Heat treatment facility and carburizing and quenching method

Abstract

To provide a heat treatment facility capable of solving or reducing problems in the case of performing gas quenching or press quenching to a group of workpieces subjected to carburizing treatment at a time in a multi-stage stacked state.SOLUTION: A heat treatment facility 1 includes a vacuum chamber 2, a plurality of carburizing chambers 5 arranged side by side inside the vacuum chamber 2, a pre-quenching holding chamber 7 that houses a workpiece W and holds the workpiece W at a predetermined temperature, a transfer chamber 8 adjacent to the pre-quenching holding chamber 7, and a gas quenching chamber 9 adjacent to the transfer chamber 8. A first workpiece transfer mechanism 64 provided inside the vacuum chamber 2 transfers the workpiece W stacked in a plurality of stages via trays 61 to the carburizing chambers 5 and the pre-quenching holding chamber 7. A second workpiece transfer mechanism 74 provided inside the transfer chamber 8 separates the workpieces W stacked in a plurality of stages in the pre-quenching holding chamber 7 for each tray and transfers them to the gas quenching chamber 9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat treatment facility for heat treating a metal workpiece and a carburizing and quenching method using the heat treatment facility. [Background technology]

[0002] In recent years, gas quenching using an inert gas has been adopted with the aim of reducing distortion and cutting costs by eliminating post-cleaning processes. For example, Patent Document 1 below discloses a vacuum quenching treatment facility that performs a series of treatments from carburizing to gas quenching on workpieces (steel part materials, etc.) placed on a tray. Gas quenching has inferior hardenability compared to conventional oil quenching, so there is a problem that the workpieces to which gas quenching can be applied are limited. Therefore, Patent Document 1 below is configured with both a gas cooling chamber and a liquid cooling chamber, so that either gas quenching or oil quenching can be selected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-209554 Summary of the Invention [Problem to be solved by the invention]

[0004] In carburizing, an upstream process of quenching, it is effective to process many workpieces in a multi-tiered state at once to improve manufacturing efficiency. However, if gas quenching is performed in a multi-tiered state like in carburizing, a sufficient cooling rate cannot be obtained, resulting in a decrease in hardenability. In some cases, press quenching is performed as a quenching process following carburizing. However, press quenching requires that the workpieces be quenched one by one. If many workpieces are carburized at once, the workpieces W are exposed to the outside air for a long time while waiting to be transported to the press quenching device, which can cause problems such as decarburization and uneven temperature distribution in the workpieces before press quenching.

[0005] The present invention has been made in light of the above circumstances and has as its object to provide heat treatment equipment that can eliminate or mitigate the problems that arise when a group of workpieces that have been carburized at one time in a multi-tiered state are gas quenched or press quenched. [Means for solving the problem]

[0006] The heat treatment equipment according to the first aspect of the present invention is defined as follows: A heat treatment facility for performing heat treatment on a metal workpiece, a vacuum chamber; a plurality of carburizing chambers arranged side by side inside the vacuum chamber; a pre-quenching holding chamber that accommodates the workpiece and holds it at a predetermined temperature; a transfer chamber adjacent to the pre-quenching holding chamber; a gas quenching chamber or a pressure recovery chamber adjacent to the transfer chamber; a first workpiece transport mechanism provided inside the vacuum chamber for transferring the workpiece between the carburizing chamber and the pre-quenching holding chamber; a second workpiece transport mechanism provided inside the transport chamber for transferring the workpiece between the pre-quenching holding chamber and the gas quenching chamber or the pressure recovery chamber; Equipped with the first workpiece transport mechanism has a first control unit that controls the operation of transporting the workpieces stacked in multiple stages via trays to the carburizing chamber and the pre-quenching holding chamber; The second workpiece transport mechanism has a second control unit that controls the operation to separate the workpieces stacked in multiple layers in the pre-quenching holding chamber into trays and transport them to the gas quenching chamber or the pressure recovery chamber.

[0007] In the heat treatment equipment of the first aspect defined as above, a group of workpieces that have been carburized at one time in a multi-tiered state can be separated into trays using the second workpiece transport mechanism, and small amounts of workpieces on one tray can be sequentially supplied to the downstream gas quenching chamber or pressure recovery chamber, thereby eliminating or alleviating the problems that arise when a group of workpieces that have been carburized at one time in a multi-tiered state are gas quenched or pressurized.

[0008] Here, a second heating chamber having a heating means and a cooling means for performing heat treatment on the workpiece treated in the carburizing chamber (first heating chamber) can be further provided inside the vacuum chamber (second aspect). In this way, intermediate cooling and reheating of the carburized workpiece can be carried out successively.

[0009] A carburizing and quenching method according to a third aspect of the present invention is defined as follows: A method for performing carburizing and quenching using the heat treatment equipment according to the first aspect, a step of loading the workpieces stacked in multiple stages via trays into the carburizing chamber and subjecting them to vacuum carburizing; and a step of separating the workpieces stacked in a plurality of stages into trays after the vacuum carburizing treatment and transporting them sequentially to the gas quenching chamber or the pressure recovery chamber. The carburizing and quenching method of the third aspect thus defined provides the same effects as those of the first aspect. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic overall configuration of a heat treatment facility according to an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view of the heat treatment equipment shown in FIG. 1 taken along line II-II. [Figure 3] (A) is an enlarged view of the carburizing chamber in Figure 1. (B) is an enlarged view of the carburizing chamber in Figure 2. [Figure 4] 2(A) is an enlarged view of the second heating chamber in FIG. 1. FIG. 2(B) is an enlarged view of the second heating chamber in FIG. [Figure 5] 1 is a diagram showing a stack of trays holding a plurality of workpieces W. FIG. [Figure 6] FIG. 4 is an explanatory diagram of a first workpiece transport mechanism. [Figure 7] FIG. 10 is an explanatory diagram of a second workpiece transport mechanism. [Figure 8] FIG. 2 is a diagram showing an example of a heat pattern for carburizing and quenching. [Figure 9] FIG. 10 is an explanatory diagram of a modified example in which a pressure recovery chamber is provided instead of the gas quenching chamber. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 shows a schematic overall configuration of a heat treatment facility according to one embodiment of the present invention. In the figure, reference numeral 1 denotes a heat treatment facility that performs a series of heat treatments, from carburizing to gas quenching, on a workpiece W such as a steel part material. The facility is provided with an inlet-side purge chamber 4, carburizing chambers 5A, 5B, and 5C, second heating chambers 6A, 6B, and 6C, a pre-quenching holding chamber 7, a transfer chamber 8, and a gas quenching chamber 9, in the order in which the workpiece W is transported.

[0012] This heat treatment equipment 1 is equipped with a box-shaped steel vacuum chamber 2. Vacuum chamber 2 is pressure-resistant and can be depressurized to a predetermined vacuum level. Inside vacuum chamber 2, carburizing chambers 5A, 5B, and 5C and second heating chambers 6A, 6B, and 6C are arranged vertically, and a first workpiece transfer mechanism 64 is also provided, which moves vertically to transfer workpieces W.

[0013] In addition, an inlet side purge chamber 4 and a pre-quenching holding chamber 7 are provided on the side wall of the vacuum chamber 2 opposite the carburizing chambers 5A, 5B, 5C and the second heating chambers 6A, 6B, 6C across the first workpiece transport mechanism 64. In the following description, the carburizing chambers 5A, 5B, and 5C may be collectively referred to as the "carburizing chamber 5." Furthermore, the second heating chambers 6A, 6B, and 6C may be collectively referred to as the "second heating chamber 6."

[0014] FIG. 3 is a diagram showing the schematic configuration of the carburizing chamber 5A. The carburizing chamber 5A is a compartment in which the workpiece W is heated to a predetermined temperature (e.g., 1050°C) in a vacuum atmosphere for carburizing. The carburizing chamber 5A has heat-resistant insulating material that forms a box-shaped insulating wall 11. The side wall 11a of the insulating wall 11 facing the first workpiece transfer mechanism 64 (see FIG. 3(A)) serves as an opening / closing door that opens and closes when the workpiece W is transferred, and is configured to be rotatable around the axis 14 of the opening / closing device 13. The processing chamber inside the insulating wall 11 is provided with a rack member 15 that holds the workpiece W, and a heater 17 as heating means.

[0015] One end of a vacuum exhaust pipe 19 extending from a vacuum pump 18 (see FIG. 1) is connected to the carburizing chamber 5A, making it possible to reduce the pressure inside the carburizing chamber 5A and further inside the vacuum chamber 2 to a predetermined vacuum level. The carburizing chamber 5A is also provided with a nozzle (not shown) for supplying carburizing gas such as acetylene gas to the processing chamber inside the insulating wall 11. The carburizing chamber 5A has been described above, but the other carburizing chambers 5B and 5C have the same configuration.

[0016] FIG. 4 is a diagram showing the schematic configuration of the second heating chamber 6A. The second heating chamber 6A is a compartment in which the workpiece W carburized in one of the carburizing chambers 5A, 5B, or 5C is cooled to a target intermediate cooling temperature (e.g., 600°C) in a vacuum atmosphere and then reheated to a target secondary heating temperature (e.g., 850°C) and maintained there. The second heating chamber 6A, like the carburizing chambers 5A, 5B, and 5C, has heat-resistant insulating material, which forms a box-shaped insulating wall 21. The side wall 21a of the insulating wall 21 facing the first workpiece transport mechanism 64 (see FIG. 4(A)) serves as an opening / closing door that opens and closes when transferring the workpiece W, and is configured to be rotatable around an axis 24 of an opening / closing device 23. The processing chamber inside the insulating wall 21 is provided with a rack member 25 for holding the workpiece W and a heater 27 as heating means.

[0017] In addition, one end of a vacuum exhaust pipe 19 extending from a vacuum pump 18 (see Figure 1) is connected to the second heating chamber 6A, making it possible to reduce the pressure inside the second heating chamber 6A and further inside the vacuum chamber 2 to a predetermined vacuum level.

[0018] The second heating chamber 6A is provided with a water-cooled panel 30 as cooling means for cooling the workpiece W in a vacuum atmosphere. Openings 31 and 32 are provided at the top and bottom of the insulating wall 21 of the second heating chamber 6A, respectively, and the water-cooled panels 30 are disposed above the opening 31 and below the opening 32 so as to face the top and bottom surfaces of the workpiece W via these openings 31 and 32. The water-cooled panel 30 has a cooling water flow path formed therein for circulating cooling water, and by circulating the cooling water inside the water-cooled panel 30, heat generated from the high-temperature workpiece W is recovered.

[0019] As shown in Figure 4(B), a shutter mechanism 40 is provided between the heater 27 and the water-cooled panel 30. The shutter mechanism 40 includes a heat shield plate 41 made of a heat insulating material that opens and closes the opening 31 or 32, and a cylinder device 43 that opens and closes the heat shield plate 41. The heat shield plate 41 is made up of halves 41a and 41b, which move in opposite directions from near the center of the opening 31 or 32 to open the opening 31 or 32.

[0020] A pair of shutter mechanisms 40, 40 provided above and below open the openings 31, 32 when cooling the workpiece W, allowing the water-cooled panel 30 to radiately cool the workpiece W. On the other hand, when heating the workpiece W with the heater 27, the openings 31, 32 are closed by a heat shield 41 to prevent the water-cooled panel 30 from being damaged by the heat from the heater 27.

[0021] This second heating chamber 6A is provided with a radiation thermometer (not shown) for measuring the temperature of the workpiece W contained therein, and the opening and closing operations of the shutter mechanism 40 are controlled based on the temperature of the workpiece W measured by the radiation thermometer. The configuration of the second heating chamber 6A has been described above, but the other second heating chambers 6B and 6C have the same configuration.

[0022] Next, the inlet side purge chamber 4 and the pre-quenching holding chamber 7 will be described. The entrance purge chamber 4 is a compartment that first receives the workpieces W sent from the upstream process. The entrance purge chamber 4 has a pressure-resistant housing 45 attached to the opening 2a in the side wall of the vacuum chamber 2. The housing 45 is formed with an outer opening 46 for loading the workpieces W sent from the upstream process, and an inner opening 47 that communicates with the vacuum chamber 2. These openings 46, 47 are provided with openable and closable doors 48, 49, respectively. The door 48 is capable of airtightly closing the outer opening 46, and the door 49 is capable of airtightly closing the inner opening 47. A rack member 50 for holding the loaded workpieces W is provided inside the entrance purge chamber 4.

[0023] The inlet-side purge chamber 4, the pre-quenching holding chamber 7, the transfer chamber 8, and the gas quenching chamber 9, which will be described later, are all connected to a vacuum exhaust pipe extending from a vacuum pump (not shown) and a pipe for supplying N2 gas to introduce atmospheric gas used for restoring pressure, etc. In the inlet side purge chamber 4, the workpiece W is loaded through the outer opening 46, and when the door 48 is closed, the air inside the inlet side purge chamber 4 is exhausted to the outside of the chamber via the vacuum pump.

[0024] The pre-quenching holding chamber 7 is a compartment for holding the workpiece W processed in the second heating chamber 6. The pre-quenching holding chamber 7 has a pressure-resistant housing 52 attached to the opening 2b in the side wall of the vacuum chamber 2. The housing 52 has an entrance opening 53 communicating with the vacuum chamber 2 and an exit opening 54 communicating with the transfer chamber 8. These openings 53, 54 are provided with openable and closable doors 55, 56, respectively. The door 55 is capable of airtightly closing the entrance opening 53, and the door 56 is capable of airtightly closing the exit opening 54. The pre-quenching holding chamber 7 also has a heat-resistant insulating material that forms a box-shaped insulating wall 57. Inside the insulating wall 57, a rack member 58 for holding the loaded workpiece W and a heater 59 as heating means are provided.

[0025] In this embodiment, the workpieces W are transported while being placed on a tray. Fig. 5 is a diagram showing a tray stack 60 that holds a plurality of workpieces W stacked vertically. The tray stack 60 shown in the figure includes a plurality of lattice-shaped trays 61 (here, three trays 61A, 61B, and 61C), and a plurality of workpieces W are placed on each tray 61. Short column-shaped spacers 62 are erected at the four corners of the trays 61B and 61C except for the top tray 61A, and the trays 61 are stacked vertically via the spacers 62. As shown in Fig. 5(A), a gap δ is secured between the trays 61A and 61B and the workpiece W positioned directly below them, allowing a transport arm 75, which will be described later, to be inserted.

[0026] 5(A), the workpieces W are loaded from the upstream process into the inlet-side purge chamber 4 in the form of a tray stack 60. Thereafter, the workpieces W are transported in the form of a tray stack 60 by a first workpiece transport mechanism 64 to the carburizing chamber 5, the second heating chamber 6, and the pre-quenching holding chamber 7.

[0027] Furthermore, as shown in Figure 5(B), the tray stack 60 can be separated into individual trays, and the workpieces W transported to the pre-quenching holding chamber 7 in the form of the tray stack 60 are separated into individual trays by the second workpiece transport mechanism 74 and transported to the gas quenching chamber 9 on a tray-by-tray basis.

[0028] Next, we will explain the first workpiece transfer mechanism 64. As shown in Fig. 1, the first workpiece transfer mechanism 64 is provided between the group of carburizing chambers 5 and second heating chambers 6 arranged in a row on the left side of the figure, and the inlet-side purge chamber 4 and pre-quenching holding chamber 7 arranged on the right side of the figure. The first workpiece transport mechanism 64 is composed of a platform 65 supported by guide rails (not shown) so that it can move up and down, chains 66, 67 that move the platform 65 up and down, and a telescopic arm 68 that is arranged on the platform 65 and can extend and retract horizontally.

[0029] 6, the telescopic arm 68 includes a base arm 69, an intermediate arm 70 supported so as to be movable in the longitudinal direction relative to the base arm 69, and an upper arm 71 supported so as to be movable in the longitudinal direction relative to the intermediate arm 70. The telescopic arm 68 is extendable into the carburizing chamber 5 and the second heating chamber 6, and is also extendable into the inlet purge chamber 4 and the pre-quenching holding chamber 7 located on the opposite side of the carburizing chamber 5 and the second heating chamber 6.

[0030] 6, the first workpiece transfer mechanism 64 transfers workpieces W stacked in multiple layers as a tray stack 60 to the carburizing chamber 5, the second heating chamber 6, and the pre-quenching holding chamber 7. For example, the operation of the first workpiece transfer mechanism 64 when transferring the tray stack 60 loaded in the entrance purge chamber 4 to the carburizing chamber 5B is as follows. The first workpiece transfer mechanism 64 extends the telescopic arm 68 into the entrance purge chamber 4 at a position opposite the entrance purge chamber 4, inserts its upper arm 71 into the space below the tray stack 60, and then raises the telescopic arm 68 a small distance to place the tray stack 60 on the telescopic arm 68 and remove the tray stack 60 from the entrance purge chamber 4. Then, with the tray stack 60 still loaded, the telescopic arm 68 is pulled back onto the platform 65, and the platform 65 is raised to a position opposite the carburizing chamber 5B, which is the other end of the transfer. Next, the telescopic arm 68 is extended into the carburizing chamber 5B, and the tray stack 60 is transferred onto the rack member 15 inside the carburizing chamber 5B. This series of operations in the first workpiece transfer mechanism 64 is controlled by a first control unit (not shown), which constitutes a part of the first workpiece transfer mechanism 64.

[0031] Next, the transfer chamber 8 and the second workpiece transfer mechanism 74 provided within that chamber will be described. The transfer chamber 8 is located adjacent to the pre-quenching holding chamber 7, downstream in the transfer direction from the pre-quenching holding chamber 7. One of the open ends of the housing 73 of the transfer chamber 8 is connected to the outlet opening 54 of the pre-quenching holding chamber 7, and the other is connected to the inlet opening 88 of the gas quenching chamber 9. The transfer chamber 8 is provided with the second workpiece transfer mechanism 74 that transfers the workpiece W from the pre-quenching holding chamber 7 to the gas quenching chamber 9.

[0032] The second workpiece transport mechanism 74 includes a telescopic arm 75 that is extendable and retractable in the horizontal direction, and a lifting unit 80 that raises and lowers the telescopic arm 75. As shown in Fig. 7, the telescopic arm 75 includes a base arm 76, an intermediate arm 77 that is supported so as to be movable in the longitudinal direction relative to the base arm 76, and an upper arm 78 that is supported so as to be movable in the longitudinal direction relative to the intermediate arm 77. The telescopic arm 75 is extended from the contracted state shown in FIG. 1 to the upstream side in the conveying direction (to the left in the figure) or the downstream side in the conveying direction (to the right in the figure) as shown in FIG. 7, with the intermediate arm 77 and the upper arm 78 working in conjunction with each other, and is also driven to be pulled back from the extended state to the contracted state shown in FIG. 1.

[0033] The lifting unit 80 that enables the telescopic arm 75 to move up and down includes a base 81, a lifting platform 82, a pair of arms 83A, 83B, and a lifting drive unit 84 that generates a driving force during lifting. The output shaft of the lifting drive unit 84 is connected to the lifting platform 82, and the telescopic arm 75 is raised and lowered together with the lifting platform 82. The pair of arms 83A, 83B are used to raise and lower the lifting platform 82 while maintaining it horizontal, and are configured by two arms rotatably connected at the center. One end of the arm 83A is rotatably connected to the lifting platform 82, and the other end is slidably and rotatably connected to the base 81, while one end of the other arm 83B is rotatably connected to the base 81, and the other end is slidably and rotatably connected to the lifting platform 82.

[0034] The second workpiece transport mechanism 74 separates the tray stack 60 into individual trays, and transports the small number of workpieces W placed on each tray to the gas quenching chamber 9 in sequence. For example, when transporting a workpiece W placed on the top tray 61A of the tray stack 60 loaded in the pre-quenching holding chamber 7 to the gas quenching chamber 9, the operation of the second workpiece transport mechanism 74 is as follows. The second workpiece transport mechanism 74 raises the lifting platform 82 and telescopic arm 75 to a predetermined height to separate the tray 61A from the tray stack 60, and then extends the telescopic arm 75 into the pre-quenching holding chamber 7. Then, the upper arm 78 is inserted into the gap δ (see FIG. 5A) formed directly below the tray 61A in the tray stack 60, and the telescopic arm 75 is then raised a small distance to transfer the tray 61A onto the telescopic arm 75, and the tray 61A and the workpiece W on the tray 61A are removed from the pre-quenching holding chamber 7. Then, with the tray 61A loaded, the telescopic arm 75 is extended into the gas quenching chamber 9, which is the other side of the transfer, and the telescopic arm 75 is lowered a small distance, whereby the tray 61A and the workpiece W are placed on the rack member 92 inside the gas quenching chamber 9 (see FIG. 1). The subsequent operations of transporting the workpiece W on tray 61B and the operation of transporting the workpiece W on tray 61C are basically the same as those for tray 61A. This series of operations in second workpiece transport mechanism 74 is controlled by a second control unit (not shown) that constitutes part of second workpiece transport mechanism 74.

[0035] Next, the gas quenching chamber 9 adjacent to the transfer chamber 8 will be described. The gas quenching chamber 9 has a pressure-resistant housing 87, which is formed with an entrance opening 88 for loading the workpiece W from the transfer chamber 8 side, and an exit opening 89 formed in a position opposite the entrance opening 88. These openings 88, 89 are provided with openable and closable doors 90, 91, respectively. The door 90 is capable of airtightly closing the entrance opening 88, and the door 91 is capable of airtightly closing the exit opening 89. A rack member 92 for holding the loaded workpiece W is provided inside the gas quenching chamber 9.

[0036] A gas cooling section 96 equipped with a gas cooler 94 and a fan 95 for circulating cooling gas is provided above the gas quenching chamber 9. An opening (mesh-shaped opening) (not shown) is provided in the housing 87 of the gas quenching chamber 9, which is in contact with the gas cooling section 96, and the gas cooling section 96 and the gas quenching chamber 9 are configured to communicate with each other via this opening. By circulating cooling gas (N2 gas) between the gas cooling section 96 and the gas quenching chamber 9, gas quenching of the workpiece W accommodated inside the gas quenching chamber 9 is possible. In gas quenching, the hardenability can be improved by increasing the pressure of the cooling gas, so the gas quenching chamber 9 is designed to have sufficient strength as a pressure vessel to accommodate the gas pressure used.

[0037] Next, a series of processing operations in the heat treatment equipment 1 will be described using an example in which carburizing and quenching is performed using the heat pattern shown in FIG. First, the workpieces W sent from the upstream process are loaded into the entrance purge chamber 4 as a tray stack 60 through the opening 46. The door 48 of the entrance purge chamber 4 is closed, and a vacuum pump is used to reduce the pressure inside the chamber, releasing the atmosphere inside the chamber. Once the pressure inside the entrance purge chamber 4 has been reduced to the same level as the pressure inside the vacuum chamber 2 and the door 49 is opened, the first workpiece transport mechanism 64 receives the tray stack 60 from the entrance purge chamber 4 and transports it to one of the carburizing chambers 5 (here, carburizing chamber 5B). The tray stack 60 is then loaded into carburizing chamber 5B and set on the rack member 15. Once the tray stack 60 is loaded into carburizing chamber 5B, the workpieces W are heated to the target temperature (here, 1050°C) by radiant heating from the heater 17 in a vacuum atmosphere, and carburizing gas is supplied into the chamber to perform the carburizing process.

[0038] After the carburizing process in carburizing chamber 5B is completed, first workpiece transport mechanism 64 receives workpieces W in the form of tray stack 60 from carburizing chamber 5B and transports tray stack 60 to a position in second heating chamber 6 (second heating chamber 6A in this case). Then, tray stack 60 is loaded into second heating chamber 6A and set on rack member 25.

[0039] After the workpiece W is placed in the second heating chamber 6A, the workpiece W is cooled to the desired intermediate cooling temperature (here, 600°C) by the water-cooled panel 30 in the second heating chamber 6A, and then the workpiece W is reheated to the target secondary heating temperature (850°C) by the heater 27 and maintained at that temperature.

[0040] After the heat treatment in the second heating chamber 6A is completed, the first workpiece transport mechanism 64 receives the workpieces W in the second heating chamber 6A in the form of a tray stack 60, transports the tray stack 60 to the position of the pre-quenching holding chamber 7, and sets it on the rack member 58 in the pre-quenching holding chamber 7. In the pre-quenching holding chamber 7, the workpieces W are maintained at the target secondary heating temperature (850°C) by a heater 59 in a vacuum atmosphere.

[0041] Then, with the door 56 of the pre-quenching holding chamber 7 open, the telescopic arm 75 of the second workpiece transport mechanism 74 provided in the transport chamber 8 is extended into the pre-quenching holding chamber 7, and the uppermost tray 61A of the tray stack 60 is separated from the other trays and removed from the pre-quenching holding chamber 7. Then, with the door 90 of the gas quenching chamber 9 open, the telescopic arm 75 is extended into the gas quenching chamber 9, and the tray 61A separated from the tray stack 60 and the workpiece W on the tray 61A are set on the rack member 92 inside the gas quenching chamber 9.

[0042] Thereafter, with the door 90 closed, the gas quenching chamber 9 performs gas quenching by applying the cooling gas (N2 gas) introduced into the chamber 9 to the workpiece W. The quenched workpiece W is discharged together with the tray 61A from the outlet opening 89 to the outside of the facility. After the quenched workpieces W and trays 61A are discharged, the remaining trays 61B and 61C held in the pre-quenching holding chamber 7 are sequentially separated and removed by the second workpiece transport mechanism 74, and the removed trays and the workpieces W on them are transported to the gas quenching chamber 9 where gas quenching is performed.

[0043] As described above, in the heat treatment equipment 1 of this embodiment, the group of workpieces contained in the tray stack 60 that have been carburized at once in a multi-tiered state can be separated into individual trays 61 using the second workpiece transport mechanism 74, and small amounts of workpieces W placed on one tray 61 can be sequentially supplied to the downstream gas quenching chamber 9.This eliminates or reduces the problem of reduced hardenability that occurs when a group of workpieces that have been carburized at once in a multi-tiered state are gas quenched as is.

[0044] In the heat treatment equipment 1 of this embodiment, a second heating chamber 6 having a heater 27 and a water-cooled panel 30 is provided inside the vacuum chamber 2, and heat treatment is performed on the workpiece W carburized in the carburizing chamber 5. Therefore, intermediate cooling and reheating of the carburized workpiece W can be carried out continuously, and the coarsening of crystal grains that accompanies vacuum carburizing can be suppressed.

[0045] 9 is an explanatory diagram of a modified example in which a pressure recovery chamber 9B is provided instead of the gas quenching chamber 9. In the above embodiment, gas quenching is performed after carburizing treatment, but in the case of performing press quenching, in which quenching is performed while pressing after carburizing treatment, a pressure recovery chamber 9B can be provided instead of the gas quenching chamber 9, as shown in FIG. 9. In the example of FIG. 9, a transfer robot 99 and a press quenching device 100 are provided separately from the heat treatment equipment 1.

[0046] 9, the pressure recovery chamber 9B, located adjacent to the transfer chamber 8, is a compartment responsible for restoring pressure when the workpiece W, which has been carburized under vacuum, is removed to the outside. A vacuum exhaust pipe extending from a vacuum pump (not shown) and a N2 gas supply pipe for introducing the atmospheric gas used for restoring pressure are connected to the pressure recovery chamber 9B. A heater for maintaining the temperature may be installed in the pressure recovery chamber 9B. 9, in a vacuum atmosphere, a tray 61 separated from the tray stack 60 held in the pre-quenching holding chamber 7 and the workpiece W placed thereon are transferred to the pressure-recovery chamber 9B by the second workpiece transfer mechanism 74. Then, after the door 90 is closed in the pressure-recovery chamber 9B, atmospheric gas (N2 gas) is introduced into the chamber to restore pressure. After the pressure is restored, the workpiece W is removed from the pressure-recovery chamber 9B by the transfer robot 99 and transferred to the pressurization apparatus 100, where it is quenched.

[0047] 9 configured as described above, only a small number of workpieces W placed on one tray can be restored to pressure and removed as needed. Therefore, when the workpieces W are transported and quenched one by one to perform pressurization, the time that the workpieces W are exposed to air during the process of being restored to pressure and transported to the press quenching apparatus 100 can be kept short, and problems such as decarburization and deterioration of temperature distribution in the workpieces W before pressurization can be significantly reduced.

[0048] The above detailed description of the embodiments and their modifications of the present invention is merely illustrative. For example, the number of carburizing chambers and second heating chambers arranged side by side in the vacuum chamber and their arrangement direction are not limited to the above embodiments and can be modified as appropriate. Furthermore, if intermediate cooling following carburizing is not performed, a configuration that does not include a second heating chamber can be adopted. Furthermore, the configuration of the second workpiece transport mechanism that separates workpieces stacked in multiple layers into individual trays is not limited to the above embodiments and can be modified as appropriate as needed. The present invention can be configured in various modified forms without departing from its spirit. [Explanation of symbols]

[0049] 1. Heat treatment equipment 2. Vacuum chamber 5(5A,5B,5C) Carburizing chamber 6(6A,6B,6C) 2nd heating chamber 7 Pre-quenching holding chamber 8 Transport Room 9 Gas quenching chamber 9B Decompression chamber 60 tray stack 61(61A,61B,61C) Tray 64 First processed item transport mechanism 74 Second processed item transport mechanism W Processing object

Claims

1. A heat treatment facility for performing heat treatment on a metal workpiece, a vacuum chamber; a plurality of carburizing chambers arranged side by side inside the vacuum chamber; a pre-quenching holding chamber that accommodates the workpiece and holds it at a predetermined temperature; a transfer chamber adjacent to the pre-quenching holding chamber; a gas quenching chamber or a pressure recovery chamber adjacent to the transfer chamber; a first workpiece transfer mechanism provided inside the vacuum chamber for transferring the workpiece between the carburizing chamber and the pre-quenching holding chamber; a second workpiece transport mechanism provided inside the transport chamber for transferring the workpiece between the pre-quenching holding chamber and the gas quenching chamber or the pressure recovery chamber; Equipped with the first workpiece transport mechanism has a first control unit that controls the operation of transporting the workpieces stacked in multiple stages via trays to the carburizing chamber and the pre-quenching holding chamber; The second workpiece transport mechanism has a second control unit that controls the operation of separating the workpieces stacked in multiple layers in the pre-quenching holding chamber into trays and transporting them to the gas quenching chamber or the pressure recovery chamber.

2. 2. The heat treatment facility according to claim 1, further comprising a second heating chamber provided inside said vacuum chamber, said second heating chamber having a heating means and a cooling means for performing heat treatment on said workpiece treated in said carburizing chamber.

3. A method for performing carburizing and quenching using the heat treatment equipment according to claim 1, comprising: a step of loading the workpieces stacked in multiple stages via trays into the carburizing chamber and subjecting them to vacuum carburizing; and after the vacuum carburizing treatment, separating the workpieces stacked in multiple stages into trays and transporting them sequentially to the gas quenching chamber or the pressure recovery chamber.

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