Atmospheric furnace and method of using the atmosphere furnace

Abstract

To provide an atmosphere furnace capable of controlling an atmosphere about a dew point using a nitrogen gas and a hydrogen gas as atmosphere gases, and a method for using an atmosphere furnace.SOLUTION: An atmosphere furnace 10 is used for heat-treating an object to be treated in an in-furnace atmosphere charged with a hydrogen gas and a nitrogen gas as atmosphere gases, and comprises: a furnace body 11 for storing the object to be treated; a hydrogen gas feed system 12 connected to the furnace body 11; a nitrogen gas feed system 13 connected to the furnace body 11; a PSA type nitrogen gas production device 16 connected to the nitrogen gas feed system 13 to remove oxygen from the air to produce a nitrogen gas; a dew point meter 17 fitted to the furnace body 11 to measure a dew point temperature in the furnace; and a controller 18 for controlling the dew point temperature in accordance with the dew point temperature obtained from the dew point meter 17. The controller 18 adjusts the purity of the nitrogen gas produced by the PSA type nitrogen gas production device 16, increases or reduces the amount of oxygen fed into the furnace body 11, combined with the nitrogen gas, and increases or reduces the amount of moisture produced in the in-furnace atmosphere through a reaction between the oxygen and the hydrogen gas, thereby controlling the dew point temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an atmospheric furnace that uses an inert gas and hydrogen gas as atmospheric gases and is capable of adjusting the dew point temperature inside the furnace, and a method for using the atmospheric furnace. [Background technology]

[0002] Metallic workpieces are heat-treated for various purposes, such as removing internal stress, adjusting hardness, and improving workability. Heat treatment is carried out using an atmosphere furnace, in which the atmosphere, temperature, dew point temperature (hereinafter simply referred to as "dew point"), and other environmental conditions are adjusted according to the purpose. Atmospheric furnaces use atmospheric gases to create an atmosphere that prevents oxidation and decarbonization of the workpieces. Typically, petroleum-based gases such as DX gas and RX gas, which are obtained by transforming propane gas, are used as the atmospheric gas. Among heat treatments, brazing, bright annealing, and the like require an environment that prevents oxidation of the workpiece and has a high dew point, and an atmospheric furnace that uses a reducing gas or the like as the atmospheric gas and allows for dew point adjustment is used. The vertical continuous annealing furnace described in Patent Document 1 is configured so that a high dew point gas containing water vapor is blown into the furnace as atmospheric gas, and the dew point is adjusted by controlling the amount of high dew point gas blown in. The reducing atmosphere furnace described in Patent Document 2 uses a reducing gas consisting of nitrogen gas and hydrogen gas as the atmospheric gas, and adjusts the dew point by mixing the reducing gas with a gas containing oxygen and controlling the oxygen concentration in the reducing gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-173144 [Patent Document 2] Japanese Patent Publication No. 2020-190017 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, atmospheric furnaces have been required to be decarbonized due to growing environmental awareness, such as carbon neutrality, and studies have been conducted to avoid the use of petroleum-based gases and use inert gases such as nitrogen gas and hydrogen gas as atmospheric gases. Patent Document 1 does not take such studies into consideration. Patent Document 2 uses nitrogen gas and hydrogen gas as atmospheric gases, but lists air as a gas containing oxygen, which is insufficient consideration because air contains substances such as carbon dioxide that inhibit decarbonization. Furthermore, in atmospheric furnaces that use hydrogen gas as the atmospheric gas, it is difficult to control the atmosphere with respect to the dew point, and this can easily affect the quality of the workpieces, such as causing the workpieces to stick together (diffusion bonding, adhesion), poor bonding in brazing processes, and reduced or lost brightness in bright annealing processes.

[0005] The present invention aims to solve the problems associated with the prior art, and aims to provide an atmospheric furnace and a method for using the atmospheric furnace that uses nitrogen gas and hydrogen gas as atmospheric gases and that can control the atmosphere with respect to the dew point. [Means for solving the problem]

[0006] In order to solve the above problems, the invention described in claim 1 is an atmospheric furnace for heat-treating a workpiece in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body that accommodates the workpiece; a hydrogen gas supply system connected to the furnace body; a nitrogen gas supply system connected to the furnace body; a PSA nitrogen gas production device connected to the nitrogen gas supply system and producing nitrogen gas by removing oxygen from air; a dew point meter attached to the furnace body to measure a dew point temperature inside the furnace; a controller that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter; The controller adjusts the purity of the nitrogen gas produced by the PSA nitrogen gas production system, increases or decreases the amount of oxygen mixed with the nitrogen gas and sent into the furnace of the furnace body, and increases or decreases the amount of moisture generated in the atmosphere inside the furnace by the reaction between the oxygen and the hydrogen gas, thereby controlling the dew point temperature. The invention described in claim 2 is an atmospheric furnace for heat-treating a workpiece in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body that accommodates the workpiece; a hydrogen gas supply system connected to the furnace body; a nitrogen gas supply system connected to the furnace body; a moisture supply system connected to the furnace body to supply moisture into the furnace, and a control valve connected to the moisture supply system; a dew point meter attached to the furnace body to measure a dew point temperature inside the furnace; a controller that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter; The controller controls the dew point temperature by operating the control valve and adjusting the amount of moisture supplied from the moisture supply system in accordance with the dew point temperature obtained from the dew point meter. The invention described in claim 3 is the invention described in claim 1 or 2, wherein the furnace body includes a heating chamber for heating the workpiece and a cooling chamber for cooling the workpiece, the hydrogen gas supply system and the nitrogen gas supply system are connected to the heating chamber; The cooling chamber and the heating chamber are internally connected to each other, and atmospheric gas is diverted from the heating chamber. The invention described in claim 4 is the invention described in claim 3, wherein an end of the furnace body at a side where the workpiece is inserted into the furnace is an inlet end, and an end at a side where the workpiece is removed from the furnace is an outlet end, a first gas exhaust system connected to an inlet end of the furnace body to exhaust gas from within the furnace, and a first exhaust valve connected to the first gas exhaust system to adjust the amount of exhaust; Further provided is a second gas exhaust system connected to the outlet end of the furnace body to exhaust gas from the furnace, and a second exhaust valve connected to the second gas exhaust system to adjust the exhaust amount, The controller adjusts the exhaust volume by operating the exhaust valves of at least one of the first gas exhaust system and the second gas exhaust system, thereby controlling the amount of atmospheric gas diverted from the heating chamber to the inlet end or the outlet end of the furnace body. The invention described in claim 5 is a method of using the atmosphere furnace described in claim 1 to perform a brazing treatment on a brazing material and a base material as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is set to 3 vol% or more and 30 vol% or less, The gist of this system is that the purity of the nitrogen gas produced by the PSA nitrogen gas production equipment is adjusted to 97% or more and 99.5% or less using a controller, thereby controlling the dew point temperature inside the furnace to 5°C or more and 40°C or less. The invention described in claim 6 is a method of using the atmosphere furnace described in claim 2 to perform a brazing treatment on a brazing material and a base material as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is set to 3 vol% or more and 30 vol% or less, The controller adjusts the amount of moisture supplied from the moisture supply system so that the moisture concentration in the atmosphere inside the furnace is between 0.8 vol% and 6.5 vol%, and the dew point temperature inside the furnace is controlled to between 5°C and 40°C. The invention described in claim 7 is a method for using the atmosphere furnace described in claim 2 to bright anneal a stainless steel workpiece as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is 50 vol% or more, The controller adjusts the amount of moisture supplied from the moisture supply system so that the moisture concentration in the atmosphere inside the furnace is between 0.008 vol% and 0.02 vol%, thereby controlling the dew point temperature inside the furnace to between -50°C and -45°C. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an atmospheric furnace and a method of using the atmospheric furnace, which use nitrogen gas and hydrogen gas as atmospheric gases and are capable of controlling the atmosphere with respect to the dew point. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an atmospheric furnace according to a first embodiment. [Figure 2] FIG. 4 is a schematic cross-sectional view showing an atmospheric furnace according to a second embodiment. [Figure 3] 4 is a flowchart showing a specific example of dew point control in the atmospheric furnace according to the first embodiment. [Figure 4] 10 is a flowchart showing a specific example of dew point control in an atmospheric furnace according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The matters set forth herein are for illustrative purposes only and are intended to provide an illustrative description of the embodiments of the present invention, with the aim of providing what is believed to be the most effective and easily understandable explanation of the principles and conceptual features of the present invention. In this respect, it is not intended to show structural details of the present invention beyond the extent necessary for a fundamental understanding of the present invention, and the description, taken together with the drawings, will make clear to those skilled in the art how some aspects of the present invention may be actually embodied.

[0010] [1] Atmospheric furnace (first form) The atmospheric furnace of the present invention is an atmospheric furnace 10 in which a workpiece is heat-treated in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body 11 that accommodates the object to be treated; a hydrogen gas supply system 12 connected to the furnace body 11; a nitrogen gas supply system 13 connected to the furnace body 11; a PSA nitrogen gas production device 16 connected to the nitrogen gas supply system 13 and producing nitrogen gas by removing oxygen from air; a dew point meter 17 attached to the furnace body 11 to measure the dew point temperature inside the furnace; a controller (18) that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter (17); The controller 18 controls the dew point temperature by adjusting the purity of the nitrogen gas produced by the PSA nitrogen gas production apparatus 16, increasing or decreasing the amount of oxygen mixed with the nitrogen gas and sent into the furnace of the furnace body 11, and increasing or decreasing the amount of moisture generated in the atmosphere inside the furnace by the reaction between the oxygen and the hydrogen gas (see Figure 1). The configurations of the furnace body 11, hydrogen gas supply system 12, nitrogen gas supply system 13, PSA nitrogen gas production device 16, dew point meter 17, and controller 18 included in the atmospheric furnace 10 of the first embodiment will be described below.

[0011] (1) Furnace body The furnace body 11 is used to house and heat-treat the object to be treated (see FIGS. 1 and 2). Heat treatments suitable for use with the furnace body 11 are not particularly limited as long as they require control of the dew point temperature (hereinafter also abbreviated as "dew point"), but examples thereof include brazing and bright annealing. The furnace body 11 may be any furnace as long as it is applicable to heat treatment, with respect to the method of processing and transporting the workpiece, the configuration, materials used, shape, size, furnace volume, heating and cooling method, etc. The processing and transporting method of the furnace body 11 can be a continuous type in which the heating and cooling of the workpieces involved in the heat treatment are carried out continuously, or a batch type in which the heating and cooling of the workpieces are carried out intermittently.

[0012] The furnace body 11 may be equipped with a conveying device 111 for conveying the workpieces within the furnace and for loading and unloading the workpieces into and out of the furnace (see FIGS. 1 and 2). The conveying device 111 is not particularly limited in terms of its configuration, etc., as long as it is capable of conveying the workpieces. Specifically, the conveying device 111 may be a belt conveyor, a roller conveyor, or the like. The furnace body 11 has an inlet 112 for inserting the object to be treated into the furnace and an outlet 113 for removing the object to be treated from the furnace (see FIGS. 1 and 2). Within the furnace body 11, the object to be treated is transported by a transport device 111 with the inlet 112 side being the upstream side and the outlet 113 side being the downstream side, and the direction from the upstream side to the downstream side being the transport direction.

[0013] The interior of the furnace body 11 may be a single chamber, or may be divided into multiple chambers. When the interior of the furnace body 11 is divided into multiple chambers, a heating chamber 115 for heating the workpiece and a cooling chamber 116 for cooling the workpiece can be provided. The heating chamber 115 and the cooling chamber 116 are arranged such that the heating chamber 115 is located upstream and the cooling chamber 116 is located downstream in the direction in which the workpiece is transported inside the furnace (see FIGS. 1 and 2). The heating chamber 115 and the cooling chamber 116 are not particularly limited in terms of their internal configuration, structure, etc., and may be configured according to their respective purposes.

[0014] For example, the heating chamber 115 may be provided with a temperature raising device 119 for raising the temperature inside the heating chamber 115 in order to heat the object to be treated. The temperature raising device 119 may be a heater that raises the temperature inside the heating chamber 115 by heat exchange, or a burner that raises the temperature inside the heating chamber 115 by injecting combustion gas, but a heater is more useful from the viewpoint of decarbonization. The cooling chamber 116 may be provided with a temperature lowering device that lowers the temperature inside the cooling chamber or a cooling device that cools the workpiece for the purpose of cooling the workpiece. The temperature lowering device or cooling device may be one that indirectly cools the workpiece by heat exchange or the like, or one that directly cools the workpiece by applying cold air or the like, and specific examples include a blower fan, a stirring fan, and a cooler. The cooling chamber 116 may also be further divided into two or more chambers depending on the purpose, for example, to cool the workpiece in stages.

[0015] When a heating chamber 115 and a cooling chamber 116 are provided inside the furnace body 11, a front chamber 117 can be provided upstream of the heating chamber 115 in the direction of transport of the workpiece inside the furnace body 11, and a rear chamber 118 can be provided downstream of the cooling chamber 116 (see Figures 1 and 2). The anterior chamber 117 is a chamber for inserting the workpiece into the furnace, and prevents the heating chamber 115 from directly connecting with the outside of the furnace during insertion, thereby preventing outside air from flowing into the heating chamber 115. Of the multiple chambers provided inside the furnace body 11, the anterior chamber 117 is arranged at the most upstream side in the direction in which the workpiece is transported. For this reason, the inlet 112 described above can be provided in this anterior chamber 117 so as to open toward the outside of the furnace. The rear chamber 118 is a chamber for removing the workpiece from the furnace, and prevents outside air from flowing into the cooling chamber 116 inside the furnace when the workpiece is being removed. Of the multiple chambers provided inside the furnace body 11, the rear chamber 118 is arranged on the most downstream side in the direction in which the workpiece is transported. For this reason, the above-mentioned outlet 113 can be provided in this rear chamber 118 so as to open toward the outside of the furnace.

[0016] When the furnace body 11 has a heating chamber 115 and a cooling chamber 116 inside the furnace, an opening 114 for transporting the workpiece can be provided between the heating chamber 115 and the cooling chamber 116 (see FIGS. 1 and 2). Furthermore, when the furnace body 11 includes the front chamber 117 and the rear chamber 118, openings 114 can be provided between the front chamber 117 and the heating chamber 115, and between the cooling chamber 116 and the rear chamber 118, respectively. The heating chamber 115 and cooling chamber 116 in the furnace, as well as the front chamber 117 and rear chamber 118, can be connected to each other through openings 114 provided between adjacent chambers. Furnace body 11 may also be configured to include doors (not shown) for opening and closing entrance 112, exit 113 and / or opening 114.

[0017] (2) Gas supply system (2-1) Hydrogen gas supply system The hydrogen gas supply system 12 is for supplying hydrogen (H2) gas as atmospheric gas into the furnace of the furnace body 11 (see FIGS. 1 and 2). The hydrogen gas supply system 12 extends from a hydrogen tank 121 that stores hydrogen (H 2 ) gas and is connected to the furnace body 11 .

[0018] A first adjusting valve 122 can be connected to the hydrogen gas supply system 12. This first adjusting valve 122 makes it possible to adjust the amount of hydrogen (H2) gas supplied by the hydrogen gas supply system 12 to the inside of the furnace body 11, and can adjust the supply amount from 0 (m 3 / h), the supply of hydrogen (H2) gas can be stopped. The type of valve element used for the first adjusting valve 122 is not particularly limited, but an electric valve, a solenoid valve, or the like can be used. The supply amount of hydrogen (H2) gas can be adjusted appropriately depending on the heat treatment to be performed on the workpiece, and is not particularly limited.

[0019] The hydrogen gas supply system 12 can be connected to any location in the furnace body 11, but if the furnace body 11 has a heating chamber 115 and a cooling chamber 116 inside the furnace, it can be connected to the heating chamber 115 (see Figures 1 and 2). When the hydrogen gas supply system 12 is connected to the heating chamber 115, hydrogen (H2) gas can be supplied to the heating chamber 115. As described above, the heating chamber 115 and the cooling chamber 116 are internally connected via the opening 114. Therefore, the cooling chamber 116 can be configured such that hydrogen (H2) gas, which is the atmospheric gas, is diverted from the heating chamber 115 via the opening 114.

[0020] When the furnace body 11 includes a front chamber 117, the front chamber 117 and the heating chamber 115 are in communication with each other through the opening 114. Therefore, the front chamber 117 can be configured to divert hydrogen (H2) gas, which is atmospheric gas, from the heating chamber 115 through the opening 114. When the furnace interior of the furnace body 11 includes a rear chamber 118, the rear chamber 118 and the cooling chamber 116 are internally connected via the opening 114. Therefore, the rear chamber 118 can be configured to divert hydrogen (H2) gas, which is atmospheric gas, from the cooling chamber 116 via the opening 114. The hydrogen (H2) gas diverted from the cooling chamber 116 to the rear chamber 118 was originally diverted from the heating chamber 115 to the cooling chamber 116.

[0021] That is, when the hydrogen gas supply system 12 is connected to the heating chamber 115, hydrogen (H2) gas is first supplied to the heating chamber 115 and can be diverted from the heating chamber 115 to the cooling chamber 116, front chamber 117, and rear chamber 118. In this way, when hydrogen (H2) gas is supplied to the heating chamber 115 and then diverted from the heating chamber 115 to each chamber, the amount of hydrogen (H2) gas used can be reduced compared to a configuration in which hydrogen (H2) gas is supplied to each chamber.

[0022] (2-2) Nitrogen gas supply system The nitrogen gas supply system 13 is for supplying nitrogen (N2) gas into the furnace body 11 as atmospheric gas. The nitrogen gas supply system 13 extends from a nitrogen tank 131 that stores nitrogen (N 2 ) gas and is connected to the furnace body 11. A PSA nitrogen gas production apparatus 16 (hereinafter also abbreviated as "PSA apparatus 16") can be connected to the nitrogen tank 131. In other words, the PSA apparatus 16 is connected to the nitrogen gas supply system 13 via the nitrogen tank 131.

[0023] The PSA unit 16 is a unit that produces nitrogen (N2) gas, and the produced nitrogen (N2) gas can be sent to a nitrogen tank 131 and stored in the nitrogen tank 131. A flow rate adjustment valve 132 can be connected between the nitrogen tank 131 and the PSA unit 16. The PSA unit 16 and the flow rate adjustment valve 132 will be described later. When the PSA device 16 is connected to the nitrogen gas supply system 13, a pressure reducing valve 133 can be connected to the nitrogen gas supply system 13. Specifically, the pressure reducing valve 133 is connected to the nitrogen gas supply system 13 between the nitrogen tank 131 and the furnace body 11. Since the nitrogen (N2) gas produced by the PSA device 16 is in a high-pressure state, the pressure reducing valve 133 is provided to reduce the pressure of the nitrogen (N2) gas when it is supplied into the furnace body 11.

[0024] When the furnace body 11 has a heating chamber 115 and a cooling chamber 116 inside, the nitrogen gas supply system 13 can be connected to the heating chamber 115 in the same manner as the hydrogen gas supply system 12 described above (see FIGS. 1 and 2). When the nitrogen gas supply system 13 is connected to the heating chamber 115, nitrogen (N2) gas can be supplied to the heating chamber 115. That is, the heating chamber 115 and the cooling chamber 116 are connected to each other internally, and when the nitrogen gas supply system 13 is connected to the heating chamber 115, the cooling chamber 116 can be configured to divert nitrogen (N2) gas, which is the atmospheric gas, from the heating chamber 115, similar to the hydrogen gas supply system 12 described above. If the furnace interior of the furnace body 11 is equipped with a front chamber 117 and a rear chamber 118, nitrogen (N2) gas can be diverted from the heating chamber 115 to the front chamber 117 and from the cooling chamber 116 to the rear chamber 118, similar to the hydrogen gas supply system 12 described above.

[0025] (2-3) PSA nitrogen gas production equipment The PSA nitrogen gas production device 16 removes oxygen (O2) from the air to produce nitrogen (N2) gas (see FIG. 1). Specifically, the PSA unit 16 includes an air supplier 161 and an adsorption vessel 162 connected to the air supplier 161 . The air supplier 161 may be, for example, a compressor, an air tank, or the like, and can supply air to the adsorption tank 162 in a high-pressure state. The adsorption tank 162 is filled with an adsorbent that adsorbs and removes gases other than nitrogen (N2) from the air (specifically, mainly oxygen (O2), but also moisture (H2O), carbon dioxide (CO2), carbon monoxide (CO), etc.). The PSA device 16 can produce nitrogen (N2) gas by passing air supplied at high pressure through the adsorption tank 162 inside the device and adsorbing and removing gases other than nitrogen (N2), particularly oxygen (O2), from the air.

[0026] The PSA unit 16 may include multiple adsorption vessels 162 . When the PSA device 16 has multiple adsorption tanks 162, the adsorption tanks 162 can be connected to each other via multiple switching valves 163, allowing them to be appropriately switched between performing adsorption removal of oxygen (O2) and the like and pausing adsorption removal. In other words, when the PSA unit 16 has multiple adsorption tanks 162, by switching to one adsorption tank 162 before the adsorption capacity in one adsorption tank 162 becomes full, it is possible to continuously perform adsorption removal of oxygen (O2) and the like. In addition, the adsorption tank 162 can also perform a regeneration process for the adsorbent when adsorption removal is suspended.

[0027] The adsorbent filled in the adsorption tank 162 can be any material as long as it can adsorb oxygen (O2). Activated carbon, zeolite, silica gel, and activated alumina can be used as the adsorbent. Activated carbon, zeolite, silica gel, and activated alumina are all granular porous materials with numerous pores, and their adsorption performance can be changed depending on the composition ratio, pore size (average pore diameter), total pore volume, specific surface area, pore distribution, etc. In other words, the adsorbent can be used with its composition ratio, pore size (average pore diameter), total pore volume, specific surface area, pore distribution, etc. adjusted or regulated depending on the oxygen (O2) to be adsorbed.

[0028] The activated carbon may include a molecular sieve carbon. The molecular sieve carbon is obtained by activating a carbonized material with numerous pores, such as charcoal, coal, coke, coconut shell, synthetic resin, or pitch. In this activation treatment, the pore size can be adjusted depending on the treatment temperature, amount of activation gas, and treatment time. That is, the pore size of the carbon molecular sieve is adjusted to correspond to the size of the oxygen (O2) molecule, so that the carbon molecular sieve can adsorb oxygen (O2). Note that the pore size of the carbon molecular sieve capable of adsorbing oxygen (O2) is adjusted to about 3 to 5 angstroms. Furthermore, by reducing the pressure in the adsorption vessel 162, the adsorbed oxygen (O2) can be suitably desorbed from the molecular sieve carbon, allowing it to be regenerated.

[0029] In the PSA device 16, a flow rate adjustment valve 132 can be connected between the nitrogen (N 2 ) gas output part, specifically, the nitrogen tank 131. The flow rate adjusting valve 132 can be an electromagnetic valve or the like, and the flow rate of nitrogen (N2) gas from the PSA device 16 to the nitrogen gas supply system 13 can be changed arbitrarily by controlling the opening degree.

[0030] The PSA device 16 can change the purity of the nitrogen (N2) gas produced by changing the flow rate of the nitrogen (N2) gas using the flow rate adjustment valve 132. In other words, when the flow rate of nitrogen (N2) gas is reduced by the flow control valve 132, the time during which the air is adsorbed in the adsorption tank 162 in the PSA unit 16 (or the time during which the air remains in the adsorption tank 162) becomes longer, and the amount of oxygen (O2) adsorbed and removed from the air increases accordingly. On the other hand, if the flow rate of nitrogen (N2) gas is increased by the flow control valve 132, the time during which air is adsorbed in the adsorption tank 162 in the PSA unit 16 (or the time during which air remains in the adsorption tank 162) becomes shorter, and the amount of oxygen (O2) adsorbed and removed from the air decreases accordingly.

[0031] Regarding the purity of nitrogen (N2) gas, air normally contains approximately 78% nitrogen (N2) and approximately 21% oxygen (O2), and approximately 99% of air is nitrogen (N2) and oxygen (O2). Therefore, if the amount of oxygen (O2) adsorbed and removed from air increases, the purity of nitrogen (N2) gas increases, and if the amount of oxygen (O2) adsorbed and removed from air decreases, the purity of nitrogen (N2) gas decreases. The nitrogen (N2) gas produced by the PSA unit 16 mainly contains oxygen (O2) as an impurity. Therefore, when the purity of the nitrogen (N2) gas is adjusted using the PSA unit 16 and the flow rate control valve 132, the amount of oxygen (O2) supplied to the furnace body 11 can be increased or decreased depending on the purity, thereby enabling adjustment of the amount of oxygen (O2) supplied.

[0032] As a reference example, a PSA device (manufactured by Kuraray, trade name "Kurasep") was actually used to measure the flow rate (m 3 The change in purity (%) of nitrogen (N2) gas when the flow rate ( / h) was appropriately changed is shown in Table 1 below. In Table 1, "No. 1" to "No. 4" are PSA devices manufactured by the same company and have the same name, but each device has a different model (No. 1: model "MR-22", No. 2: model "MR-30", No. 3: model "MR-37", No. 4: model "MR-55"). From the results shown in Table 1, the PSA device can be used with a nitrogen (N2) gas flow rate (m 3 It can be seen that the purity (%) of nitrogen (N2) gas can be changed depending on the temperature (°C / h).

[0033] [Table 1]

[0034] (3) Dew point meter A dew point meter 17 for measuring the dew point temperature (°C) inside the furnace is attached to the heating chamber 111 of the furnace body 11. The dew point meter 17 is electrically connected to the controller 18 . The controller 18 can obtain the dew point temperature inside the furnace measured by the dew point meter 17 and use it to control the dew point. In addition to the dew point meter, the furnace body 11 may be equipped with measuring instruments for measuring the hydrogen concentration, oxygen concentration, and furnace temperature inside the furnace.

[0035] (4) Controller The controller 18 controls the dew point temperature, which is the object of control. The controller 18 is electrically connected to the flow rate control valve 132, and by operating the flow rate control valve 132, the flow rate of the nitrogen (N2) gas from the PSA device 16 to the nitrogen gas supply system 13 can be adjusted. By adjusting the flow rate of the nitrogen (N2) gas, the controller 18 can adjust the purity of the nitrogen (N2) gas produced, and can increase or decrease the amount of oxygen that is mixed with the nitrogen (N2) gas and sent into the furnace of the furnace body 11. The atmospheric furnace 10 utilizes the fact that moisture (H2O) is generated in the atmosphere due to the reaction between oxygen (O2) in the furnace and hydrogen (H2) gas supplied as atmospheric gas, and can control the dew point by increasing or decreasing the amount of oxygen to control the amount of moisture (H2O) generated. Furthermore, the atmosphere furnace 10 can control the amount of oxygen sent into the furnace, which is adjusted by the controller 18, to create an atmosphere inside the furnace that prevents oxidation of the workpiece (hereinafter referred to as a "non-oxidizing atmosphere" or "non-oxidizing" for short).

[0036] (4-1) Control target In the atmosphere furnace (first embodiment) of the present invention, the dew point temperature is controlled by the controller 18. To control the dew point temperature, the controller 18 adjusts the purity of the nitrogen gas produced by the PSA nitrogen gas production device 16, increases or decreases the amount of oxygen mixed with the nitrogen gas and sent into the furnace body 10, and increases or decreases the amount of moisture generated in the atmosphere inside the furnace by the reaction between the oxygen and hydrogen gas. Specifically, the controller 18 operates the flow control valve 132 connected to the PSA device 16, and controls the amount of moisture (H2O) in the atmosphere inside the furnace by adjusting the purity of the nitrogen (N2) gas by adjusting the flow rate of the nitrogen (N2) gas, thereby controlling the dew point. Furthermore, the controller 18 can be electrically connected to a valve (valve) capable of adjusting the supply amount of hydrogen (H2) gas, such as the first adjusting valve 122 or a valve other than the first adjusting valve 122, in the hydrogen gas supply system 12. In this case, the concentration (vol%) of hydrogen (H2) gas in the atmosphere inside the furnace can be adjusted to control the amount of moisture (H2O) in the atmosphere inside the furnace.

[0037] The reason why the atmospheric furnace (first form) of the present invention controls the dew point temperature is that, while ordinary atmospheric furnaces use petroleum-based gases called DX gas, RX gas, etc. as the atmospheric gas, nitrogen gas and hydrogen gas are used as the atmospheric gas in order to achieve decarbonization (carbon neutrality). That is, regarding heat treatment, for example, brazing treatment, an atmosphere in a furnace with a dew point of about 5° C. to 40° C. This is because the affinity between the molten brazing filler metal and the base material is important for the molten brazing filler metal to flow and spread over the surface of the base material (diffusion) without being repelled by the surface of the base material, and for the molten brazing filler metal to penetrate into gaps between the base materials by capillary action (penetration). More specifically, three tensions act between the molten brazing filler metal and the base metal: the surface tension of the base metal, the interfacial tension between the molten brazing filler metal and the base metal, and the surface tension of the molten brazing filler metal. The affinity (or "wettability") of the molten brazing filler metal to the base metal is determined by the balance of these three tensions, and in order to impart this affinity (or "wettability"), it is necessary to create an atmosphere in the furnace with an appropriate dew point during the brazing process.

[0038] In the case of a typical atmosphere furnace, the atmosphere gas using petroleum-based gas has a dew point of approximately 5°C to 30°C (however, this is the dew point at the temperature in the cooled state after the transformation reaction), as the petroleum-based gas contains moisture, and therefore essentially meets the moderate dew point conditions required for brazing processing. In the case of the atmospheric furnace of the present invention, the atmospheric gas using nitrogen gas and hydrogen gas has a dew point of about -60°C to -10°C, which does not satisfy the appropriate dew point required for brazing treatment. Therefore, when the atmospheric furnace 10 using nitrogen gas and hydrogen gas as atmospheric gases is used for the brazing process, it is necessary to control the dew point so that the atmosphere inside the furnace has an appropriate dew point.

[0039] In brazing, it is important to adjust the amount of oxygen supplied to the furnace to prevent oxidation of the workpiece. In particular, since the degree of susceptibility to oxidation of the workpiece varies depending on the material of the base metal (the type of metal used in the material), it is necessary to adjust the amount of oxygen taking into account the susceptibility to oxidation. For example, when the base material is made of iron, its oxidation proceeds according to the following reaction formulas (1) and (2). Fe+1 / 2O2 → FeO (1) 3FeO+1 / 2O2 → Fe3O4 (2) When the base material is copper-based, its oxidation proceeds according to the following reaction formula (3). Cu+1 / 2O2→ CuO (3) When the base material is iron-based, its oxidation proceeds through two reaction systems, the above reaction formulas (1) and (2). In contrast, when the base material is copper-based, its oxidation proceeds through one reaction system, the above reaction formula (3). For this reason, iron-based materials are more susceptible to oxidation than copper-based materials, and it is desirable to adjust the amount of oxygen taking this into consideration.

[0040] Regarding the oxygen (O2) in the atmosphere inside the furnace, this oxygen (O2) reacts with hydrogen (H2) gas supplied as atmospheric gas to generate moisture (H2O) according to the following reaction formula (4). H2+1 / 2O2→ H2O (4) During brazing, hydrogen (H2) gas used as the atmospheric gas can remove oxygen (O2) from the atmosphere by promoting the above reaction (4). As a result of removing oxygen (O2) from the atmosphere, the oxidation reactions shown in reaction (1), (2), or (3) are prevented from proceeding, thereby preventing oxidation in the furnace. In addition, in a configuration in which the above-described hydrogen gas supply system 12 is connected to the heating chamber 115, the above reaction formula (4) can be favorably promoted by utilizing the high-temperature environment in which the workpiece is heated for heat treatment in the heating chamber 115. That is, in the case of the atmospheric furnace (first embodiment) of the present invention, in which moisture (H2O) is generated by the reaction of hydrogen (H2) gas with oxygen (O2) and the dew point is controlled by the moisture (H2O), it is preferable that the hydrogen gas supply system 12 be connected to the heating chamber 115 in order to favorably promote the reaction formula (4).

[0041] The atmospheric furnace (first embodiment) of the present invention generates moisture (HO) through the progression of the above reaction formula (4), and increases the concentration (vol%) of moisture (HO) in the furnace, thereby increasing the dew point in the furnace. Reaction formula (4) is an equilibrium reaction, and a reverse reaction may occur depending on the concentrations (vol%) of hydrogen (H2) gas, oxygen (O2), and moisture (H2O) in the atmosphere. However, although the equilibrium constant of reaction formula (4) reaches a value of about 1 at about 3727°C (4000K), brazing is usually carried out at a furnace temperature of about 600°C to 1120°C. In other words, at a heat treatment temperature of about 1120°C or less for the workpiece, reaction formula (4) is unlikely to cause a reverse reaction and proceeds as a forward reaction even if the concentration (vol%) of water (H2O) in the furnace increases.

[0042] As described above, the PSA device 16 produces nitrogen (N2) gas at a flow rate (m 3 The purity (%) can be adjusted according to the rate (hours / hour), and by adjusting the purity (%), the amount of oxygen (O2) supplied to the furnace together with nitrogen (N2) gas can be adjusted. When the atmospheric furnace (first embodiment) of the present invention is used for brazing processing, the amount of oxygen (O2) supplied to the furnace can be adjusted by adjusting the purity (%) of the nitrogen (N2) gas produced by the PSA device 16. By controlling the progress of reaction equation (4) by adjusting the amount of hydrogen (H2) gas supplied, the moisture content (vol%) in the atmosphere inside the furnace can be adjusted, and control of the dew point can be achieved.

[0043] For example, if the base material is iron-based, it is more susceptible to oxidation than copper-based materials. To prevent this oxidation, the furnace must be kept in an atmosphere in which the above reaction formula (4) proceeds. Regarding reaction equation (4), the equilibrium equation for chemical equilibrium in the gas phase is expressed as follows: the equilibrium constant is K and the partial pressure of water is P H2O , hydrogen partial pressure P H2 , oxygen partial pressure P O2 This can be expressed by the following equation (4-1). K = (P H2O ) 2 / 〔(P H2 ) 2 ×P O2 ) (4-1) By converting the above equation (4-1), we obtain the following equation (4-2). (K×P O2 ) (1 / 2) = P H2O / P H2 (4-2) In equation (4-2), K is a constant, so the oxygen partial pressure (P O2 ) is the hydrogen partial pressure (P H2 ) relative to the partial pressure of water (P H2O ) ratio (P H2O / P H2 ) is determined according to this ratio (P H2O / P H2 ) for the hydrogen partial pressure (P H2 ) can be easily adjusted by adjusting the amount of hydrogen (H2) gas supplied to the furnace. Therefore, reaction equation (4) is based on the partial pressure of hydrogen in the atmosphere (P H2Specifically, the concentration (vol%) of hydrogen gas in the atmosphere is increased by adjusting the amount of hydrogen (H2) gas supplied to the furnace, and the oxygen partial pressure (P O2 ) (increasing the reducing properties of the atmosphere) Regarding the hydrogen gas concentration (vol%), for example, if the base material is iron-based, the range of oxygen partial pressure (atm) in the atmosphere related to the progress of the oxidation reaction can be calculated from the equilibrium constants of reaction formulas (1) and (2). Based on these calculated values, the hydrogen gas concentration (vol%) or the range of hydrogen partial pressure (atm) in the atmosphere that does not allow reaction formulas (1) and (2) to progress can be calculated and set in advance.

[0044] The treatment temperature for heat treatment is also important for controlling the progress of the above reactions (1) to (4), because the equilibrium constants of the oxidation reactions (1) to (3) and the moisture-producing reaction (4) vary depending on the treatment temperature. The treatment temperature is, for example, 1050°C to 1120°C for copper brazing, 720°C to 920°C for phosphor bronze brazing, 870°C to 1120°C for nickel brazing, 620°C to 840°C for silver brazing, and 1000°C to 1120°C for brass brazing. As for heat treatments other than brazing, for example, bright annealing of stainless steel is performed at 1000°C to 1120°C, and non-oxidizing annealing of iron-based materials is performed at 650°C to 920°C. The atmospheric furnace (first embodiment) of the present invention can be used for heat treatments such as the above-mentioned brazing, bright annealing, and oxidation-free annealing.

[0045] (4-2) Dew point control The controller 18 stores a set value for the dew point temperature in advance and also has a program related to dew point control stored therein, and can perform dew point control based on the measured dew point value obtained from the dew point meter 17 so that the measured value falls within the set value range. FIG. 3 is a flowchart showing a specific example of dew point control. In the dew point control, first, the dew point temperature is measured in the atmosphere furnace, and the measured value is obtained (step S11). Next, it is determined whether the measured dew point temperature is within a set range (step S12). If the dew point temperature is within the set range (step S12; Yes), the flow rate from the PSA device 16 is maintained as it is, the purity of the N2 gas is maintained, and the operation is terminated.

[0046] If the dew-point temperature is outside the set range (step S12; No), it is determined whether the dew-point temperature falls below the set range (whether the dew-point temperature falls below the lower limit of the set value) (step S13). If the dew-point temperature is below the lower limit of the set value and does not fall within the set range (step S13; Yes), the flow control valve 132 is operated to open, and the flow rate from the PSA device 16 to the nitrogen gas supply system 13 is increased (step S14). As a result, the purity of the N2 gas decreases (step S15A), the amount of O2 supplied to the furnace increases, and the dew-point temperature rises (step S15B).

[0047] On the other hand, if the dew-point temperature is not within the set range (step S12; No) and the dew-point temperature is not below the set range (step S13; No), it is determined that the dew-point temperature exceeds the set range (the dew-point temperature exceeds the upper limit of the set value) (step S16). If the dew-point temperature exceeds the upper limit of the set value and exceeds the set range (step S16), the flow control valve 132 is closed to reduce the flow rate from the PSA device 16 to the nitrogen gas supply system 13 (step S17). This increases the purity of the N2 gas (step S18A), reduces the amount of O2 supplied to the furnace, and lowers the dew-point temperature (step S18B).

[0048] After the dew-point temperature is increased or decreased (S15B, S18B), the dew-point temperature is measured again (step S11), and it is determined whether the dew-point temperature is within the set range (step S12). If the reacquired dew-point temperature is within the set range (step S12; Yes), the operation is terminated. If the reacquired dew-point temperature is not within the set range (step S12; No), the purity of the N2 gas is repeatedly adjusted (S15A, S18A) by adjusting the flow rate from the PSA device 16 (S14, S17) until the dew-point temperature is within the set range.

[0049] (5) Gas exhaust system The atmosphere furnace 10 may further include a first gas exhaust system 21 connected to the inlet 112 end of the furnace body 11 to exhaust gas from the furnace, a first exhaust valve 22 connected to the first gas exhaust system 21 to adjust the exhaust rate, a second gas exhaust system 23 connected to the outlet 113 end to exhaust gas from the furnace, and a second exhaust valve 24 connected to the second gas exhaust system 23 to adjust the exhaust rate (see Figures 1 and 2). The first exhaust valve 22 and the second exhaust valve 24 may be electric valves, electromagnetic valves, or the like, and may be electrically connected to the controller 18. The controller 18 adjusts the exhaust volume by operating the first exhaust valve 22 and the second exhaust valve 24 for at least one of the first gas exhaust system 21 and the second gas exhaust system 23, and can control the amount of atmospheric gas diverted from the heating chamber 115 to the inlet 112 end or the outlet 113 end of the furnace body 11.

[0050] Specifically, the first gas exhaust system 21 can be connected to the vicinity of the inlet 112 in the front chamber 117 arranged at the end of the furnace body 11 on the inlet 112 side. When the first exhaust valve 22 is operated by the controller 18 and exhaust is performed from the first gas exhaust system 21 to the outside of the furnace, the exhaust creates a flow of atmospheric gas inside the furnace body 11 from the heating chamber 115 to the front chamber 117 (the end on the inlet 112 side) (see the arrows inside the furnace in Figures 1 and 2).

[0051] The second gas exhaust system 23 can be connected to the rear chamber 118 disposed at the end of the furnace body 11 on the outlet 113 side, near the outlet 113 . When the second exhaust valve 24 is operated by the controller 18 and exhaust is performed from the second gas exhaust system 23 to the outside of the furnace, a flow of atmospheric gas can be formed within the furnace body 11 from the heating chamber 115 through the cooling chamber 116 to the rear chamber 118 (the end on the outlet 113 side) in conjunction with the exhaust (see the arrows inside the furnace in Figures 1 and 2).

[0052] When the hydrogen gas supply system 12 and the nitrogen gas supply system 13 are connected to the heating chamber 115, the atmospheric gases, hydrogen gas and nitrogen gas, are supplied to the heating chamber 115 and then diverted from the heating chamber 115 to each of the front chamber 117, the cooling chamber 116, and the rear chamber 118. By exhausting gas outside the furnace, the first gas exhaust system 21 and the second gas exhaust system 23 can create a flow of atmospheric gas inside the furnace from the heating chamber 115 toward the end on the inlet 112 side, and a flow of atmospheric gas from the heating chamber 115 toward the end on the outlet 113 side.

[0053] That is, the first gas exhaust system 21 and the second gas exhaust system 23 form a flow of the atmospheric gas inside the furnace, thereby enabling the atmospheric gas to be suitably diverted from the heating chamber 115 to each chamber. Furthermore, the atmospheric gases, hydrogen gas and nitrogen gas, and moisture (water vapor) generated by the reaction of the hydrogen gas with oxygen in the furnace are diffused approximately uniformly when they are diverted from the heating chamber 115 to each chamber according to the flows formed by the first gas exhaust system 21 and the second gas exhaust system 23. This diffusion can prevent the concentrations of the atmospheric gases, etc., from becoming uneven in the furnace.

[0054] Within the furnace body 11, the amount of gas diverted from the heating chamber 115 toward the end on the inlet 112 side and the amount of gas diverted from the heating chamber 115 toward the end on the outlet 113 side can be controlled by adjusting the exhaust amounts of the first gas exhaust system 21 and the second gas exhaust system 23 by operating the first exhaust valve 22 and the second exhaust valve 24. That is, when the first exhaust valve 22 is opened wider than the second exhaust valve 24 and the exhaust volume of the first gas exhaust system 21 is made larger than the exhaust volume of the second gas exhaust system 23, the amount of gas diverted from the heating chamber 115 toward the end on the inlet 112 side is greater than the amount toward the end on the outlet 113 side. When inserting the workpiece into the front chamber 117 of the furnace body 11, by controlling the amount of gas diverted from the heating chamber 115 toward the end of the inlet 112 so that it is increased, it is possible to suppress the inflow of outside air (air) into the furnace from the inlet 112, or to quickly exhaust the outside air (air) that has flowed into the furnace from the inlet 112 through the first gas exhaust system 21.

[0055] Furthermore, when the second exhaust valve 24 is opened wider than the first exhaust valve 22 and the exhaust volume of the second gas exhaust system 23 is made larger than the exhaust volume of the first gas exhaust system 21, the amount of gas diverted from the heating chamber 115 toward the end on the outlet 113 side is greater than the amount toward the end on the inlet 112 side. When the workpiece is removed from the rear chamber 118 of the furnace body 11, by controlling the amount of gas diverted from the heating chamber 115 toward the end on the outlet 113 side to be increased, it is possible to suppress the inflow of outside air (air) into the furnace from the outlet 113, or to quickly exhaust the outside air (air) that has flowed into the furnace from the outlet 113 through the second gas exhaust system 23.

[0056] [2] Atmospheric furnace (second form) The atmospheric furnace of the present invention is an atmospheric furnace 10 in which a workpiece is heat-treated in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body 11 that accommodates the object to be treated; a hydrogen gas supply system 12 connected to the furnace body 11; a nitrogen gas supply system 13 connected to the furnace body 11; a moisture supply system 14 connected to the furnace body 11 to supply moisture into the furnace, and a control valve 15 connected to the moisture supply system 14; a dew point meter 17 attached to the furnace body 11 to measure the dew point temperature inside the furnace; a controller (18) that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter (17); The controller 18 controls the dew point temperature by operating the control valve 15 and adjusting the amount of moisture supplied from the moisture supply system 14 in accordance with the dew point temperature obtained from the dew point meter 17 (see FIG. 2). Below, we will explain the configuration of the furnace body 11, hydrogen gas supply system 12, nitrogen gas supply system 13, PSA nitrogen gas production device 16, dew point meter 17, and controller 18 that the second embodiment of the atmosphere furnace 10 is equipped with, but we will focus on the differences from the first embodiment of the atmosphere furnace 10 and omit explanations of similarities.

[0057] (1) Furnace body This is the same as the (1) furnace body of the above-mentioned [1] atmosphere furnace (first embodiment), and therefore a description thereof will be omitted.

[0058] (2) Gas supply system (2-1) Hydrogen gas supply system The gas supply system (2) and the hydrogen gas supply system (2-1) are the same as those in the atmospheric furnace (first embodiment) [1] described above, and therefore the explanation will be omitted.

[0059] (2-2) Nitrogen gas supply system The nitrogen gas supply system 13 is for supplying nitrogen (N2) gas into the furnace body 11 as atmospheric gas. The nitrogen gas supply system 13 extends from a nitrogen tank 131 that stores nitrogen (N 2 ) gas and is connected to the furnace body 11. The nitrogen tank 131 can be connected to the PSA unit 16 (see FIG. 2). When the PSA unit 16 is connected to the nitrogen tank 131, the nitrogen (N2) gas produced by the PSA unit 16 can be stored in the nitrogen tank 131. In addition, a supply valve 132A that allows or restricts the supply of nitrogen (N2) gas from the PSA device 16 to the nitrogen tank 131 can be connected between the nitrogen tank 131 and the PSA device 16. A solenoid valve, an electric valve, or the like can be used for this supply valve 132A. The supply valve 132A and the PSA device 16 may be omitted, in which case the nitrogen tank 131 can store nitrogen (N2) gas that has been produced elsewhere in advance.

[0060] A second adjustment valve 133A can be connected to the nitrogen gas supply system 13. This second adjustment valve 133A makes it possible to adjust the amount of nitrogen (N2) gas supplied by the nitrogen gas supply system 13 to the inside of the furnace body 11. The type of valve element used for the second adjusting valve 133A is not particularly limited, but a solenoid valve, an electric valve, or the like can be used, and when the PSA device 16 is used, a pressure reducing valve can also be used. The amount of nitrogen (N2) gas supplied is not particularly limited and can be adjusted appropriately depending on the atmosphere in the furnace so as to maintain the atmosphere. When the furnace body 11 has a heating chamber 115 and a cooling chamber 116 inside, the nitrogen gas supply system 13 can be connected to the heating chamber 115 (see FIG. 2). In this case, nitrogen (N2) gas is supplied to the heating chamber 115 and can be diverted from the heating chamber 115 to the front chamber 117, the cooling chamber 116, and the rear chamber 118.

[0061] (2-3) PSA nitrogen gas production equipment The configuration is the same as that of (2) gas supply system and (2-3) PSA nitrogen gas production device of the above-mentioned [1] atmospheric furnace (first embodiment), and therefore a description of the configuration will be omitted. When using the PSA device 16, the second form of the atmospheric furnace 10 can be used without adjusting the purity of the nitrogen (N2) gas by adjusting the flow rate, and the purity can be maintained at a high purity such as 99.999% by keeping the flow rate at a constant value.

[0062] (2-4) Moisture supply system The moisture supply system 14 is for supplying moisture (H2O) into the furnace of the furnace body 11 (see FIG. 2). The moisture supply system 14 extends from a humidifier 141 that generates moisture (water vapor) and is connected to the furnace body 11.

[0063] A control valve 15 is connected to the moisture supply system 14. This control valve 15 makes it possible to adjust the amount of moisture (H2O) supplied by the moisture supply system 14 to the inside of the furnace body 11, and can adjust the supply amount from 0 (m 3 / h), the supply of water (H2O) can be stopped. The type of valve element used for the control valve 15 is not particularly limited, but an electric valve, a solenoid valve, or the like can be used. The control valve 15 is electrically connected to a controller 18, and by operating the controller 18, the amount of moisture (H2O) supplied can be adjusted appropriately according to the dew point temperature inside the furnace.

[0064] The moisture supply system 14 can be connected to any location in the furnace body 11, but when the furnace body 11 has a heating chamber 115 and a cooling chamber 116 inside the furnace, it can be connected to the heating chamber 115 (see FIG. 2). When the moisture supply system 14 is connected to the heating chamber 115, moisture (H2O) can be supplied to the heating chamber 115. The heating chamber 115 and the cooling chamber 116 are in communication with each other through the opening 114. Therefore, the cooling chamber 116 can be configured to divert moisture (H2O) from the heating chamber 115 through the opening 114.

[0065] When the furnace body 11 includes a front chamber 117, the front chamber 117 and the heating chamber 115 are in communication with each other through the opening 114. Therefore, the front chamber 117 can be configured to divert moisture (H2O) from the heating chamber 115 through the opening 114. When the furnace interior of the furnace body 11 includes a rear chamber 118, the rear chamber 118 and the cooling chamber 116 are in communication with each other through the opening 114. Therefore, the rear chamber 118 can be configured to divert moisture (H2O) from the cooling chamber 116 through the opening 114. The moisture (H2O) diverted from the cooling chamber 116 to the rear chamber 118 was originally diverted from the heating chamber 115 to the cooling chamber 116. That is, when the moisture supply system 14 is connected to the heating chamber 115, moisture (H2O) is first supplied to the heating chamber 115 and can be diverted from the heating chamber 115 to the cooling chamber 116, front chamber 117, and rear chamber 118. In this way, when moisture (H2O) is supplied to the heating chamber 115 and diverted from the heating chamber 115 to each chamber, it is possible to prevent the moisture concentration in the furnace from becoming unbalanced and the dew point temperature of the heating chamber 115 from rising excessively, compared to a configuration in which moisture (H2O) is supplied to each chamber.

[0066] (3) Dew point meter This is the same as the (3) dew point meter in the above-mentioned [1] atmosphere furnace (first embodiment), and therefore a description thereof will be omitted.

[0067] (4) Controller The controller 18 controls the dew point temperature, which is the object of control. The controller 18 is electrically connected to a control valve 15 connected to the moisture supply system 14, and by operating the control valve 15 and adjusting the amount of moisture supplied to the furnace body 11, the dew point temperature can be controlled. The atmospheric furnace 10 uses hydrogen (H2) gas as the atmospheric gas, and the atmosphere inside the furnace can be made non-oxidizing by removing oxygen (O2) remaining in the furnace through a reaction with hydrogen (H2). The moisture (H2O) produced by the reaction of this hydrogen (H2) gas with oxygen (O2) can be used to raise the dew point temperature inside the furnace.

[0068] (4-1) Control target In the atmosphere furnace (second embodiment) of the present invention, the control target of the controller 18 is the dew point temperature, similarly to the above-mentioned atmosphere furnace (first embodiment). In this atmosphere furnace (second embodiment), the controller 18 operates the control valve 15 in accordance with the dew point temperature acquired from the dew point meter 17 to adjust the amount of moisture supplied from the moisture supply system 14 in order to control the dew point temperature. The controlled object of the atmosphere furnace (second embodiment) of the present invention will be described below, focusing on the differences from the (4-1) controlled object of the atmosphere furnace (first embodiment) [1] described above.

[0069] In the atmospheric furnace (second embodiment) of the present invention, hydrogen (H2) gas is used mainly to create a reducing atmosphere in the furnace and remove oxygen (O2) from the atmosphere. In other words, in the atmospheric furnace (second embodiment) of the present invention, hydrogen (H2) gas is not used mainly to adjust the moisture content (vol%) in the atmosphere in the furnace. That is, hydrogen (H2) gas supplied as atmospheric gas can remove oxygen (O2) from the atmosphere by reacting with oxygen (O2) in the atmosphere according to the following reaction formula (4). H2+1 / 2O2→ H2O (4) As the reaction (4) proceeds, oxygen (O2) in the atmosphere is removed, and as a result, the oxidation reactions such as the oxidation reactions (1) to (3) described above are hindered from proceeding, thereby preventing oxidation in the furnace. Furthermore, the moisture (H2O) generated by the progress of reaction formula (4) is diffused into the furnace and can be secondarily used to control the dew point of the atmosphere in the furnace.

[0070] Reaction formula (4) is an equilibrium reaction, and a reverse reaction may occur depending on the concentrations (vol%) of hydrogen (H2) gas, oxygen (O2), and moisture (H2O) in the atmosphere. As described above, reaction formula (4) is a reaction whose equilibrium constant is approximately 1 at approximately 3727°C (4000K). Therefore, even if the moisture (HO) concentration (vol%) in the furnace increases at a heat treatment temperature of approximately 1120°C or less for the workpiece, the reverse reaction is unlikely to occur and the reaction proceeds as a forward reaction. As described above, reaction formula (4) increases the supply of hydrogen (H2) gas and the hydrogen partial pressure (P H2 ), that is, increase the reducing property of the atmosphere (oxygen partial pressure (P O2 ) can also be used to suppress the reverse reaction, since the forward reaction proceeds by lowering the

[0071] Therefore, the atmosphere furnace (second embodiment) of the present invention is configured to control the dew point by supplying moisture from the moisture supply system 14 into the furnace and controlling the amount of moisture (HO) in the atmosphere inside the furnace. Even with this configuration, the reverse reaction of the above reaction formula (4) can be suppressed. Therefore, the atmosphere furnace (second embodiment) of the present invention removes oxygen (O2) from the atmosphere by supplying hydrogen (H2) gas, preventing oxidation reactions, and then controls the dew point by adjusting the amount of moisture supplied by the moisture supply system 14. In the atmosphere furnace (second embodiment) of the present invention, the moisture supply system 14 can be connected to any location in the furnace body 11, as described above. This is because there is no need to generate moisture using a high-temperature environment, as is the case with hydrogen gas and oxygen.

[0072] (4-2) Dew point control The controller 18 stores a set value for the dew point temperature in advance and also has a program related to dew point control stored therein, and can perform dew point control based on the measured dew point value obtained from the dew point meter 17 so that the measured value falls within the set value range. FIG. 4 is a flowchart showing a specific example of dew point control. In the dew point control, first, the dew point temperature is measured in the atmosphere furnace, and the measured value is acquired (step S21). Next, it is determined whether the measured dew point temperature is within a set range (step S22). If the dew point temperature is within the set range (Step S22; Yes), the current amount of water supply is maintained, and the operation is terminated.

[0073] If the dew-point temperature is outside the set range (step S22; No), it is determined whether the dew-point temperature falls below the set range (whether the dew-point temperature falls below the lower limit of the set value) (step S23). If the dew-point temperature is less than the lower limit of the set value and does not fall within the set range (step S23; Yes), the control valve 15 is operated to open, the amount of water supplied from the water supply system 14 is increased (step S24), and the dew-point temperature rises (step S25).

[0074] On the other hand, if the dew-point temperature is not within the set range (step S22; No) and the dew-point temperature is not below the set range (step S23; No), it is determined that the dew-point temperature exceeds the set range (the dew-point temperature exceeds the upper limit of the set value) (step S26). If the dew-point temperature exceeds the upper limit of the set value and exceeds the set range (step S26), the flow control valve 132 is operated to close, the amount of water supplied from the water supply system 14 is reduced (step S27), and the dew-point temperature drops (step S28).

[0075] After the dew-point temperature is increased or decreased (S25, S28), the dew-point temperature is measured again (step S21), and it is determined whether the dew-point temperature is within the set range (step S22). If the reacquired dew-point temperature is within the set range (step S22; Yes), the operation is terminated. If the reacquired dew-point temperature is not within the set range (step S22; No), the dew-point temperature is repeatedly increased or decreased (S25, S28) by adjusting the amount of moisture supplied from the moisture supply system 14 (S24, S27) until the dew-point temperature is within the set range.

[0076] (5) Gas exhaust system The atmosphere furnace 10 may further include a gas exhaust system. This gas exhaust system is the same as the (5) gas exhaust system of the above-mentioned [1] atmospheric furnace (first embodiment), and therefore a description thereof will be omitted.

[0077] [3] How to use the atmosphere furnace (1) The present invention is a method for using the atmospheric furnace 10 of the first embodiment to perform a brazing treatment on a brazing material and a base material as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is set to 3 vol% or more and 20 vol% or less, The controller regulates the purity of the nitrogen gas produced by the PSA nitrogen gas production equipment to between 97% and 99.5%, thereby controlling the dew point temperature inside the furnace to between 5°C and 40°C.

[0078] That is, the method (1) of using an atmospheric furnace is a brazing process using an atmospheric furnace 10 (see FIG. 1). In this brazing process, the surface of the base material needs to be wettable in order to bond the brazing filler metal to the base material, and the dew point temperature in the furnace is controlled to impart wettability to the surface of the base material. Regarding the workpiece, the brazing material and base material are not particularly limited and any material that is used in a normal brazing process can be used. Examples of the brazing material include copper-brass brazing, phosphorus copper brazing, silver brazing, aluminum brazing, nickel brazing, gold brazing, and palladium brazing. The base material may be one having a higher melting point than the brazing material, such as metals such as iron, copper, aluminum, titanium, silver, and tungsten, alloys of these metals, or ceramics.

[0079] In the brazing process, the hydrogen gas concentration in the atmosphere in the furnace is set to 3 vol% or more and 30 vol% or less, preferably 5 vol% or more and 25 vol% or less, and more preferably 7 vol% or more and 20 vol% or less. The concentration of hydrogen gas can be adjusted by operating the first adjustment valve 122 of the hydrogen gas supply system 12. The operation of this first adjustment valve 122 can also be performed by the controller 18.

[0080] In the brazing process, the dew point temperature inside the furnace is controlled by appropriately adjusting the purity of the nitrogen gas produced by the PSA device 16, increasing or decreasing the amount of oxygen mixed with the nitrogen gas and sent into the furnace, and controlling the amount of water produced by the reaction between oxygen and hydrogen gas. The purity of the nitrogen gas produced by the PSA device 16 is adjusted to 97% or more and 99.5% or less, thereby making it possible to control the dew point temperature inside the furnace to 5°C or more and 40°C or less. The purity of the nitrogen gas produced by the PSA device 16 can be controlled by operating the flow control valve 132 to adjust the flow rate of the nitrogen gas supplied from the PSA device 16 to the nitrogen gas supply system 13 . The purity of the nitrogen gas can be preferably 98% or more and 99% or less, and more preferably 98.5% or more and 99% or less.

[0081] [4] How to use the atmosphere furnace (2) The present invention is a method for using the atmospheric furnace 10 of the second embodiment to perform a brazing treatment on a brazing material and a base material as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is set to 3 vol% or more and 30 vol% or less, The controller adjusts the amount of moisture supplied from the moisture supply system so that the moisture concentration in the atmosphere inside the furnace is between 0.8 vol% and 6.5 vol%, thereby controlling the dew point temperature inside the furnace to between 5°C and 40°C.

[0082] That is, the method (2) of using an atmospheric furnace is a brazing process using an atmospheric furnace 10 (see FIG. 2). The brazing process, brazing material, and base material are as described above.

[0083] In the brazing process, the hydrogen gas concentration in the atmosphere in the furnace is set to 3 vol% or more and 30 vol% or less, preferably 5 vol% or more and 25 vol% or less, and more preferably 7 vol% or more and 20 vol% or less. In this brazing process, hydrogen gas is mainly used to remove oxygen remaining in the atmosphere inside the furnace, etc. Furthermore, the moisture generated by the reaction between hydrogen gas and oxygen can be used to adjust the dew point during the brazing process, thereby reducing the amount of moisture supplied by the moisture supply system 14.

[0084] During the brazing process, the controller 18 adjusts the amount of moisture supplied from the moisture supply system 14 so that the moisture concentration in the atmosphere inside the furnace is 0.8 vol% or more and 6.5 vol% or less, thereby controlling the dew point temperature inside the furnace to 5°C or more and 40°C or less. The amount of water supplied can be adjusted by operating the control valve 15. By adjusting the amount of water supplied, the concentration of water in the atmosphere inside the furnace can be set to preferably 1.0 vol% or more and 6.3 vol% or less, and more preferably 1.2 vol% or more and 6.1 vol% or less.

[0085] [5] How to use the atmosphere furnace (3) The present invention is a method for using the atmospheric furnace 10 of the second embodiment to perform bright annealing treatment on a stainless steel workpiece as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is 75 vol% or more, The controller adjusts the amount of moisture supplied from the moisture supply system so that the moisture concentration in the atmosphere inside the furnace is between 0.013 vol% and 0.08 vol%, thereby controlling the dew point temperature inside the furnace to between -50°C and -45°C.

[0086] That is, the method (3) of using an atmospheric furnace is a bright annealing treatment using an atmospheric furnace 10 (see FIG. 2). In this bright annealing process, stainless steel is used as the workpiece, and bright annealing is required to maintain the same luster on the surface of the workpiece as before annealing. To prevent the formation of oxide scale on the surface, annealing in a non-oxidizing atmosphere (non-oxidizing annealing) is required.

[0087] Bright annealing does not require any change in the purity of the nitrogen gas during the treatment, and therefore, the atmospheric furnace 10 (see FIG. 2) used for bright annealing is not particularly limited as to whether or not it is connected to the nitrogen gas supply system 13 and the PSA device 16. That is, in the atmosphere furnace 10 for bright annealing treatment, the nitrogen gas supply system 13 can be configured so as not to be connected to the PSA device 16. In the case where the PSA device 16 is not connected, the nitrogen tank 131 of the nitrogen gas supply system 13 can store nitrogen (N2) gas that has been produced elsewhere in advance. Alternatively, the nitrogen gas supply system 13 may be configured to be connected to a PSA unit 16. In the case of a configuration in which the PSA unit 16 is connected, the PSA unit 16 can maintain, for example, the produced nitrogen (N2) gas at a high purity without changing the flow rate.

[0088] In bright annealing, the lower limit of the hydrogen gas concentration in the atmosphere inside the furnace is 50 vol% or more. The lower limit of the hydrogen gas concentration can be preferably 75 vol% or more. The upper limit of the hydrogen gas concentration is not particularly limited, and for example, in order to suppress nitriding of stainless steel, the hydrogen gas concentration can be 100 vol% or less, that is, the furnace can be an atmosphere of only hydrogen gas. In this bright annealing process, hydrogen gas is used to remove oxygen from the atmosphere in the furnace to create an oxygen-free atmosphere. In addition, the moisture generated by the reaction between hydrogen gas and oxygen can be used to adjust the dew point, thereby reducing the amount of moisture supplied by the moisture supply system 14.

[0089] During the bright annealing treatment, the amount of moisture supplied from the moisture supply system 14 is adjusted by the controller 18 so that the moisture concentration in the atmosphere inside the furnace is 0.008 vol% or more and 0.02 vol% or less. At this time, the dew point temperature inside the furnace can be controlled to -50°C or more and -45°C or less. The amount of water supplied can be adjusted by operating the control valve 15. The moisture concentration in the atmosphere inside the furnace can be preferably set to 0.009 vol % or more and 0.015 vol % or less by adjusting the amount of moisture supplied. [Industrial Applicability]

[0090] The present invention can be used in a wide range of products and is particularly useful from the perspective of carbon neutrality. [Explanation of symbols]

[0091] 10; atmosphere furnace, 11; furnace body, 111; conveying device, 112; inlet, 113; outlet, 114; opening, 115; heating chamber, 116; cooling chamber, 117; front chamber, 118; rear chamber, 119; heating device, 12; hydrogen gas supply system, 121; hydrogen tank, 122; first adjusting valve, 13; nitrogen gas supply system, 131; nitrogen tank, 132; flow control valve, 133; pressure reducing valve, 132A; supply valve, 133A; second adjustment valve, 14;Moisture supply system, 141;Humidifier, 15;Control valve, 16;PSA nitrogen gas production device, 161;air supply device, 162;adsorption tank, 163;switching valve, 17; dew point meter, 18;Controller, 21; first gas exhaust system, 22; first exhaust valve, 23; second gas exhaust system, 24; second exhaust valve.

Claims

1. An atmospheric furnace in which a workpiece is heat-treated in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body that accommodates the workpiece; a hydrogen gas supply system connected to the furnace body; a nitrogen gas supply system connected to the furnace body; a PSA nitrogen gas production device connected to the nitrogen gas supply system and producing nitrogen gas by removing oxygen from air; a dew point meter attached to the furnace body to measure a dew point temperature inside the furnace; a controller that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter; The controller adjusts the purity of the nitrogen gas produced by the PSA nitrogen gas production device, increases or decreases the amount of oxygen mixed with the nitrogen gas and sent into the furnace of the furnace body, and increases or decreases the amount of moisture generated in the atmosphere inside the furnace by the reaction between the oxygen and the hydrogen gas supplied into the furnace, thereby controlling the dew point temperature.

2. The furnace body includes a heating chamber for heating the workpiece and a cooling chamber for cooling the workpiece, the hydrogen gas supply system and the nitrogen gas supply system are connected to the heating chamber; 2. The atmospheric furnace according to claim 1, wherein the cooling chamber and the heating chamber are internally connected to each other, and atmospheric gas is diverted from the heating chamber.

3. In the furnace body, an end portion on the side where the workpiece is inserted into the furnace is defined as an inlet end portion, and an end portion on the side where the workpiece is removed from the furnace is defined as an outlet end portion, a first gas exhaust system connected to an inlet end of the furnace body to exhaust gas from within the furnace, and a first exhaust valve connected to the first gas exhaust system to adjust the amount of exhaust; a second gas exhaust system connected to the outlet end of the furnace body to exhaust gas from the furnace, and a second exhaust valve connected to the second gas exhaust system to adjust the amount of exhaust; 3. The atmospheric furnace according to claim 2, wherein the controller adjusts the exhaust volume by operating the exhaust valves of the first gas exhaust system and / or the second gas exhaust system, and controls the amount of atmospheric gas diverted from the heating chamber to the inlet end or the outlet end of the furnace body.

4. A method of using the atmosphere furnace according to claim 1 to perform a brazing treatment on a brazing material and a base material as a heat treatment, the method comprising: The concentration of hydrogen gas in the atmosphere in the furnace is set to 3 vol% or more and 30 vol% or less, A method for using an atmospheric furnace, characterized in that the purity of nitrogen gas produced by a PSA nitrogen gas production device is adjusted by a controller to 97% or more and 99.5% or less, thereby controlling the dew point temperature inside the furnace to 5°C or more and 40°C or less.

5. An atmospheric furnace for heat-treating a workpiece in an atmosphere filled with hydrogen gas and nitrogen gas as atmospheric gases, a furnace body that accommodates the workpiece; a hydrogen gas supply system connected to the furnace body; a nitrogen gas supply system connected to the furnace body; a moisture supply system connected to the furnace body to supply moisture into the furnace, and a control valve connected to the moisture supply system; a dew point meter attached to the furnace body to measure a dew point temperature inside the furnace; a controller that controls the dew-point temperature in accordance with the dew-point temperature acquired from the dew-point meter; the controller controls the dew-point temperature by operating the control valve and adjusting the amount of moisture supplied from the moisture supply system in accordance with the dew-point temperature acquired from the dew-point meter; The furnace body includes a heating chamber for heating the workpiece and a cooling chamber for cooling the workpiece, the hydrogen gas supply system and the nitrogen gas supply system are connected to the heating chamber; The cooling chamber and the heating chamber are in communication with each other, and atmospheric gas is diverted from the heating chamber, In the furnace body, an end portion on the side where the workpiece is inserted into the furnace is defined as an inlet end portion, and an end portion on the side where the workpiece is removed from the furnace is defined as an outlet end portion, a first gas exhaust system connected to an inlet end of the furnace body to exhaust gas from within the furnace, and a first exhaust valve connected to the first gas exhaust system to adjust the amount of exhaust; a second gas exhaust system connected to the outlet end of the furnace body to exhaust gas from the furnace, and a second exhaust valve connected to the second gas exhaust system to adjust the amount of exhaust; The controller adjusts the exhaust volume by operating the exhaust valves of at least one of the first gas exhaust system and the second gas exhaust system, thereby controlling the amount of atmospheric gas diverted from the heating chamber to the inlet end or outlet end of the furnace body.

6. A method of using the atmosphere furnace according to claim 5 to perform a brazing treatment on a brazing material and a base material as a heat treatment, comprising: The concentration of hydrogen gas in the atmosphere in the furnace is set to 3 vol% or more and 30 vol% or less, A method for using an atmospheric furnace, characterized in that a controller adjusts the amount of moisture supplied from a moisture supply system so that the moisture concentration in the atmosphere inside the furnace is 0.8 vol% or more and 6.5 vol% or less, thereby controlling the dew point temperature inside the furnace to 5°C or more and 40°C or less.

7. A method for using the atmosphere furnace according to claim 5 to bright anneal a stainless steel workpiece as a heat treatment, comprising: The concentration of hydrogen gas in the atmosphere inside the furnace is set to 50 vol% or more, A method for using an atmospheric furnace, characterized in that a controller adjusts the amount of moisture supplied from a moisture supply system so that the moisture concentration in the atmosphere inside the furnace is 0.008 vol% or more and 0.02 vol% or less, thereby controlling the dew point temperature inside the furnace to -50°C or more and -45°C or less.

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