Heat treatment facility

Abstract

To provide a heat treatment facility capable of shortening the time required for heat treatment of a workpiece.SOLUTION: A heat treatment facility 1 includes a vacuum chamber 2, a plurality of first heating chambers 3 and a plurality of second heating chambers 4 which are respectively arranged in parallel inside the vacuum chamber 2, a cooling chamber 6 which accommodates a workpiece W and cools the workpiece W by a cooling gas, and a workpiece conveyance mechanism 5 which is provided inside the vacuum chamber 2 and delivers the workpiece W between the first heating chamber 3, the second heating chamber 4, and the cooling chamber 6. The first heating chamber 3 has a first heater 17 as heating means, and the second heating chamber 4 has a second heater 27 as heating means and a water-cooled panel 30 as cooling means.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a heat treatment facility for heat-treating a metal workpiece.

Background Art

[0002] Conventionally, in steel component materials, isothermal annealing has been carried out for the purpose of improving machinability in subsequent processes. In isothermal annealing, a primary heating process for once transforming steel into an austenite structure, an intermediate cooling process for cooling to the target temperature in a relatively short time thereafter, and a soaking process for soaking at the target temperature are carried out. When carrying out such isothermal annealing, it has generally been common to use a continuous atmosphere heat treatment furnace in which three chambers, namely a primary furnace responsible for the primary heating process, a quenching chamber responsible for the intermediate cooling process, and a secondary furnace responsible for the soaking process, are connected in series in this order (see, for example, Patent Document 1 below).

[0003] Here, in isothermal annealing, control of the cooling rate in the quenching chamber (intermediate cooling process) and the holding temperature in the secondary furnace are important, but the optimal heat treatment conditions that can finish isothermal transformation at the fastest speed vary depending on the steel type. For this reason, when processing different steel types, it is desirable to appropriately change the heat treatment conditions (for example, the temperature and holding time during soaking) according to the steel type. However, in a continuous atmosphere heat treatment furnace as described above, it is difficult to change the heat treatment conditions in accordance with the switching of steel types, and there has been a problem that the holding time in the secondary furnace becomes significantly longer than the theoretically fastest transformation time, resulting in deteriorated productivity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention is based on the above circumstances, and an object thereof is to provide a heat treatment facility capable of shortening the time required for heat treatment of a workpiece to be processed.

Means for Solving the Problems

[0006] And the heat treatment facility according to the first aspect of the present invention is defined as follows. That is, A heat treatment facility for performing heat treatment on a metal workpiece, A vacuum chamber, A plurality of first heating chambers and a plurality of second heating chambers arranged in parallel inside the vacuum chamber, A cooling chamber for accommodating the workpiece to be processed and cooling the workpiece with a cooling gas, A workpiece transfer mechanism provided inside the vacuum chamber for transferring the workpiece between the first heating chamber, the second heating chamber, and the cooling chamber, Comprising, The first heating chamber has a first heater as a heating means, The second heating chamber has a second heater as a heating means and a water-cooled panel as a cooling means.

[0007] In the heat treatment facility according to the first aspect defined in this way, a plurality of first heating chambers and a plurality of second heating chambers are arranged in parallel inside the vacuum chamber, and heat treatment with different heat patterns can be performed for each heating chamber in the vacuum chamber. For this reason, even when heat-treating workpieces with different optimal heat patterns at the same time, it is possible to realize the optimal heat pattern corresponding to each workpiece for each heating chamber, and the heat treatment can be completed for each workpiece in the theoretically fastest transformation time or a time close thereto. Further, in this heat treatment facility, since a series of processes from primary heating, intermediate cooling, to soaking are performed in a vacuum state, there is no need to perform pressure change operations such as repressurization and subsequent depressurization in the process of transitioning to each step of primary heating, intermediate cooling, and soaking, and the time required for a series of heat treatments can be shortened.

[0008] Here, the second heating chamber can be provided with the water-cooled panel on the side opposite to the workpiece with respect to the second heater, and a shutter mechanism can be provided between the second heater and the water-cooled panel (second aspect). In this way, by closing the shutter provided between the second heater and the water-cooled panel at the end of the intermediate cooling in isothermal annealing, the cooling gradient near the target soaking temperature can be relaxed, and the undershoot with respect to the target soaking temperature can be reduced. Further, by closing the shutter, the water-cooled panel arranged close to the second heater can be protected from the radiant heat of the second heater.

[0009] Further, in this heat treatment facility, in the second heating chamber, by providing the second heater, the water-cooled panel, and the shutter mechanism on the upper side and the lower side in the vertical direction with the workpiece sandwiched therebetween, the workpiece accommodated inside can be heat-treated uniformly from the upper and lower two directions (third aspect).

[0010] Further, in this heat treatment facility, in the second heating chamber, it can be configured to include a radiation thermometer for measuring the temperature of the workpiece accommodated inside (fourth aspect). In this way, temperature control can be performed based on the temperature of the workpiece measured by the radiation thermometer.

Brief Description of the Drawings

[0011]

Figure 1

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Embodiments for Carrying out the Invention

[0012] Next, embodiments of the present invention will be described in detail below. FIG. 1 shows a schematic overall configuration of a heat treatment equipment according to an embodiment of the present invention. In the figure, 1 is a heat treatment equipment for performing a series of heat treatments on a workpiece W such as a steel part material. The heat treatment equipment 1 includes a box-shaped steel vacuum chamber 2. The vacuum chamber 2 has pressure resistance and its interior can be depressurized to a predetermined degree of vacuum. Inside the vacuum chamber 2, first heating chambers 3A, 3B, 3C and second heating chambers 4A, 4B, 4C arranged along the vertical direction are provided, and further a workpiece transfer mechanism 5 for transferring the workpiece W while moving along the vertical direction is provided.

[0013] In addition, a cooling chamber 6 and a temporary placement chamber 7 are attached to the side wall of the vacuum chamber 2 on the side opposite to the first heating chambers 3A, 3B, 3C and the second heating chambers 4A, 4B, 4C with the workpiece transfer mechanism 5 interposed therebetween. In the following, when referring to the first heating chambers 3A, 3B, 3C collectively, they may be referred to as "first heating chamber 3". Also, when referring to the second heating chambers 4A, 4B, 4C collectively, they may be referred to as "second heating chamber 4".

[0014] FIG. 3 is a diagram showing a schematic configuration of the first heating chamber 3A. The first heating chamber 3A is a section for heating the workpiece W to a predetermined temperature (for example, 900° C.) under a vacuum atmosphere. The first heating chamber 3A has a heat-resistant heat insulating material, and the heat insulating material forms a box-shaped heat insulating wall 11. A side wall 11a (see FIG. 3(A)) of the heat insulating wall 11 facing the workpiece transfer mechanism 5 is an opening / closing door that opens and closes when transferring the workpiece W, and is configured to be rotatable around a shaft 14 of an opening / closing device 13. Inside the heat insulating wall 11, a rack member 15 for holding the workpiece W and a first heater 17 as heating means are provided. The first heater 17 is disposed above and below the workpiece W.

[0015] One end of a vacuum exhaust pipe 19 extending from a vacuum pump 18 (see FIG. 1) is connected to the first heating chamber 3A, and the inside of the first heating chamber 3A and further the inside of the vacuum chamber 2 can be decompressed to a predetermined degree of vacuum. As described above for the first heating chamber 3A, the other first heating chambers 3B and 3C have the same configuration.

[0016] FIG. 4 is a diagram showing a schematic configuration of the second heating chamber 4A. The second heating chamber 4A is a section for cooling the workpiece W heated in any one of the first heating chambers 3A, 3B, and 3C to a target temperature (for example, 600° C.) under a vacuum atmosphere, and then holding the workpiece W at such a target temperature. The second heating chamber 4A has a heat-resistant heat insulating material as in the first heating chambers 3A, 3B, and 3C, and the heat insulating material forms a box-shaped heat insulating wall 21. A side wall 21a (see FIG. 4(A)) of the heat insulating wall 21 facing the workpiece transfer mechanism 5 is an opening / closing door that opens and closes when transferring the workpiece W, and is configured to be rotatable around a shaft 24 of an opening / closing device 23. Inside the heat insulating wall 21, a rack member 25 for holding the workpiece W and a second heater 27 as heating means are provided. The second heater 27 is disposed above and below the workpiece W.

[0017] One end of a vacuum exhaust pipe 19 extending from a vacuum pump 18 (see Fig. 1) is connected to the second heating chamber 4A, and the inside of the second heating chamber 4A and further the inside of the vacuum chamber 2 can be decompressed to a predetermined degree of vacuum.

[0018] In the second heating chamber 4A, a water-cooled panel 30 is provided as cooling means for cooling the workpiece W in a vacuum atmosphere. Openings 31 and 32 are respectively provided in the upper and lower parts of the heat insulating wall 21 in the second heating chamber 4A. Through these openings 31 and 32, the water-cooled panel 30 is disposed above the opening 31 and below the opening 32 so as to face the upper and lower surfaces of the workpiece W respectively. The water-cooled panel 30 has a cooling water flow path formed therein for circulating cooling water. By circulating cooling water inside the water-cooled panel 30, the heat generated from the high-temperature workpiece W is recovered.

[0019] As shown in Fig. 4(B), a shutter mechanism 40 is provided between the second heater 27 and the water-cooled panel 30. The shutter mechanism 40 includes a heat insulating plate 41 made of a heat insulating material for opening and closing the opening 31 or 32, and a cylinder device 43 for operating the heat insulating plate 41 to open and close. The heat insulating plate 41 is composed of halves 41a and 41b, and the openings 31 or 32 are opened by moving these halves 41a and 41b in opposite directions from near the center of the opening 31 or 32 respectively. Fig. 5 shows a state where the shutter mechanism 40 has opened the openings 31 and 32. In this example, the heat insulating plate 41 is made of a heat insulating material, but it is also possible to configure the heat insulating plate 41 with a reflection plate made of metal that reflects radiant heat.

[0020] A pair of shutter mechanisms 40, 40 provided respectively above and below open the openings 31, 32 when cooling the workpiece W, enabling radiative cooling of the workpiece W by the water-cooled panel 30. On the other hand, when maintaining the workpiece W at a constant temperature by the second heater 27, the openings 31, 32 are closed with the heat insulating plate 41 to prevent damage to the water-cooled panel 30 by the heat from the second heater 27.

[0021] In this second heating chamber 4A, as shown in Fig. 4(A), a radiation thermometer 50 for measuring the temperature of the workpiece W accommodated therein is provided. In the heat treatment facility 1 of the present embodiment, based on the temperature of the workpiece W measured by the radiation thermometer 50, the opening / closing operation of the shutter mechanism 40 and the like are controlled. The radiation thermometer 50 is accommodated in a carbon housing tube 51 that penetrates the side wall of the heat insulation wall 21. A window portion (not shown) made of heat-resistant glass is provided at the tip of the housing tube 51, and the radiation thermometer 50 is configured to be able to measure the temperature of the workpiece W through the window portion. The output signal from the radiation thermometer 50 is output toward a control unit (not shown) that controls the operation of the heat treatment facility 1. As described above, the configuration of the second heating chamber 4A has been explained, but the other second heating chambers 4B and 4C have the same configuration.

[0022] Next, the cooling chamber 6 and the temporary placement chamber 7 will be described. The cooling chamber 6 shown in Fig. 1 is a section for cooling the workpiece W that has been rapidly cooled and isothermally held in the vacuum chamber 2 to a temperature at which it can be taken out. It is also the section that first receives the workpiece W conveyed from the upstream process. The cooling chamber 6 has a pressure-resistant housing portion 60 attached to the opening 2a portion of the vacuum chamber 2. The housing portion 60 is formed with an outer opening 61 for loading the workpiece W from the upstream process and an inner opening 62 formed at a position facing the outer opening 61 and communicating with the vacuum chamber 2. Openable doors 63 and 64 are provided at these openings 61 and 62, respectively. The door 63 is capable of hermetically closing the outer opening 61, and the door 64 is capable of hermetically closing the inner opening 62. Inside the cooling chamber 6, a rack member 65 for holding the loaded workpiece W is provided.

[0023] Connected to this cooling chamber 6 are a vacuum exhaust pipe 68 extending from a vacuum pump 67 and a pipe 69 for supplying N2 gas connected to an N2 gas source (not shown). Above the cooling chamber 6, a gas cooling unit 70 equipped with a gas cooler 71 and a fan 72 for circulating the cooling gas is provided. An opening (mesh-shaped opening), not shown in the figure, is provided in the housing portion 60 of the cooling chamber 6 that comes into contact with the gas cooling unit 70, and the gas cooling unit 70 and the cooling chamber 6 are configured to communicate with each other through the opening. By circulating the cooling gas (N2 gas) between the gas cooling unit 70 and the cooling chamber 6, it is possible to cool the workpiece W accommodated inside the cooling chamber 6. When the cooling chamber 6 is evacuated, not only the cooling chamber 6 but also the gas cooling unit 70 is depressurized together.

[0024] As shown in FIG. 1, a temporary placement chamber 7 is provided below the cooling chamber 6. The temporary placement chamber 7 is a compartment for temporarily placing the workpiece W loaded into the interior of the vacuum chamber 2 from the upstream process. The temporary placement chamber 7 includes a pressure-resistant housing portion 75 attached to the opening 2b portion of the vacuum chamber 2, and an inner opening 76 communicating with the interior of the vacuum chamber 2 is formed. Inside the temporary placement chamber 7, a rack member 77 for holding the loaded workpiece W is provided.

[0025] Next, the workpiece transfer mechanism 5 will be described. As shown in FIG. 1, the workpiece transfer mechanism 5 is provided between a group of heating chambers 3 and 4 arranged in a row on the left side in the figure and the cooling chamber 6 and the temporary placement chamber 7 arranged on the right side in the figure. The workpiece transfer mechanism 5 includes a platform 80 supported to be movable in the vertical direction by guide rails (not shown), chains 81 and 82 for moving the platform 80 in the vertical direction, and forks 85 and 86 disposed on the platform 80 and extendable and retractable in the horizontal direction.

[0026] In this embodiment, for example, as shown in FIG. 6, a plurality of workpieces W made of a steel part material or the like are conveyed in a state of being arranged flat on a lattice-shaped tray t. In this case, the tray t and the workpiece W are placed on the fork 85 as shown in the figure. When transferring the workpiece W, the workpiece transfer mechanism 5 raises and lowers the platform 80 to a position facing the first heating chamber 3 or the second heating chamber 4 on the receiving side, and then extends the forks 85 and 86 in the horizontal direction to insert the tray t with the workpiece W into the first heating chamber 3 or the second heating chamber 4. Also, the tray t with the workpiece W after processing is taken out from the heating chamber 3 or the second heating chamber 4. The forks 85 and 86 can also be extended into the cooling chamber 6 and the temporary storage chamber 7 located on the side opposite to the heating chambers 3 and 4. By using the workpiece transfer mechanism 5 configured in this way, the workpiece W held in the temporary storage chamber 7 is conveyed to any one of the plurality of first heating chambers 3A, 3B, and 3C selected, processed in the first heating chamber, then conveyed to any one of the plurality of second heating chambers 4A, 4B, and 4C selected, and after being processed in the second heating chamber, conveyed to the cooling chamber 6. Note that the configuration of such a workpiece transfer mechanism 5 is described, for example, in Japanese Patent Publication No. 2013-504686.

[0027] The various operations in each of the processing chambers 3, 4, 6, 7 and the workpiece transfer mechanism 5 described above are controlled by a control unit (not shown) of the heat treatment facility 1. The control unit stores in advance the optimal heat patterns for each workpiece with a different steel type, and each of the first heating chambers 3A, 3B, 3C and the second heating chambers 4A, 4B, 4C can control its furnace temperature, holding time, etc. based on the optimal heat pattern for the workpiece W to be charged.

[0028] Next, taking the case of performing isothermal annealing shown in FIG. 7 as an example, a series of heat treatment operations in the heat treatment facility 1 will be described. Hereinafter, the operation of the heat treatment facility 1 will be mainly described by paying attention to the workpiece W hatched in the time chart of FIG. 8.

[0029] First, when the workpiece W sent from the upstream process is loaded into the cooling chamber 6 through the opening 61, in the cooling chamber 6, the door 63 is closed and the inside is depressurized using the vacuum pump 67, and the air inside the cooling chamber 6 is discharged to the outside of the room. When the inside of the cooling chamber 6 is depressurized to about the same level as the inside of the vacuum chamber 2 and the door 64 opens, the workpiece transfer mechanism 5 receives the workpiece W in the cooling chamber 6. Subsequently, the workpiece transfer mechanism 5 conveys the workpiece W to the position of the temporary placement chamber 7 and temporarily loads the workpiece W into the temporary placement chamber 7.

[0030] After that, the workpiece transfer mechanism 5 receives the workpiece W in the temporary placement chamber 7 and conveys the workpiece W to the position of any one of the first heating chambers 3 (here, the first heating chamber 3A). Then, the workpiece W is loaded into the first heating chamber 3A and set on the rack member 15. When the workpiece W is loaded, in the first heating chamber 3A, under a vacuum atmosphere, heating of the workpiece W is started by radiant heating from the first heater 17, and the workpiece W is heated up to the target heating temperature (here, 900 °C) (primary heating step K1 in FIG. 7).

[0031] After the heat treatment in the first heating chamber 3A is completed, the workpiece transfer mechanism 5 receives the workpiece W in the first heating chamber 3A and conveys the workpiece W to the position of any one of the second heating chambers 4 (here, the second heating chamber 4A). Then, the workpiece W is loaded into the second heating chamber 4A and set on the rack member 25.

[0032] After the workpiece W is accommodated in the second heating chamber 4A, in the second heating chamber 4A, as shown in the intermediate cooling step K2 in FIG. 7, the workpiece W is cooled to the target temperature (here, 600 °C). At that time, the shutter mechanism 40 is operated to open, and as shown in FIG. 5, the openings 31, 32 of the heat insulating wall 21 are opened, and the workpiece W is radiatively cooled by the water-cooled panel 30. The temperature of the workpiece W is measured by the radiation thermometer 50, and when the workpiece W is cooled to a predetermined temperature near the target temperature (600 °C), this time the shutter mechanism 40 is operated to close, and the openings 31, 32 of the heat insulating wall 21 are closed by the heat insulating plate 41. Thereby, the cooling gradient near the target temperature is relaxed, and the undershoot with respect to the target soaking temperature is suppressed. Thereafter, the workpiece W is subjected to soaking heat treatment while being held at 600°C, which is the soaking holding temperature in isothermal annealing, under a vacuum atmosphere by heating with the second heater 27 (soaking step K3 in Fig. 7).

[0033] After the soaking heat treatment in the second heating chamber 4A is completed, the workpiece transfer mechanism 5 receives the workpiece W in the second heating chamber 4A, transfers the workpiece W to the position of the cooling chamber 6, and sets the workpiece W on the rack member 65 in the cooling chamber 6. In the cooling chamber 6, after the pressure is restored with the atmosphere gas (N2 gas) with the doors 63 and 64 closed, the atmosphere gas as the cooling gas is circulated while being cooled by the gas cooler 71 to cool the workpiece W to a temperature at which it can be taken out. Then, when the door 63 is opened and the workpiece W after cooling is taken out, a series of operations related to the heat treatment are completed.

[0034] As described above, in the heat treatment facility 1 of the present embodiment, since a series of processes from primary heating, intermediate cooling, and soaking are performed in a vacuum state, there is no need to perform pressure change operations such as pressure restoration and subsequent pressure reduction in the process of transitioning to each step of primary heating, intermediate cooling, and soaking, and the time required for a series of heat treatments can be shortened. Further, in the heat treatment facility 1 of the present embodiment, a plurality of first heating chambers 3A, 3B, 3C and a plurality of second heating chambers 4A, 4B, 4C are arranged in parallel inside the vacuum chamber 2, and heat treatment with different heat patterns can be performed for each heating chamber in the vacuum chamber 2. For example, when heat-treating workpieces W1, W2, and W3 with different optimal heat patterns simultaneously, the workpiece W1 is processed in the first heating chamber 3A and the second heating chamber 4A, the workpiece W2 is processed in the first heating chamber 3B and the second heating chamber 4B, and the workpiece W3 is processed in the first heating chamber 3C and the second heating chamber 4C, so that the heat treatment for each of the workpieces W1, W2, and W3 can be completed in the theoretically fastest transformation time or a time close thereto.

[0035] In the heat treatment equipment 1 of this embodiment, in the second heating chamber 4, a water-cooled panel 30 is provided on the side opposite to the work piece W with respect to the second heater 27, and a shutter mechanism 40 is provided between the second heater 27 and the water-cooled panel 30. Therefore, by closing the shutter (heat shield plate 41) provided between the second heater 27 and the water-cooled panel 30 at the end stage of the intermediate cooling in isothermal annealing (the stage approaching the target soaking temperature), the cooling gradient near the target soaking temperature can be relaxed, and the undershoot with respect to the target soaking temperature can be reduced. Also, by closing the shutter, the water-cooled panel 30 arranged close to the second heater 27 can be protected from the radiant heat of the second heater 27.

[0036] In the heat treatment equipment 1 of this embodiment, in the second heating chamber 4, the second heater 27, the water-cooled panel 30, and the shutter mechanism 40 are provided above and below the work piece W in the vertical direction, respectively, and the work piece W accommodated in the second heating chamber 4 can be heat-treated uniformly from the upper and lower two directions.

[0037] In the heat treatment equipment 1 of this embodiment, a radiation thermometer 50 for measuring the temperature of the work piece W accommodated inside is provided in the second heating chamber 4, and temperature control can be performed based on the temperature of the work piece W measured by the radiation thermometer 50.

[0038] As described above, the embodiments of the present invention have been described in detail, but this is merely an example. For example, the number and the parallel arrangement direction of the first heating chamber and the second heating chamber arranged in parallel in the vacuum chamber are not limited to the above embodiment and can be changed as appropriate. Similarly, the number and the arrangement position of the cooling chamber and the temporary placement chamber can be changed as appropriate. Also, in the above embodiment, an example of performing isothermal annealing using the heat treatment equipment has been shown, but in the heat treatment equipment of the present invention, other heat treatments (for example, spheroidizing annealing, etc.) can also be performed. The present invention can be configured in various modified forms without departing from the gist thereof.

Explanation of reference numerals

[0039] 1 Heat treatment equipment 2 Vacuum chamber 3 (3A, 3B, 3C) First Heating Chamber 4 (4A, 4B, 4C) Second Heating Chamber 5 Workpiece Transfer Mechanism 6 Cooling Chamber 17 First Heater 27 Second Heater 30 Water Cooling Panel 40 Shutter Mechanism 50 Radiation Thermometer W Workpiece

Claims

1. A heat treatment facility for heat-treating a metal workpiece, comprising: a vacuum chamber; a plurality of first heating chambers and a plurality of second heating chambers arranged in parallel inside the vacuum chamber; a cooling chamber for accommodating the workpiece and cooling the workpiece with a cooling gas; a workpiece transfer mechanism provided inside the vacuum chamber for transferring the workpiece between the first heating chamber, the second heating chamber, and the cooling chamber; and the first heating chamber has a first heater as a heating means; the second heating chamber has a second heater as a heating means and a water-cooled panel as a cooling means, the heat treatment facility.

2. The heat treatment facility according to claim 1, wherein in the second heating chamber, the water-cooled panel is provided on the side opposite to the workpiece with respect to the second heater, and a shutter mechanism is provided between the second heater and the water-cooled panel.

3. The heat treatment facility according to claim 2, wherein in the second heating chamber, the second heater, the water-cooled panel, and the shutter mechanism are provided above and below the workpiece in the vertical direction, respectively, with the workpiece interposed therebetween.

4. The heat treatment facility according to any one of claims 1 to 3, wherein the second heating chamber is provided with a radiation thermometer for measuring the temperature of the workpiece accommodated therein.

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