducted a first experiment to verify the appropriate acetylene concentration in the atmospheric gas during carburizing using the batch processing type gas carburizing apparatus of the second embodiment. The first experiment aimed to verify the lower limit of the acetylene concentration.

[0205] First, the inventors prepared two three-tiered stands as shown in FIG. 1(B), and placed five experimental workpieces, as shown in FIG. 16(A), on each tier. The experimental workpieces were cylindrical bodies made of metal. Then, carburizing treatment was performed under different conditions on each of the two stands, and then quenching treatment was performed. The experimental workpieces on the first stand were subjected to the first carburizing treatment, and the experimental workpieces on the second stand were subjected to the second carburizing treatment.

[0206] (Time chart for the first carburizing process) In the first carburizing treatment for the first frame, as shown in Figure 16(B), the carburizing temperature T1 was set to 900°C, the quenching holding temperature T2 was set to 850°C, the soaking time t5 in the temperature-raising treatment was set to 20 minutes, the carburizing time t2 in the carburizing gas supply treatment was set to 58 minutes, the diffusion time t3 in the diffusion treatment was set to 80 minutes, and the quenching holding time t6 in the temperature-lowering treatment was set to 20 minutes. Nitrogen gas was used as the carrier gas supplied to the carburizing chamber, and the flow rate was set to 3 (Nm 3 / Hr). In addition, acetylene-containing gas was used as the carburizing gas in the carburizing gas supply process, and its flow rate was set to 3 (NL / M). By adjusting these factors, the acetylene concentration in the atmosphere in the carburizing chamber during the carburizing process was controlled to less than 0.10% by volume, specifically about 0.05% by volume. For the quenching process, the quenching temperature T3 was set to 170°C, and the specimen was immersed in an oil bath for 15 minutes, after which the oil was drained off.

[0207] (Time chart for the second carburizing process) In the second carburizing treatment for the second stand, as shown in Figure 16(C), the carburizing temperature T1 was set to 900°C, the quenching holding temperature T2 was set to 850°C, the soaking time t5 in the temperature-raising treatment was set to 20 minutes, the carburizing time t2 in the carburizing gas supply treatment was set to 58 minutes, the diffusion time t3 in the diffusion treatment was set to 80 minutes, and the quenching holding time t6 in the temperature-lowering treatment was set to 20 minutes. Nitrogen gas was used as the carrier gas supplied to the carburizing chamber, and the flow rate was set to 3 (Nm 3 / Hr). In addition, acetylene-containing gas was used as the carburizing gas in the carburizing gas supply process, and its flow rate was set to 10 (NL / M). By adjusting these settings, the acetylene concentration in the atmosphere in the carburizing chamber during the carburizing process was controlled to be 0.10% by volume or more, specifically 0.22% by volume. In the subsequent quenching process, the quenching temperature T3 was set to 170°C, and the specimen was immersed in an oil bath for 15 minutes, after which the oil was drained off.

[0208] Then, a Vickers hardness test was performed on each of the experimental workpieces on the first stand and on each of the experimental workpieces on the second stand to measure the surface hardness and cross-sectional hardness. The results are shown in Figures 17 and 18.

[0209] Figure 17(A) is a table showing the results of the surface hardness of each of the experimental workpieces (No. 1 to No. 15) on the first stand. Figure 17(B) is a table showing the results of the cross-sectional hardness of experimental workpieces No. 1, No. 7, No. 8, and No. 15 on the first stand. Figure 18 is a graph showing the acetylene concentration and hydrogen concentration of the experimental workpiece on the first stand and the space around it.

[0210] Looking at the table in Figure 17(A), the surface hardness values ​​of experimental workpieces No. 7 and No. 8 are low. Looking at the tables in Figure 17(B) and (C), the hardness values ​​of experimental workpieces No. 1 and No. 15 decrease from the surface toward the interior, and the rate of decrease (the slope of the graph) is large. On the other hand, experimental workpieces No. 7 and No. 8 decrease slightly from the surface toward the interior, but the rate of decrease (the slope of the graph) is quite small.

[0211] From the above, it can be seen that the experimental workpieces on the first stand, which had undergone carburizing and quenching treatments, included some with differences in surface hardness and cross-sectional hardness, resulting in variations in quality stability.

[0212] Furthermore, when acetylene is adsorbed onto the experimental workpiece, it is decomposed into carbon and hydrogen according to the relationship (C2H2 → 2C + H2). As shown in Figure 18, in the space including the first stand where the carburizing gas supply process is performed and its surroundings, the concentration of hydrogen increases over time (i.e., the carburizing process is progressing), and acetylene is detected in the atmosphere. In other words, since there is surplus acetylene in the atmosphere, it can be inferred that the carburizing process using acetylene is certainly continuing (continuing). However, when the acetylene concentration in this atmosphere is low, at around 0.05% by volume, the inventor's verification has revealed that "variation" is likely to occur in the carburizing process, as shown in Figure 17.

[0213] Figure 19(A) is a table showing the results of the surface hardness of each of the experimental workpieces (No. 1 to No. 15) on the second stand when the acetylene concentration in the atmosphere was controlled to 0.10% by volume or more. Figure 19(B) is a table showing the results of the cross-sectional hardness of the experimental workpieces No. 1, No. 7, No. 8, and No. 15 on the second stand.

[0214] Looking at the table in Figure 19(A), it can be seen that the entire test workpieces No. 1 to No. 15 have similar surface hardness values. Looking at the table in Figure 19(B), it can be seen that the hardness values ​​of the entire test workpieces No. 1 to No. 15 decrease from the surface toward the interior, and the rate of decrease (the slope of the graph) is large. Furthermore, the entire test workpieces No. 1 to No. 15 have a similar rate of decrease. In other words, there is no variation in quality, as with the test workpieces on the first stand shown in Figure 17.

[0215] From the above results, it was confirmed that if the acetylene concentration of the mixed gas used in the carburizing gas supply process is 0.10% by volume or more, the surface hardness and cross-sectional hardness of multiple workpieces can be kept constant even when the carburizing process is performed. [Example]

[0216] The inventors of the present invention conducted a second experiment to verify the appropriate acetylene concentration in the atmospheric gas during carburizing using the batch processing type gas carburizing apparatus of the second embodiment. The purpose of the second experiment was to verify the upper limit of the acetylene concentration.

[0217] First, the inventors prepared two stacked cages, each consisting of 10 cages stacked high, each capable of holding 15 experimental workpieces, as shown in the photographs in Figures 20(A) and (B). The experimental workpieces were annular plates made of SPCC (Steel Plate Cold Commercial). Then, carburizing and quenching treatments were performed on each of the two stacked cages under different conditions. The experimental workpieces in the first stacked cage were subjected to the third carburizing treatment, and the experimental workpieces in the second stacked cage were subjected to the fourth carburizing treatment.

[0218] (Time chart for the third carburizing treatment) As shown in FIG. 21(A), in the third carburizing treatment for the first stacked cage, the carburizing temperature T1 was set to 900°C, the quenching holding temperature T2 was set to 850°C, the soaking time t5 in the temperature rising treatment was set to 20 minutes, the carburizing time t2 in the carburizing gas supply treatment was set to 58 minutes, the diffusion time t3 in the diffusion treatment was set to 80 minutes, and the quenching holding time t6 was set to 20 minutes. Nitrogen gas was used as the carrier gas, and the flow rate was set to 3 (Nm 3 / Hr). Acetylene-containing gas was used as the carburizing gas, and the flow rate was 20 (NL / M) for the first 38 minutes of the carburizing gas supply process, and 15 (NL / M) for the remaining 20 minutes. This ensured that the acetylene concentration in the atmosphere exceeded 0.25% by volume for the first 38 minutes. Specifically, the acetylene concentration was controlled to 0.30% by volume. For the quenching process, the quenching temperature T3 was set to 120°C, and the specimen was immersed in an oil bath, after which the oil was drained off.

[0219] (Time chart for the fourth carburizing treatment) As shown in FIG. 21(B), in the fourth carburizing treatment for the second stacked cage, the carburizing temperature T1 was set to 900°C, the soaking time t5 in the temperature rising treatment was set to 20 minutes, the carburizing time t2 in the carburizing gas supply treatment was set to 58 minutes, and the diffusion time t3 in the diffusion treatment was set to 92 minutes. Nitrogen gas was used as the carrier gas, and the flow rate was set to 3 (Nm 3 / Hr). In addition, acetylene-containing gas was used as the carburizing gas, and the flow rate was set to 15 (NL / M) in the carburizing gas supply process. This controlled the acetylene concentration in the atmosphere during the carburizing process to be within the range of 0.10 volume % to 0.25 volume % (specifically, 0.15 volume %). In the quenching process, the quenching temperature T3 was set to 120°C, and the specimen was immersed in an oil bath, after which the oil was drained off.

[0220] Figure 22(A) is a photograph of three experimental workpieces in the first stacked cage that underwent the third carburizing treatment. Figure 22(B) is a photograph of three experimental workpieces in the second stacked cage that underwent the fourth carburizing treatment. As shown in Figure 22(A), a lot of soot can be seen on the surfaces of the three experimental workpieces in the first stacked cage. As shown in Figure 22(B), some soot can be seen on the surfaces of the three experimental workpieces in the second stacked cage, but this is within the acceptable range.

[0221] Figure 23 shows photomicrographs of a cross section near the surface of the first stacked cage test workpiece that underwent the third carburizing treatment, and a photomicrograph of a cross section near the surface of the second stacked cage test workpiece that underwent the fourth carburizing treatment. The photomicrographs include high-magnification and low-magnification ones. As shown in these photomicrographs, it was confirmed that good structure was obtained both near the surface and inside of each test workpiece.

[0222] From the above, it was confirmed that sooting beyond the allowable range can be prevented even when carburizing is performed, as long as the acetylene concentration in the atmosphere in the carburizing chamber is 0.25% by volume or less.

[0223] The carburizing and quenching treatments in Examples 1 and 2 are exemplified using the batch-processing gas carburizing apparatus of the second embodiment, but the same applies when the continuous-processing gas carburizing apparatus of the first embodiment is used. If the above carburizing and quenching treatments can be performed on experimental workpieces, it can be assumed that similar results to those described above will be obtained regardless of the type and method of equipment.

[0224] Next, a gas carburizing apparatus according to a third embodiment of the present invention will be described with reference to Fig. 24. In the third embodiment, components and processing steps similar to those in the continuous processing mode of the first embodiment will be denoted by the same reference numerals in the drawings to avoid redundant explanation, and the following description will focus on the differences.

[0225] (Overall composition) As shown in FIG. 24, the gas carburizing apparatus is connected to a measurement outlet line 1100 for extracting the atmosphere within the carburizing section S2 to the outside. This measurement outlet line 1100 is provided, in order from upstream to downstream, with an on-off valve 1110, a filter 1120, an air pump 1130, and an acetylene concentration measurement sensor 1000. The on-off valve 1110 controls whether or not to discharge the atmosphere from the measurement outlet line 1100 and adjusts the air flow rate. The filter 1120 purifies the atmosphere within the carburizing section S2 by adsorbing foreign matter (e.g., oil, dust, etc.). The air pump 1130 sucks in the atmosphere within the carburizing section S2, which is a normal pressure environment, and then pushes this atmosphere into the acetylene concentration sensor 1000. The air pump 1130 can also control the air flow rate. In the measurement outlet path 1100, the upstream side of the air supply pump 1130 tends to be a low-pressure environment section relative to atmospheric pressure, while the downstream side of the air supply pump 1130 tends to be a positive-pressure environment section relative to atmospheric pressure. The low-pressure environment section in the measurement outlet path 1100 carries the risk of drawing in air or the like through gaps in the piping. Therefore, it is preferable to shorten the low-pressure environment section by locating the air supply pump 1130 as upstream as possible.

[0226] The acetylene concentration measurement sensor 1000 is preferably, for example, an infrared absorption type concentration sensor. Specifically, the atmosphere passing through a predetermined cell (passage) is irradiated with laser light having a wavelength range including the peak of the optical absorption spectrum of acetylene by a laser light source or the like, the emitted light after multiple reflection by the cell is detected by a photodetector such as a quantum photoelectric element, and the signal is analyzed by an analyzer, thereby calculating the acetylene concentration. However, the acetylene concentration sensor 1000 is not limited to the above structure, and various measurement methods (detection methods) can be adopted.

[0227] The flow rate of the atmosphere drawn in by the on-off valve 1110 and / or the air pump 1140 is preferably set to 10% or less, more preferably 5% or less, of the total flow rate of the carrier gas and carburizing gas (acetylene) supplied to the carburizing section S2 by the carburizing section supply system 94. For example, if the total flow rate of the carrier gas and carburizing gas (acetylene) is 60 L / min, the flow rate of the atmosphere drawn out from the measurement outlet path 1100 should be 6 L / min or less, more preferably 3 L / min or less. Here, it is set to 1 L / min. This prevents the acetylene concentration measurement from adversely affecting the atmosphere in the carburizing section S2 itself.

[0228] In particular, in this embodiment, the air supply pump 1140 is located upstream of the acetylene concentration measurement sensor 1000 and guides the atmosphere extracted from the carburizing section S2 to the acetylene concentration measurement sensor 1000 under positive pressure. This places the concentration measurement sensor 1000 in a positive pressure environment, thereby improving the accuracy of acetylene measurement. As a result, the flow rate of the atmosphere extracted to the acetylene concentration measurement sensor 1000 can be set to 10% or less of the total flow rate of gas supplied to the carburizing section S2, which leads to stabilizing the diffusion state of the atmosphere within the carburizing section S2. At the same time, the small flow rate of the atmosphere extracted reduces the burden on the filter 1120 and reduces the frequency of maintenance and replacement. On the other hand, if the flow rate of the atmosphere extracted to the acetylene concentration measurement sensor 1000 is set to more than 10% of the total flow rate of gas supplied to the carburizing section S2, disturbances in the atmosphere within the carburizing section S2 may occur, potentially resulting in poor carburization in some locations within the carburizing section S2. Furthermore, since the amount of atmosphere discharged is large, the burden on the filter 1120 increases, and the frequency of maintenance and replacement increases.

[0229] Unlike the first embodiment, the carburizing section supply system 94 of this gas carburizing apparatus has a first branch portion 941, a second branch portion 942, a third branch portion 943, and a fourth branch portion 944 that branch out four ways from the output side of the mixer 93.

[0230] A first gas supply nozzle 941D is provided at the tip of the first branch portion 941, a second gas supply nozzle 942D is provided at the tip of the second branch portion 942, a first gas supply nozzle 943D is provided at the tip of the third branch portion 943, and a second gas supply nozzle 944D is provided at the tip of the fourth branch portion 944.

[0231] First branch section 941 to fourth branch section 944 each include branch pipes 941A, 942A, 943A, and 944A, on-off valves 941B, 942B, 943B, and 944B, and flow meters 941C, 942C, 943C, and 944C. These on-off valves 941B and 942B may be solenoid valves that perform ON / OFF control or motor-operated valves (mass flow meters) that can control the flow rate. The on-off valves 941B, 942B, 943B, and 944B can be used to adjust the flow rate of gas flowing through branch pipes 941A, 942A, 943A, and 944A.

[0232] The first gas supply nozzle 941D and the second gas supply nozzle 942D are provided at the top of the carburizing chamber 3 in the carburizing section S2. The third gas supply nozzle 943D and the fourth gas supply nozzle 944D are provided at the bottom of the carburizing chamber 3 in the carburizing section S2. The first gas supply nozzle 941D and the second gas supply nozzle 942D are provided at an interval in the transfer direction H2, and the third gas supply nozzle 943D and the fourth gas supply nozzle 944D are also provided at an interval in the transfer direction H2. Note that here, gas supply nozzles are provided at both the top and bottom of the carburizing chamber 3, but gas supply nozzles may also be provided on, for example, the left and right side surfaces of the carburizing chamber 3 in the transfer direction H2. Furthermore, for example, providing nozzles at both the top and side surfaces is preferable, and more preferably, gas supply nozzles are provided at all of the top, bottom, and side surfaces.

[0233] As already mentioned, acetylene, which is the carburizing gas, decomposes (carburizes) the workpiece W extremely quickly. Therefore, acetylene sprayed into the carburizing section S2 from the first to fourth gas supply nozzles 941D to 944D is adsorbed to and decomposed on the workpiece W closest to each nozzle, making it less likely to diffuse to other areas. Furthermore, if an atmosphere is drawn out from the measurement outlet path 1100 to measure the acetylene concentration, this disturbance could adversely affect the diffusion of acetylene within the carburizing section S2. Therefore, as in this embodiment, acetylene is directly directed at the workpiece W from multiple directions arbitrarily selected from above, below, left, and right, thereby stabilizing the carburizing quality.

[0234] (feedback control) The control device 100 refers to the acetylene concentration detected by the acetylene concentration measuring sensor 1000 and performs feedback control so that the acetylene concentration falls within a predetermined target value (a time average value or a constant value in the range of 0.10% by volume or more and 0.25% by volume or less).

[0235] Specifically, the control device 100 controls the on-off valve 92B of the carrier gas system 92 and the on-off valve 90B of the carburizing gas system 90 to adjust the mixture ratio of the carburizing gas (acetylene) to the carrier gas and the total flow rate of both gases. In addition, by controlling the on-off valves 941B, 942B, 943B, and 944B, the total flow rate of the mixed gas of the carrier gas and the carburizing gas (acetylene) can also be adjusted.

[0236] At the same time, it is preferable that the control device 100 controls the total flow rate of the mixed gas of the carrier gas and carburizing gas (acetylene) supplied to the carburizing chamber 3A to be at least 10 times the flow rate of the atmosphere sucked (exhausted) from the carburizing chamber 3A by the air supply pump 1140. For example, if the suction flow rate by the air supply pump 1140 is 1 (L / min), the control device 100 controls the supply so that the total flow rate of the mixed gas is 10 (L / min) or more. This makes it possible to stabilize the carburizing quality.

[0237] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments, but is limited only by the claims. [Explanation of symbols]

[0238] 1 External area 2. Front room 3 Carburizing chamber 3A Carburizing chamber 4. Quenching chamber 4A Oil drain area 4B Oil tank 5A First Connection 5B Second connecting road 6 Workpiece removal area 9. Raw material gas supply device 10 Control device 12 Heating device 16 Mixer 20A Front room entrance 20B Anteroom exit 22 Front room entrance door 23 Reciprocating drive mechanism 24 Front room exit door 25 Reciprocating drive mechanism 27 Transport path 30A Carburizing chamber entrance 30B Carburizing chamber outlet 31 Heating device 31A heater 32A Insulated entrance door 32B Insulated Exit Door 33A Reciprocating drive mechanism 33B Reciprocating drive mechanism 34 Mixer 36 Exhaust duct 36A On-off valve 37 Partition Wall 40 Lifting device 40A Quenching room entrance 40B Quenching chamber exit 42A Quenching room entrance door 42B Quenching chamber exit door 43 Rail 43a First supply port 44 Elevator body 44a Second supply port 45 Drive mechanism 46 Heater 47 Mixer 48 Heat exchanger 49 Mixer 49A Reciprocating Drive Mechanism 49B Reciprocating drive mechanism 70 Anteroom transport device 70A Roller Conveyor 70B hook 70C snake chain 70D drive unit 71 Carburizing chamber transport device 71A Pressing device 71B Piston rod 72 Work moving mechanism 73 Quenching chamber transport device 74 Unloading device 80 Anterior chamber negative pressure generating device 81 Vacuum Pump 82 Degassing channel 83 On-off valve 84 Front chamber purge gas supply device 85 Purge flow path 86 On-off valve 87 Hardening chamber negative pressure generating device 87A Vacuum Pump 87B Degassing channel 87C On-off valve 89 Quenching chamber purge gas supply device 89A Purge flow path 89B On-off valve 90 Carburizing gas system 90A supply pipe 90B On-off valve 90C flow meter 91 Gas Mixer 91A Supply Pipe 91B Flowmeter 92 Carrier gas system 92A Supply Pipe 92B On-off valve 92C flow meter 93 Mixer 94 Carburizing indoor supply system 96 Hydrocarbon Sources 98 Nitrogen Source 98A Gas Separator 100 control device 101 CPU 102 memory 103 Information storage medium 104 Communication Interface 110 Pre-chamber transport processing unit 111 Front room entrance door opening / closing processing unit 112 Front room exit door opening / closing processing unit 113 Front chamber degassing treatment unit 114 Front chamber purge processing section 115 Insulated entrance door opening / closing processing section 116 Insulated exit door opening / closing processing section 117 Carrier gas control section 118 Carburizing gas control unit 119 Carburizing chamber transport control unit 120 Carburizing chamber agitation processing section 121 Heat treatment section inside the carburizing chamber 122 Quenching chamber entrance door opening / closing processing section 123 Quenching chamber exit door opening / closing processing section 124 Quenching chamber transport control unit 125 Lifting processing section 126 Oil tank heater processing section 127 Oil Tank Cooling Processing Unit 128 Oil tank agitation processing section 129 Quenching chamber degassing processing section 130 Quenching chamber purge processing section 131 Work carry-out control unit 150 Front room loading processing section 152 Front chamber purge control unit 154 Carburizing chamber preparation processing section 156 Carburizing chamber loading section 158 Carburizing Treatment Section 160 Hardening Room Main Purge Control Section 162 Quenching chamber loading section 164 Hardening processing section 166 Oil cutting processing section 168 Quenching room pre-purge management department 170 Work removal processing section 171 Overall temperature control department 172 Fully automated processing unit 941 First Branch 941A Branch Pipe 941B On-off valve 941C flow meter 941D First gas supply nozzle 941E First supply port 942 Second Branch 942A Branch Pipe 942B On-off Valve 942C flow meter 942D Secondary Gas Supply Nozzle 942E Second supply port 1000 Acetylene concentration measurement sensor

Claims

1. a carburizing chamber in which the workpiece is heated under atmospheric pressure or a pressure higher than atmospheric pressure; a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber; Equipped with an average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.25% by volume or less; Gas carburizing equipment.

2. a carburizing chamber in which the workpiece is heated under atmospheric pressure or a pressure higher than atmospheric pressure; a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber; Equipped with The average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.10% by volume or more. Gas carburizing equipment.

3. a carburizing chamber in which the workpiece is heated under atmospheric pressure or a pressure higher than atmospheric pressure; a raw material gas supply device that supplies a mixed gas of a carrier gas and a carburizing gas containing acetylene to the carburizing chamber; Equipped with an average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is 0.10% by volume or more and 0.25% by volume or less; Gas carburizing equipment.

4. A gas carburizing method for carburizing a workpiece by supplying a mixed gas of a carrier gas and a carburizing gas to the workpiece, comprising: The carburizing gas includes acetylene, The average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to 0.25% by volume or less. Gas carburizing method.

5. A gas carburizing method for carburizing a workpiece by supplying a mixed gas of a carrier gas and a carburizing gas to the workpiece, comprising: The carburizing gas includes acetylene, The average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to 0.10% by volume or more. Gas carburizing method.

6. A gas carburizing method for carburizing a workpiece by supplying a mixed gas of a carrier gas and a carburizing gas to the workpiece, comprising: The carburizing gas includes acetylene, The average concentration of acetylene contained in the atmosphere of the carburizing chamber during the carburizing treatment of the workpiece is set to 0.10% by volume or more and 0.25% by volume or less. Gas carburizing method.

7. a carburizing chamber in which the workpiece is heated under atmospheric pressure or a pressure higher than atmospheric pressure; a raw material gas supply device that supplies a carrier gas and a carburizing gas containing acetylene to the carburizing chamber; an acetylene concentration measuring device for detecting the concentration of acetylene contained in the atmosphere in the carburizing chamber while the workpiece is being carburized; a control device that performs feedback control of the amount of acetylene supplied by the raw material gas supply device by referring to the concentration measured by the acetylene concentration measuring device so that the concentration of acetylene contained in the atmosphere in the carburizing chamber becomes a target value; characterized in that it comprises Gas carburizing equipment.

8. the raw material gas supply device adjusts the concentration of acetylene contained in the atmosphere in the carburizing chamber by adjusting the supply amount of the mixed gas of acetylene and a carrier gas or the mixing ratio of acetylene in the mixed gas of acetylene and a carrier gas.

8. The gas carburizing apparatus according to claim 7.

9. a measurement outlet path for leading the atmosphere of the carburizing chamber out of the carburizing chamber; an air pump provided midway through the measurement outlet path; Further provided with the acetylene concentration measuring device is disposed downstream of the air pump in the measurement outlet path, 9. The gas carburizing apparatus according to claim 7 or 8.

10. a flow rate of the atmosphere discharged from the carburizing chamber by the gas supply pump being 10% or less of the total flow rate of the gas supplied to the carburizing chamber by the raw material gas supply device; 10. The gas carburizing apparatus according to claim 9.

11. the control device controls the average concentration of acetylene contained in the atmosphere of the carburizing chamber to 0.25% by volume or less during the carburizing treatment of the workpiece.

9. The gas carburizing apparatus according to claim 7 or 8.

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