Heat treatment equipment

Abstract

This invention provides a heat treatment system that can solve the problem of not being able to distribute the process gas supplied to the treatment chamber to the center of the chamber. [Solution] The heat treatment equipment 1 supplies process gas into a processing chamber 26 in which the workpiece W is housed, and performs heat treatment on the workpiece W. The heat treatment equipment 1 includes a first process gas supply means 175 that supplies process gas through a first nozzle 38 fixedly positioned around the processing chamber 26, and a second process gas supply means 176 that supplies process gas through a second nozzle 182 that is movable relative to the processing chamber 26.

Description

Technical Field

[0001] The present invention relates to a heat treatment facility that supplies a process gas into a treatment chamber in which a workpiece is accommodated and performs heat treatment on the workpiece.

Background Art

[0002] In workpieces made of metal materials such as steel, as surface treatments for improving characteristics such as surface hardening, carburizing treatment for introducing C atoms into the surface layer of the metal material, nitriding treatment for introducing N atoms into the surface layer, carbonitriding treatment for introducing both C atoms and N atoms into the surface layer, etc. are performed. For example, Patent Document 1 below discloses a heat treatment facility that performs nitriding following vacuum carburizing.

[0003] In such heat treatment facilities, a process gas suitable for each treatment is supplied into the treatment chamber. However, the gas nozzles for supplying the process gas are arranged in the peripheral part of the treatment chamber in order to avoid interference with the workpieces conveyed into the treatment chamber. The process gas supplied into the treatment chamber is sent to each part in the treatment chamber by a fan provided in the treatment chamber. However, since the gas flow by the fan follows the heat insulating wall forming the outer wall of the treatment chamber, it is difficult to spread the process gas to the central part of the treatment chamber (specifically, the workpiece located in the central part). For this reason, among a plurality of workpieces placed on a jig or the like and carried into the treatment chamber, there has been a problem that variations occur in the quality between the workpieces arranged on the outer side (position near the furnace wall) and the workpieces arranged on the inner side (position at the center of the treatment chamber). Such a problem is particularly likely to become apparent in surface treatments performed under a pressurized state.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Against the backdrop of the above circumstances, the present invention aims to provide a heat treatment system that can solve the problem of not being able to distribute the process gas supplied to the treatment chamber to the center of the treatment chamber. [Means for solving the problem]

[0006] Thus, the heat treatment equipment in the first aspect of this invention is defined as follows: A heat treatment apparatus that supplies a process gas into a processing chamber containing an item to be processed and performs heat treatment on the item to be processed, The process gas supply means for supplying the process gas into the processing chamber includes a first process gas supply means that supplies the process gas through a first nozzle fixedly arranged in the periphery of the processing chamber, and a second process gas supply means that supplies the process gas through a second nozzle that is movable relative to the processing chamber.

[0007] According to the heat treatment equipment in the first phase as defined above, when transporting a workpiece that may interfere with the workpiece, the second nozzle can be moved to a position where interference with the workpiece can be avoided. When supplying process gas into the treatment chamber, the second nozzle can be inserted to near the center of the treatment chamber. This allows the process gas to be supplied directly to the center of the treatment chamber through the second nozzle, separately from the first nozzle which is fixedly positioned around the periphery of the treatment chamber. In other words, the process gas can be distributed to the center of the treatment chamber.

[0008] Here, the second process gas supply means is A pre-chamber into which process gas supplied from the process gas source is introduced via a process gas supply line, The second nozzle has an elongated shape, with its base end positioned within the pre-chamber and its tip end positioned within the processing chamber, and supplies the process gas from the pre-chamber to the processing chamber. A moving device for moving the second nozzle in the axial direction of the nozzle, It can be configured to include the following (second phase). In this way, the second nozzle can be moved along the axial direction of the nozzle to a gas supply position for directly supplying process gas to the center of the processing chamber, and to a retracted position suitable for avoiding interference with the workpiece.

[0009] The heat treatment equipment in the third aspect of this invention is defined as follows: In the second phase, the system is equipped with a switching means for connecting either the process gas supply line or the vacuum exhaust line to the connection port of the pre-chamber. According to the heat treatment equipment of the third phase as defined in this manner, the second process gas supply means can be used as a local exhaust means to discharge harmful gases generated in the center of the treatment chamber to the outside of the chamber as needed.

[0010] The heat treatment equipment of the fourth aspect of this invention is defined as follows: In the second phase, within the pre-chamber, a first space into which the process gas is introduced, and a second space separated from the first space, are formed in the periphery of the pre-chamber. The second space has an opening that communicates with the inside of the furnace and is connected to a vacuum exhaust line, forming a path for vacuum exhaust. According to the heat treatment equipment of the fourth phase as defined in this way, the flow path for supplying process gas to the center of the treatment chamber and the flow path for vacuum exhaust to reduce the pressure inside the treatment chamber can be provided in substantially the same location, and the space around the furnace casing required for the installation of the second process gas supply means and vacuum exhaust line can be reduced.

[0011] The heat treatment equipment of the fifth aspect of this invention is defined as follows: In the first phase, the transport unit comprises (A) a batch-type heat treatment chamber arranged along a transport track, (B) a heat retention chamber for housing the workpieces to be treated and keeping them warm with a heater, and a transfer chamber for transferring the workpieces to be treated between the heat treatment chamber and the heat retention chamber. The second process gas supply means is provided in the heat treatment chamber together with the first process gas supply means. According to the heat treatment equipment of the fifth aspect defined as above, the problem that the process gas cannot be evenly distributed to the central part of the processing chamber in a batch-type heat treatment chamber can be satisfactorily solved.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram showing the overall configuration of the heat treatment equipment of an embodiment of the present invention. [Figure 2] It is a cross-sectional view showing the internal structure of the carburizing chamber and the transfer unit in the same embodiment. [Figure 3] It is a plan view of the carburizing chamber and the transfer unit. [Figure 4] It is a cross-sectional view showing the internal structure of the nitriding chamber in the same embodiment. [Figure 5] It is a diagram showing the supply lines and exhaust lines of various gases connected to the carburizing chamber and the nitriding chamber. [Figure 6] It is an operation explanatory diagram of the transfer mechanism in the same embodiment. [Figure 7] It is a diagram showing each step of the heat treatment in the same embodiment together with the heat pattern and pressure pattern for the workpiece to be processed. [Figure 8] It is a diagram showing a modified example in which a local exhaust function is added to the second process gas supply means. [Figure 9] It is a diagram showing a modified example in which a vacuum exhaust passage is provided inside the prechamber.

Embodiments for Carrying Out the Invention

[0013] Next, embodiments of the present invention will be described in detail below. FIG. 1 is a diagram showing the overall configuration of a heat treatment facility according to an embodiment of the present invention. In this figure, reference numeral 10 denotes a rail serving as a conveyance track linearly extending in the left-right direction in the figure. Along this rail 10, a plurality of batch-type processing chambers (here, carburizing chambers 12-1 and 12-2, a nitriding chamber 13, and a quenching chamber 14) are linearly arranged in a row in a state where an opening 44 (see FIG. 2) described later faces upward in the same direction in the figure. In this heat treatment facility 1, for example, as shown in FIG. 7, a carburizing treatment, a nitriding treatment, and a quenching treatment are performed on a work piece W.

[0014] On the right end side in FIG. 1, a loading table 16 is provided, and the work piece W from an upstream process is first placed on this loading table 16. The work piece W placed on the loading table 16 is carburized by the carburizing chambers 12-1 and 12-2, and then nitrided by the nitriding chamber 13. Subsequently, it is quenched in the quenching chamber 14, and then discharged to an extraction table 18 located on the left end side in the figure and at the lower side in the figure of the quenching chamber 14, and then carried out to a downstream process. Here, in this description, a plurality of work pieces that are integrally conveyed and heat-treated while being stacked in multiple stages on a jig are collectively referred to as the work piece W.

[0015] The heat treatment facility 1 of this embodiment has, in addition to the above-described carburizing chambers 12-1 and 12-2, nitriding chamber 13, and quenching chamber 14, a conveyance unit 20 that travels on the rail 10. The conveyance unit 20 receives the work piece W on the loading table 16, travels on the rail 10, and loads the work piece W into either of the carburizing chambers 12-1 and 12-2. Alternatively, the conveyance unit 20 receives the work piece W after being carburized in these carburizing chambers 12-1 and 12-2, travels on the rail 10, and loads it into the nitriding chamber 13. Further, the conveyance unit 20 receives the work piece W after nitriding treatment from the nitriding chamber 13, travels on the rail 10, and transfers it to the quenching chamber 14 to perform quenching treatment there.

[0016] Figure 2 shows the internal structure of the carburizing chamber 12-1 and the conveying unit 20. As shown in the figure, the carburizing chamber 12-1 has a bottomed cylindrical furnace shell 22 and an insulating material 24 placed inside it. The insulating material 24 constitutes a bottomed cylindrical insulating wall 25, and this insulating wall 25 forms a processing chamber 26 on its inside. The carburizing chamber 12-1 is equipped with suction ports 32 and 33. Suction port 32 is connected to the piping (vacuum piping) of the first vacuum exhaust line 162, which will be described later, and suction port 33 is connected to the vacuum piping of the second vacuum exhaust line 166 (see Figure 5). In addition, the nitrogen introduction line 146 is also connected to suction port 33, and suction port 33 also serves as a gas supply port for introducing pressurized nitrogen gas into the chamber.

[0017] The carburizing chamber 12-1 is also provided with a supply port 34 for supplying carburizing gas as a process gas. The carburizing gas supplied from the supply port 34 is first guided to a header 36, and then supplied to the inside of the carburizing chamber 12-1, specifically the processing chamber 26 inside the insulating wall 25, through a branch pipe 37 connected to the header 36 and a first nozzle 38 provided on the branch pipe 37. This first nozzle 38 is fixedly positioned around the processing chamber 26 (near the insulating wall 25) to avoid interference with the workpiece W being transported to the processing chamber 26. These header 36, branch pipe 37, and first nozzle 38 constitute the first process gas supply means 175. Although Figure 2 shows one first nozzle 38 on the branch pipe 37, multiple first nozzles 38 may be provided.

[0018] The insulating wall 25 is equipped with a fan 39 for stirring and circulating the gas supplied into the processing chamber 26, and a motor 40 for rotating the fan. Furthermore, a water-cooling panel 41 is provided near the motor 40 on the insulating wall 25 to protect the motor 40 from heat.

[0019] The carburizing chamber 12-1 is provided with a sliding door 42 that opens and closes the opening 44. The door 42 slides along the inner surface of the flange 48 by a cylinder 46, and in the closed state, it airtightly seals the opening 44 via a rubber packing. A plate-shaped insulating material 55 is provided on the door 42 in a manner that allows it to move integrally with the door, and this insulating material 55 closes the opening 52 of the cylindrical insulating wall 25. In the carburizing chamber 12-1, a water-cooling panel 51 is also provided on the inner surface of the door 42 to protect the rubber gasket that airtightly seals the opening 44 from heat.

[0020] The structure of the carburizing chamber 12-1 has been described above, but the other carburizing chambers 12-2 and nitriding chamber 13 have basically the same structure. For this reason, in the internal structure of the carburizing chamber 12-2 and nitriding chamber 13, parts that are the same as those in the carburizing chamber 12-1 are indicated only by symbols, and detailed explanations are omitted.

[0021] Figure 4 is a cross-sectional view showing the internal structure of the nitriding chamber in the same embodiment. In addition to the configuration described in the carburizing chamber 12-1, the nitriding chamber 13 is further provided with a mounting port 35 that communicates with the inside of the furnace (inside the chamber). The mounting port 35 is formed in the furnace shell 22 at a position overlooking the central part of the processing chamber 26, and a pre-chamber 177, which constitutes part of the second process gas supply means 176, is attached to the mounting port 35.

[0022] While the first process gas supply means 175 uses a fixed first nozzle 38 to supply process gas to the periphery of the processing chamber 26, the second process gas supply means 176 includes a pre-chamber 177, a second nozzle 182, and an air cylinder 185 as a moving device for moving the second nozzle 182, and supplies process gas (in this case, nitride gas) from a position closer to the center of the processing chamber 26 than the fixed first nozzle 38.

[0023] The pre-chamber 177 is a cylindrical member, with one end 178a connected to the mounting port 35 and the other end 178b to which an air cylinder 185 is attached. A process gas supply line 156 for supplying nitriding gas is connected to the connection port 179 of the pre-chamber 177, and the pressurized nitriding gas sent through the process gas supply line 156 is introduced into the interior of the pre-chamber 177.

[0024] The second nozzle 182 is an elongated tubular member whose base end is positioned inside the pre-chamber 177 and whose tip end is positioned inside the processing chamber 26. It is equipped with an inlet 182a on the base end, an internal flow path 182b extending in the axial direction, and a tip opening 182c, and is capable of supplying nitriding gas from the pre-chamber 177 into the processing chamber 26.

[0025] The second nozzle 182 is connected to the tip of a rod 186 that extends downward from the air cylinder 185, in a manner substantially coaxial with the rod 186. The rod-shaped member consisting of the rod 186 and the second nozzle 182 is arranged to pass through both ends of the pre-chamber 177. As shown in the enlarged section of the figure, both ends 178a and 178b of the pre-chamber 177 are composed of shaft flanges 181 with a sealing mechanism 180 housed inside, and the rod-shaped member consisting of a rod 186 and a second nozzle 182 that penetrates the pre-chamber 177 is supported by the shaft flanges 181 so as to be movable in the axial direction (up and down in this example).

[0026] Figure 4 shows the state in which the second nozzle 182 has moved to the gas supply position. In this state, the tip of the second nozzle 182 is located near the center of the processing chamber 26, and the nitriding gas in the pre-chamber 177 is supplied directly to the center of the processing chamber 26 through the second nozzle 182. Furthermore, the second nozzle 182 is movable upward from the gas supply position shown in Figure 4, so that interference with the workpiece W being transported can be avoided.

[0027] Figure 5 shows the supply and exhaust lines for various gases connected to the carburizing chambers 12-1, 12-2 and the nitriding chamber 13. As shown in the figure, process gas supply lines 149 are connected to the supply ports 34 of the carburizing chambers 12-1 and 12-2, respectively, to supply acetylene gas and nitrogen gas as carburizing gases into the chambers. The process gas supply line 149 includes a mass flow controller 150 for controlling the gas flow rate and on-off valves 151 and 152. The upstream side of the process gas supply line 149 is divided into branch pipes 149a and 149b. Branch pipe 149a is connected to piping 153a extending from the nitrogen gas supply source 153, and branch pipe 149b is connected to piping 154a extending from the acetylene gas supply source 154. With the process gas supply line 149 configured in this way, nitrogen gas and acetylene gas can be supplied into the carburizing chambers 12-1 and 12-2.

[0028] Meanwhile, a process gas supply line 156 for supplying ammonia gas as nitriding gas is connected to the supply port 34 of the nitriding chamber 13 and the pre-chamber 177. The process gas supply line 156 includes a mass flow controller 157 and an on-off valve 158 for controlling the gas flow rate, and the upstream side of the process gas supply line 156 is connected to a pipe 160a extending from an ammonia gas supply source 160. Nitrogen gas can also be supplied to the supply port 34 of the nitriding chamber 13 and the pre-chamber 177 via a pipe 159. Therefore, nitrogen gas and ammonia gas can be introduced into the nitriding chamber 13.

[0029] In addition, a nitrogen introduction line 146 is connected to the carburizing chambers 12-1, 12-2 and the nitriding chamber 13, separate from the process gas supply lines 149 and 156 mentioned above. One end of the nitrogen introduction line 146 is connected to the chamber's supply port 33, and the other end is connected to a pipe 153a extending from the nitrogen gas supply source 153, with an on / off valve 147 provided in its flow path. The nitrogen introduction line 146 is used to introduce nitrogen gas when pressurizing the inside of the chamber under reduced pressure.

[0030] The suction ports 32 of the carburizing chambers 12-1, 12-2 and the nitriding chamber 13 are each connected to a first vacuum exhaust line 162 for exhausting gas from inside the chambers. The first vacuum exhaust line 162 consists of a vacuum pump 163 and on-off valves 164 corresponding to each chamber, and the opening and closing of the on-off valves 164 connects and disconnects each processing chamber from the vacuum pump 163. In this example, by connecting the processing chamber to the vacuum pump 167, the inside of the chamber is maintained at a predetermined reduced pressure state (e.g., 1500 Pa).

[0031] Furthermore, the suction ports 33 of the carburizing chambers 12-1, 12-2 and the nitriding chamber 13 (the suction ports 33 also serve as gas supply ports when introducing nitrogen gas) are connected to a second vacuum exhaust line 166 for exhausting the gas inside the chambers. The second vacuum exhaust line 166 consists of a vacuum pump 167 and an on-off valve 168 corresponding to each chamber, and the opening and closing of the on-off valve 168 connects and disconnects each processing chamber from the vacuum pump 167. In this example, by connecting the processing chamber to the vacuum pump 167, the pressure inside the chamber is rapidly reduced from atmospheric pressure to a predetermined reduced pressure state.

[0032] In addition, in the nitriding chamber 13, a pressure adjustment line 172 is connected to the outlet 170 to maintain the pressure inside the chamber near atmospheric pressure during the nitriding process. The pressure adjustment line 172 consists of a pressure adjustment valve 173 and an on-off valve 174, and the pressure adjustment valve 173 adjusts the pressure inside the chamber to near atmospheric pressure, or more specifically, slightly higher than atmospheric pressure (for example, 105 kPa).

[0033] On the other hand, the quenching chamber 14 shown in Figure 1 has an oil cooling tank inside, and the workpiece W that has undergone nitriding treatment and been loaded by the transport unit 20 is immersed in the oil cooling tank to rapidly cool and perform quenching. This quenching chamber 14 has an opening 44 on the same side as the carburizing chambers 12-1, 12-2 and the nitriding chamber 13, i.e., on the upper side in Figure 1, and also has an opening 44 on the opposite side (lower side in the figure), and these openings 44 are opened and closed by sliding doors 42. 46 in Figure 1 is a cylinder that opens and closes the doors 42.

[0034] In Figure 2, the transport unit 20 has a traveling trolley 90 that runs on the rails 10, and further on the traveling trolley 90, there is a connecting trolley 92 that moves back and forth in the left-right direction in Figure 2, which is perpendicular to the rails 10, along with the transfer chamber 54, and connects and disconnects the transfer chamber 54 and the heating chamber 56 to the carburizing chambers 12-1, 12-2 and the nitriding chamber 13. 94 is a cylinder that moves the connecting trolley 92 forward and backward in a small stroke in the left-right direction in Figure 2, and the heat retention chamber 56 and the transfer chamber 54 are moved forward and backward in the left-right direction in Figure 2 by this cylinder 94, accompanied by the rolling of the roller 96. In this embodiment, these connecting trolleys 92, rollers 96, cylinders 94, etc., constitute the means for moving forward and backward.

[0035] The transport unit 20 has a transfer chamber 54 at the front end on the side of the carburizing chambers 12-1, 12-2 and the nitriding chamber 13, and a heat retention chamber 56 at the rear end on the opposite side for keeping the workpiece W warm during processes K2 and K4 in Figure 7.

[0036] The transfer chamber 54 has a pressure-resistant rectangular cylindrical wall 58, and a storage chamber 60 for accommodating the workpiece W to be processed is formed inside it. A transfer mechanism 62 is provided in this storage chamber 60. The transfer mechanism 62 transfers the workpiece W between the carburizing chambers 12-1 and 12-2 and the rear heat retention chamber 56. As shown in Figure 6, it has a fork section 62A and horizontal sliding members 62B and 62C, and the workpiece W is transferred at the fork section 62A by sliding them horizontally.

[0037] The transfer chamber 54 is provided with a suction port 63, which is connected to the vacuum pump 64 shown in Figure 3 via a suction pipe 66A, so that the inside of the transfer chamber 54 is vacuum-suctioned by the vacuum pump 64. An on-off valve 68A, which consists of a solenoid valve, is provided on the suction pipe 66, and the suction port 63 and the vacuum pump 64 are connected and disconnected by opening and closing the on-off valve 68A.

[0038] The transfer chamber 54 is also provided with a supply port 70, as shown in Figure 3, through which nitrogen gas is supplied into the transfer chamber 54. The transfer chamber 54 has an opening 72 at its front end, i.e., the left end in Figure 2, which does not have a door. The transfer chamber 54 is provided with a flat, frame-shaped packing 74 around this opening 72. The transfer chamber 54 is docked with the carburizing chambers 12-1, 12-2 and nitriding chamber 13 by moving forward toward the carburizing chambers 12-1, 12-2 and nitriding chamber 13, with the frame-shaped packing 74 in airtight contact with the outer surfaces of the carburizing chambers 12-1, 12-2 and nitriding chamber 13.

[0039] On the other hand, the latter heating chamber 56 has an insulating material 78 inside a bottomed cylindrical furnace shell 76, and this insulating material 78 constitutes an insulating wall 80. The insulating wall 80 forms a containment chamber 82 on its inside, where the workpiece W to be processed is housed. A support frame 84 is provided in the containment chamber 82, and the workpiece W to be processed in the containment chamber 82 is placed on and supported by the support frame 84.

[0040] As shown in Figure 3, the insulated chamber 56 is provided with a suction port 86 for vacuuming its interior, and this suction port 86 is connected to the vacuum pump 64 via a suction pipe 66B. An on-off valve 68B, which is made of an electromagnetic valve, is provided on this suction pipe 66B, and the opening and closing operation of the on-off valve 68B connects and disconnects the suction port 86 and the vacuum pump 64.

[0041] As shown in Figure 2, the heat-insulating chamber 56 has a heater 120 inside the insulating wall 80 for keeping the workpiece W warm. The heat-insulating chamber 56 is also provided with insulating doors 110 and 112 that open and close the upper opening 104 and lower opening 106 of the insulating wall 80, and these doors are opened and closed by cylinders 114 and 116.

[0042] The heating chamber 56 also has a supply port (not shown) in the furnace shell 76 for supplying nitrogen gas to the interior as a cooling gas. Furthermore, the device includes a heat exchanger (not shown) that lowers the temperature of supplied nitrogen gas by passing it through water-cooling pipes through heat exchange, a cooling fan 100 that agitates the cooled nitrogen gas and circulates it within the heat-insulating chamber 56, and a motor 102 that rotates the fan. These components constitute a gas cooling device for the workpiece W.

[0043] In this gas cooling system, the rotation of the cooling fan 100 causes the temperature of nitrogen gas to decrease, which then flows upward through the opening 106 at the bottom of the insulated wall 80, hitting the workpiece W. After cooling, the nitrogen gas flows out through the opening 104 at the top of the insulated wall 80, passes through the heat exchanger 98 again, and is further cooled there. The workpiece W is then cooled while this circulating flow is maintained.

[0044] In other words, in this embodiment, the heat retention chamber 56 is equipped with a cooling function in addition to a heat retention function for keeping the workpiece W warm.

[0045] As shown in Figure 2, an opening 122 is provided between the heat retention chamber 56 and the transfer chamber 54, specifically at the end of the heat retention chamber 56 on the transfer chamber 54 side. This opening 122 is opened and closed by a door 128 that slides along the inner surface of the flange 126 by a cylinder 124.

[0046] Similar to the carburizing chamber 12-1 described above, the door 128 of this heat-insulating chamber 56 is also provided with a plate-shaped insulating material 130 that moves integrally with the opening 129 of the insulating wall 80, and a water-cooling panel 132 is provided on the door 128 to protect the rubber gasket that airtightly seals the opening 122 from heat.

[0047] Next, a series of heat treatments in this embodiment will be described. In the following description, it will be assumed that the series of heat treatments are carried out according to the steps shown in Figure 7. First, the transport unit 20 receives the workpiece W on the loading table 16 via the transfer mechanism 62 and places it into the transfer chamber 54. Then, the transport unit 20 moves to one of the carburizing chambers, in this case carburizing chamber 12-1, and transports the workpiece W.

[0048] Subsequently, the transfer unit 20 uses the cylinder 94 to move the transfer chamber 54 forward a small distance towards the carburizing chamber 12-2 side together with the rear heat retention chamber 56, docking the transfer chamber 54 with the carburizing chamber 12-1 so that the frame-shaped packing 74 at the tip of the transfer chamber 54 is in close contact with the outer surface of the carburizing chamber 12-1.

[0049] Then, with the door 128 between the transfer chamber 54 and the heat-insulating chamber 56 closed, the inside of the transfer chamber 54 is vacuum-suctioned through the suction port 63 by the vacuum pump 64, and the pressure inside the transfer chamber 54 is reduced to a vacuum pressure similar to that of the carburizing chamber 12-1.

[0050] When the pressure inside the transfer chamber 54 becomes a vacuum pressure similar to the pressure inside the carburizing chamber 12-1, the door 42 of the carburizing chamber 12-1 is opened, and the workpiece W to be processed in the transfer chamber 54 is loaded into the processing chamber 26 inside the carburizing chamber 12-1 by the transfer mechanism 62 and set on the stand 30.

[0051] When the product to be treated W is placed inside the carburizing chamber 12-1, heating of the product to be treated W is started and the temperature is raised to the carburizing temperature of 930°C.

[0052] To accelerate the temperature rise, nitrogen gas is supplied into the carburizing chamber 12-1 from the supply port 34, and a fan 39 is rotated. The convective heating from the fan 39 and the radiant heat from the heater 28 quickly raise the temperature of the workpiece W to the carburizing temperature of 930°C.

[0053] When the workpiece W has been heated to the carburizing temperature of 930°C, the nitrogen gas inside the carburizing chamber 12-1 is evacuated through the suction port 33, and the pressure inside the carburizing chamber 12-1 is reduced to the set vacuum pressure (1500 Pa). Subsequently, the supply gas to the carburizing chamber 12-1 via the supply port 34 is switched from nitrogen gas to carburizing gas, and carburizing is performed on the product W to be processed. At this time, the carburizing gas (acetylene gas) supplied to the carburizing chamber 12-1 is supplied in an amount determined in advance by simulation, and at a predetermined time. Subsequently, with the supply of carburizing gas stopped, the workpiece W is maintained at a temperature of 930°C, and the C atoms that have entered the workpiece W are diffused.

[0054] Once the carburizing treatment of the workpiece W is completed in this manner, the transport unit 20, which had temporarily moved away from the carburizing chamber 12-1, is moved forward again toward the carburizing chamber 12-1, and the transfer chamber 54 is docked with the carburizing chamber 12-1. Then, with the door 128 between the transfer chamber 54 and the heat retention chamber 56 open, the inside of the transfer chamber 54 and the inside of the heat retention chamber 56 are evacuated using the vacuum pump 64 to create a vacuum pressure.

[0055] Subsequently, the door 42 of the carburizing chamber 12-1 is opened, and the carburized workpiece W inside the carburizing chamber 12-1 is moved into the transfer chamber 54. Then, it is moved from the transfer chamber 54 to the heat retention chamber 56, where the workpiece W is placed.

[0056] Once the workpiece W is placed inside the heating chamber 56, the door 128 is closed, and then the workpiece W is heated to the desired temperature (850°C) inside the heating chamber 56 using the heater 120. Alternatively, a gas cooling device can be used to forcibly cool the workpiece W to the desired temperature (850°C).

[0057] The transport unit 20 maintains the temperature of the workpiece W even while it is moving away from the carburizing chamber 12-1. When the pressure in the transfer chamber 54 and the pressure in the nitriding chamber 13 reach approximately the same vacuum pressure, the workpiece W, which has been maintained at the target temperature, is then loaded into the nitriding chamber 13 through the transfer chamber 54. At this time, the second nozzle 182 in the nitriding chamber 13 is retracted upward to avoid interference with the workpiece W.

[0058] The workpiece W, which is placed in the nitriding chamber 13, is then subjected to nitriding treatment inside the nitriding chamber 13 while being maintained at the nitriding temperature of 850°C. In detail, with the door 42 (see Figure 4) of the nitriding chamber 13 closed, the workpiece W is heated by the heater 28 to maintain a nitriding temperature of 850°C. Meanwhile, nitrogen gas is introduced into the processing chamber 26 through the supply port 33, and the processing chamber 26 is pressurized (re-pressurized). After re-pressurization, nitriding gas containing ammonia is supplied into the processing chamber 26. In this embodiment, nitriding gas is supplied from the first nozzle 38 which is fixedly positioned around the periphery of the processing chamber 26, and the second nozzle 182 is inserted to near the center of the processing chamber 26. Nitriding gas is supplied directly to the center of the processing chamber 26 through the second nozzle 182, allowing the nitriding gas to spread throughout the center of the processing chamber 26. During the nitriding process, the flow rate of nitriding gas supplied into the processing chamber 26 is controlled by quantitative control and feedback control. The processing chamber 26 is also maintained at a predetermined nitriding pressure (in this case, 105 kPa, slightly higher than atmospheric pressure) by a pressure adjustment line 172.

[0059] Once the nitriding process is complete, the gas inside the nitriding chamber 13 is evacuated through the suction port 33, and when the vacuum pressure inside the nitriding chamber 13 is approximately the same as the pressure inside the transfer chamber 54, the transfer chamber 54 is docked to the nitriding chamber 13. Then the nitrided workpiece W is removed from the nitriding chamber 13 (at this time, the second nozzle 182 is moved upward to avoid interference with the workpiece W), and the workpiece W is placed in the heat retention chamber 56 and kept at the target temperature (850°C).

[0060] Next, the transport unit 20 moves to the left in Figure 1, bringing the nitrided workpiece W to the front of the quenching chamber 14, and then loading it into the quenching chamber 14.

[0061] At this time, in the transport unit 20, after docking the transfer chamber 54 with the quenching chamber 14, the inside of the transfer chamber 54 is first vacuumed with the door 128 closed, and then nitrogen gas is supplied into the transfer chamber 54 through the supply port 70 to bring the inside to atmospheric pressure.

[0062] Next, the vacuum suction inside the heating chamber 56 is stopped, and nitrogen gas is supplied to it through the supply port 88 to bring the inside to atmospheric pressure. In this state, the door 128 and the door 42 on the quenching chamber 14 side are opened, and the carburized and nitrided workpiece W inside the heating chamber 56 is loaded into the quenching chamber 14 via the transfer chamber 54. In this example, the transfer of the workpiece W from the heat-insulating chamber 56 to the quenching chamber 14 is shown under atmospheric pressure. However, it is also possible to transfer the workpiece W under other predetermined pressures (for example, under vacuum).

[0063] The quenching chamber 14, upon receiving the workpiece W, immerses it in an oil-cooling tank located inside to rapidly cool and quench it. The quenched workpiece W is then discharged through an opening 44 on the opposite side of the rail 10 of the quenching chamber 14 to the extraction table 18 shown at the bottom of Figure 1. The workpiece W discharged onto the extraction table 18 is then taken down to the downstream process.

[0064] According to the heat treatment equipment 1 of this embodiment, configured as described above, the nitriding chamber 13 is provided with a second process gas supply means 176 including a second nozzle 182 that is movable relative to the processing chamber 26. During nitriding, the second nozzle 182 can be inserted to near the center of the processing chamber 26, and nitriding gas can be supplied directly to the center of the processing chamber 26 through the second nozzle 182, separately from the first nozzle 38 which is fixedly positioned around the periphery of the processing chamber 26. In other words, during nitriding, the nitriding gas can be distributed to the center of the processing chamber 26.

[0065] Furthermore, in the heat treatment equipment 1 of this embodiment, the second process gas supply means 176 includes a pre-chamber 177 into which process gas is introduced, an elongated second nozzle 182 that can be positioned with its base end inside the pre-chamber 177 and its tip end inside the processing chamber 26, and an air cylinder 185 for moving the second nozzle 182. The second nozzle 182 can be moved along the axial direction of the nozzle to a gas supply position for directly supplying nitriding gas to the center of the processing chamber 26 and to a retracted position suitable for avoiding interference with the workpiece W to be processed.

[0066] Next, Figure 8 shows a modified example in which a local exhaust function is added to the second process gas supply means 176 of the nitriding chamber 13. In the example shown in Figure 8, a process gas supply line 156 is connected to the connection port 179 of the pre-chamber 177, which constitutes the second process gas supply means 176, via an on-off valve 190, and a vacuum exhaust line 192 equipped with a vacuum pump 191 is connected via an on-off valve 193. These on-off valves 190 and 193 constitute a switching means 195 that connects either the process gas supply line 156 or the vacuum exhaust line 192 to the connection port 179.

[0067] In the example shown in Figure 8, by switching the switching means 195, it is possible to selectively switch between a first state in which the process gas supply line 156 and the pre-chamber 177 are connected to allow the supply of nitride gas into the processing chamber 26, and a second state in which the vacuum exhaust line 192 and the pre-chamber 177 are connected to allow the exhaust of the processing chamber 26. For example, if harmful gases are generated from the workpiece W during the heat treatment, the system can be switched to the second state, and the second process gas supply means 176 can be used as a local exhaust means to suck the gas near the center of the processing chamber 26 through the tip opening 182c of the nozzle 182 and discharge it outside the chamber.

[0068] Figure 9 shows a modified example in which a vacuum evacuation channel is provided inside the pre-chamber. In the example shown in Figure 9, the pre-chamber 177 attached to the mounting port 35 has a first space 200 into which process gas is introduced, as well as a second space 201 separated from the first space 200. The second space 201 formed around the pre-chamber 177 has an opening 202 at the shaft flange 181 of one end 178a that communicates with the inside of the furnace, and is connected to the first vacuum exhaust line 162 via a connection port 203. The second space 201 constitutes a vacuum exhaust path when exhausting gas from inside the processing chamber 26.

[0069] In the example shown in Figure 9, which is configured in this way, in a nitriding chamber 13 equipped with a second process gas supply means 176 and a vacuum exhaust line 162, the flow paths 200 and 182b for supplying process gas to the central part of the processing chamber 26 and the flow path 201 for vacuum exhaust to reduce the pressure inside the processing chamber 26 can be provided in substantially the same location, thereby reducing the space around the furnace casing required for the installation of the second process gas supply means 176 and the vacuum exhaust line 162.

[0070] Although embodiments and modifications of the present invention have been described in detail above, these are merely examples. For example, the above embodiment employs a configuration in which the second nozzle moves in the vertical direction, but it is also possible to adopt a direction other than vertical (for example, the horizontal direction) as the direction of movement of the second nozzle. Furthermore, although the above embodiment was an example in which a second process gas supply means was provided in a nitriding chamber among several batch-type processing chambers, it is also possible to provide a second process gas supply means in a carburizing chamber other than a nitriding chamber. In addition, it is also possible to provide a second process gas supply means in a continuous heat treatment facility in which multiple processing chambers are connected in series along the conveying direction, and so on. The present invention can be configured in various modified forms without departing from its spirit. [Explanation of Symbols]

[0071] 1. Heat treatment equipment 10 rails 12. Carburizing Chamber (Heat Treatment Chamber) 13. Nitriding Chamber (Heat Treatment Chamber) 20 Conveyor Units 26 Processing Room 36 Header 37 Branch pipe 38. Nozzle No. 1 54 Transfer Chamber 56 Insulation Chamber 149,156 Process gas supply lines 160 Ammonia gas supply source (process gas supply source) 162 First vacuum exhaust line 175 First process gas supply means 176 Second process gas supply means 177 Pre-chamber 179 connection ports 185 Air Cylinder (Moving Device) 190,193 Shut-off valves 192 Vacuum exhaust line 195 Switching means 200 1st space 201 2nd space 202 Aperture W - Items to be processed

Claims

1. A heat treatment apparatus that supplies a process gas into a processing chamber containing an item to be processed and performs heat treatment on the item to be processed, A heat treatment facility comprising, as a process gas supply means for supplying the process gas into the processing chamber, a first process gas supply means that supplies the process gas through a first nozzle fixedly arranged in the periphery of the processing chamber, and a second process gas supply means that supplies the process gas through a second nozzle that is movable relative to the processing chamber.

2. The second process gas supply means is A pre-chamber into which process gas supplied from the process gas source is introduced via a process gas supply line, The second nozzle has an elongated shape, with its base end positioned within the pre-chamber and its tip end positioned within the processing chamber, and supplies the process gas from the pre-chamber to the processing chamber. A moving device for moving the second nozzle in the axial direction of the nozzle, The heat treatment apparatus according to claim 1, comprising:

3. The heat treatment apparatus according to claim 2, further comprising a switching means for connecting either the process gas supply line or the vacuum exhaust line to the connection port of the pre-chamber.

4. Inside the pre-chamber, a first space into which the process gas is introduced, and a second space separated from the first space, are formed in the peripheral area of ​​the pre-chamber. The heat treatment apparatus according to claim 2, wherein the second space has an opening that communicates with the inside of the furnace and is connected to a vacuum exhaust line to constitute a flow path for vacuum exhaust.

5. (A) Batch-type heat treatment chambers arranged along a transport track, (B) A transport unit comprising a heating chamber for housing the workpiece to be processed and keeping it warm with a heater, and a transfer chamber for transferring the workpiece to be processed between the heat treatment chamber and the heating chamber, It has, The heat treatment apparatus according to claim 1, wherein the heat treatment chamber is provided with the second process gas supply means together with the first process gas supply means.

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