JP2010111893A - Heat-treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-treating method in which electrical discharge can be effectively prevented in an electric motor used for driving a fan for blowing a coolant gas onto an object to be treated and sufficient cooling performance can be obtained when cooling the object after heating by the coolant gas without causing complication of equipment structure, cost increase or the like. <P>SOLUTION: The heat-treating method includes performing the gas cooling of a heated workpiece 1 in a cooling chamber 3 by a fan 16 driven by an electric motor 15. The method includes the steps of: introducing the coolant gas into the cooling chamber 3 under such low pressures as not to generate the electrical discharge from the motor 15 in the cooling chamber 3; starting the motor 15 to increase its revolution until reaching a prescribed revolution; and introducing the coolant gas into the cooling chamber 3 so as to obtain the pressure to be used for cooling the workpiece 1. In order for the success of the above method, the first and second openable valves 35 and 38 are provided from the upstream side to the downstream side of a gas introduction channel 30 in turn. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat treatment method in which an object to be processed after heating is cooled by a refrigerant gas in quenching or the like.

  Conventionally, vacuum quenching has been performed as heat treatment using a metal workpiece or the like as a workpiece (object to be processed). In vacuum quenching, a workpiece is heated in vacuum (vacuum heating) and then rapidly cooled. As a method for cooling the workpiece after heating, there are a method using water or oil and a method using a refrigerant gas such as nitrogen gas.

  According to gas cooling (cooling by refrigerant gas), adjustment of quenching distortion (thermal deformation caused by rapid cooling) of the workpiece can be adjusted because the cooling rate can be easily adjusted in comparison with the method using water or oil. Advantages such as being easy and needing no workpiece cleaning are obtained. That is, according to the method using water or oil, when changing the cooling rate, it is necessary to exchange water or oil as a refrigerant. In this regard, according to the gas cooling, the cooling rate can be adjusted by adjusting the pressure of the refrigerant gas, the speed at which the refrigerant gas is introduced, and the like. In addition, when oil is used as the refrigerant, it is necessary to clean the workpiece soiled with oil. However, in the case of gas cooling, such cleaning is not necessary.

  For gas cooling, a configuration including a fan for blowing refrigerant gas to the heated workpiece is used. As a configuration including a fan, a fan is provided inside a processing chamber (referred to as a chamber or the like) in which a workpiece after heating exists, and a refrigerant gas introduced into the processing chamber is stirred by the fan. There is a configuration in which a fan is provided in a space communicating with a chamber via a pipe or the like, and refrigerant gas is introduced into the processing chamber by rotation of the fan. In general, an electric motor is used to drive the fan for gas cooling (see, for example, Patent Document 1). Patent Document 1 discloses a configuration in which a fan directly connected to a drive shaft of an electric motor is provided in a processing chamber.

  Thus, when an electric motor is used to drive a fan, discharge generated inside the electric motor in a vacuum becomes a problem. That is, the processing chamber in which the workpiece is cooled after the heat treatment by vacuum heating is in a vacuum state as in the case of heating. For this reason, in the configuration in which the space where the electric motor exists communicates with the processing chamber for cooling, the electric motor is exposed to a vacuum state when the workpiece is cooled. Therefore, when the electric motor is started in a vacuum state before the refrigerant gas is introduced, a discharge may occur inside the electric motor.

  For this reason, conventionally, in the operation of an electric motor for gas cooling, the refrigerant gas pressure (pressure in the processing chamber that changes due to introduction of the refrigerant gas, etc.) reaches a predetermined pressure (for example, atmospheric pressure (1 atm)). After that, the electric motor is started. That is, in this case, the electric motor is started at a timing at which the refrigerant gas pressure becomes a predetermined pressure immediately after the start of introduction of the refrigerant gas into the processing chamber so that no electric discharge occurs in the electric motor.

  In such an electric motor starting method, the rise of the refrigerant gas pressure and the acceleration of the fan rotated by the electric motor are performed at the same time. Therefore, the refrigerant gas pressure rises during the acceleration of the fan (electric motor). For this reason, when the fan acceleration time (the time from when the motor starts until the fan reaches a predetermined rotational speed) greatly affects the cooling rate (cooling capacity) in gas cooling, and a sufficient cooling rate cannot be obtained There is.

Specifically, the fan acceleration time tends to become longer as the moment of inertia of the electric motor or fan (usually determined by GD ² ; the same applies hereinafter) increases. Here, when it is going to increase the cooling capacity by a refrigerant gas by increasing the air volume by a fan, generally enlargement of a fan is performed. As the fan size increases, the moment of inertia of the fan increases, and the torque of the motor needs to be increased. As the torque of the motor increases, the moment of inertia of the motor increases. As described above, in gas cooling, it is difficult to achieve both a higher cooling rate and a shorter fan acceleration time, and a sufficient cooling rate may not be obtained.

  In this regard, in order to shorten the fan acceleration time, a method using a plurality of relatively small motors and fans can be considered. According to this method, since the motor and the fan are small, the moment of inertia and torque as described above are reduced, the fan acceleration time is shortened, and the air volume necessary for gas cooling is reduced by the plurality of motors and fans. Secured. However, according to the method using a plurality of electric motors and fans, there are problems such as an increase in equipment costs, a complicated layout of piping and the like, and an increase in installation area.

  Therefore, in order to reduce the influence of the fan acceleration time on the cooling rate in gas cooling, the following method is considered. That is, the refrigerant gas pressure is maintained at a low pressure that does not cause electric discharge in the motor during the fan acceleration time, and is increased to a pressure required for gas cooling after the fan reaches the set rotational speed. .

  The content about the timing which raises the refrigerant gas pressure in the relationship with such fan acceleration time is shown by patent document 2. FIG. However, Patent Document 2 does not indicate the specific contents of the method for adjusting the refrigerant gas pressure in relation to the fan acceleration time as described above, or the specific means for realizing the method.

  As described above, in order to increase the refrigerant gas pressure in two stages, that is, a pressure that is low enough not to cause discharge in the electric motor and a pressure that is necessary for gas cooling, the following method is generally considered. It is done. That is, in the gas introduction passage for introducing the refrigerant gas into the processing chamber, the refrigerant gas is boosted by a hydraulic pump or the like and stored using a tank or the like at a predetermined timing using an on-off valve or the like (two steps). (Ii) A method of introducing into the processing chamber.

However, when a common piping configuration (pump, tank, on-off valve, etc.) is used to raise the refrigerant gas pressure in two stages, the refrigerant gas is usually at each stage where the set pressure difference for the refrigerant gas pressure becomes large. It is difficult to stabilize the pressure. In particular, the low pressure that does not cause electric discharge in the electric motor is very low compared to the pressure required for gas cooling.Therefore, the refrigerant gas pressure rises too much, causing pressure fluctuations and stabilizing the refrigerant gas pressure. It is difficult to plan.
JP-A-10-183236 JP 2002-294333 A (FIG. 1 (a))

  The present invention has been made in view of the above-described problems, and the problem to be solved is that in the gas cooling for cooling the object to be processed after being heated by the refrigerant gas, the equipment structure is complicated and the cost is reduced. Heat treatment method capable of effectively preventing electric discharge in an electric motor used to drive a fan for blowing refrigerant gas to an object to be processed without causing an increase in temperature and the like and obtaining sufficient cooling capacity Is to provide.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, according to the first aspect of the present invention, the object to be processed after heating is convected by a fan that uses an electric motor provided in a space communicating with the processing chamber as a driving source in the processing chamber for storing the processing object. The refrigerant gas is cooled in the processing chamber so that the pressure in the processing chamber becomes a first pressure that is set in advance as a low pressure that does not cause discharge in the electric motor. In the state in which the refrigerant gas is introduced into the first stage and the pressure in the processing chamber is the first pressure, the electric motor is started, and the rotational speed of the electric motor is set in advance in relation to the driving of the fan. In a state where the fan is started up to a predetermined rotational speed and the rotational speed of the electric motor is at the predetermined rotational speed, the refrigerant gas is introduced into the processing chamber. And a late refrigerant gas introduction process in which the force is introduced so as to be a second pressure preset as a pressure used for cooling the workpiece, and the refrigerant supplied from a predetermined supply source First on-off valve means for opening and closing the gas introduction passage, which is provided in order from the upstream side to the downstream side in the introduction direction of the refrigerant gas in the gas introduction passage, which is a passage for introducing gas into the processing chamber And the first on-off valve means for opening and closing the first on-off valve means and the second on-off valve means in a closed state, and the first on-off valve in the gas introduction passage. From the state where the amount of the refrigerant gas corresponding to the first pressure is stored in a portion between the first on-off valve means and the second on-off valve means, the second on-off valve means is opened. Cold A gas introduction process is performed, the first on-off valve means is closed, the second on-off valve means is open, and the upstream portion of the first on-off valve means in the gas introduction passage In addition, the second refrigerant gas introduction process is performed by opening the first on-off valve means from a state where the amount of the refrigerant gas corresponding to the second pressure is stored.

  According to a second aspect of the present invention, a branch gas introduction passage that branches from the gas introduction passage and communicates with the space in which the electric motor is provided is provided on the downstream side of the first on-off valve means.

  According to a third aspect of the present invention, the object to be processed after heating is convected in a processing chamber containing the object to be processed by a fan having a motor as a drive source provided in a space communicating with the processing chamber. The refrigerant gas is introduced into the processing chamber so that the pressure in the processing chamber becomes a first pressure that is preset as low as not to cause discharge in the electric motor. In the state in which the refrigerant gas is introduced and the pressure in the processing chamber is the first pressure, the electric motor is started, and the rotational speed of the electric motor is set in advance in relation to the driving of the fan. In a state where the fan is started up until the number of revolutions reaches the predetermined number of revolutions, and the number of revolutions of the electric motor is the predetermined number of revolutions, the refrigerant gas is introduced into the processing chamber, and the pressure in the processing chamber is A late-stage refrigerant gas introduction process that introduces a second pressure that is set in advance as a pressure used for cooling the processed object, and the refrigerant gas supplied from a predetermined supply source is processed As a gas introduction passage that is a passage for introduction into a room, a first gas introduction passage that is the gas introduction passage for performing the first-stage refrigerant gas introduction process and the gas for performing the second-stage refrigerant gas introduction process A second gas introduction passage which is an introduction passage, and is provided in each of the first gas introduction passage and the second gas introduction passage, and includes an opening / closing valve means for opening and closing the gas introduction passage. , Using the first gas introduction passage, the on-off valve means of the first gas introduction passage is in a closed state, and the cooler than the on-off valve means in the first gas introduction passage. By opening the on-off valve means of the first gas introduction passage from a state in which the refrigerant gas in an amount corresponding to the first pressure is stored in the upstream portion in the gas introduction direction. , Performing the previous-stage refrigerant gas introduction process, using the second gas introduction passage, the on-off valve means of the second gas introduction passage being closed, and the on-off valve in the second gas introduction passage By opening the on-off valve means of the second gas introduction passage from a state in which the refrigerant gas in an amount corresponding to the second pressure is stored in the portion upstream of the means, The latter-stage refrigerant gas introduction process is performed.

  According to a fourth aspect of the present invention, a branch gas introduction passage that branches from the first gas introduction passage and communicates with the space in which the electric motor is provided on the downstream side of the on-off valve means of the first gas introduction passage. It is provided.

  According to a fifth aspect of the present invention, the temperature of the object to be processed before the refrigerant gas introduction process is increased in advance by an amount corresponding to the temperature decrease amount of the object to be decreased during the fan starting process. .

In Claim 6, the said temperature fall amount is estimated based on following Formula.
ΔT _w = {Q · t (T _f −T _s ) α} / A + T _s
Here, [Delta] T _w: the temperature decrease amount, Q: the average amount of air in the fan starting process, t: the time of the fan starting process, T _s: the fan startup process at the start of the temperature of the refrigerant gas, T _f: The temperature of the refrigerant gas at the end of the fan starting process, α: the specific heat of the refrigerant gas, and A: the heat dissipation coefficient of the workpiece to be obtained in advance.

In claim 7, when the temperature of the object to be processed before performing the refrigerant gas introduction process is increased to a predetermined target temperature set in advance,
The time of the fan starting process corresponding to raising the temperature of the object to be processed before the refrigerant gas introduction process to the target temperature is estimated based on the following equation.
t = {A (ΔT _wa −T _s )} / {Q (T _f −T _s ) α}
Here, t: time of the fan starting process, A: heat dissipation coefficient of the object to be processed obtained in advance, ΔT _wa : measured value of temperature decrease amount of the object to be processed that decreases during the fan starting process, and the object to be processed Sum of temperature rise when raising the temperature of the workpiece to the target temperature, T _s : temperature of the refrigerant gas at the start of the fan starting process, Q: average air volume during the fan starting process, T _f : The temperature of the refrigerant gas at the end of the fan starting process, α: the specific heat of the refrigerant gas.

As effects of the present invention, the following effects can be obtained.
That is, according to the present invention, in the gas cooling for cooling the object to be processed after being heated by the refrigerant gas, the refrigerant gas is blown to the object to be processed without incurring the complexity of the equipment structure or increasing the cost. Discharge in the electric motor used for driving the fan can be effectively prevented, and sufficient cooling ability can be obtained.

  In the gas cooling for cooling the object to be processed after being heated by the refrigerant gas, the present invention performs the introduction of the refrigerant gas into the processing chamber in which the object to be processed is introduced in two stages, thereby driving the pressure in the processing chamber. Proposed with a specific method of raising the pressure in two stages, a pressure that is low enough to prevent discharge in the electric motor (close to vacuum) and a relatively high pressure to cool the workpiece To do. Embodiments of the present invention will be described below. In this embodiment, a case where vacuum quenching using a metal workpiece or the like as an object to be processed will be described as an example of the heat treatment according to the present invention.

  A configuration of a heat treatment apparatus in which a heat treatment method according to an embodiment of the present invention is performed will be described with reference to FIG. As shown in FIG. 1, the heat treatment apparatus according to the present embodiment includes a heating chamber 2 for vacuum heating a workpiece 1 as a workpiece, and a cooling chamber for cooling the vacuum heated workpiece 1 with a refrigerant gas. 3. That is, the heat treatment apparatus according to the present embodiment has a two-chamber structure including the heating chamber 2 and the cooling chamber 3. The heating chamber 2 and the cooling chamber 3 are provided adjacent to each other via the intermediate chamber 4.

  The heating chamber 2 is a so-called vacuum heat treatment furnace for heating the workpiece 1 in vacuum. That is, heating for quenching the workpiece 1 is performed in a state where the inside of the heating chamber 2 in which the workpiece 1 is placed is depressurized to a predetermined degree of vacuum. For the heating chamber 2, an evacuation system 5 is provided for reducing the pressure in the heating chamber 2 to a predetermined degree of vacuum. The evacuation system 5 is configured by providing a pipe configuration to which a vacuum pump or the like is connected in a state in which communication or non-communication with the heating chamber 2 is switched by a switching valve or the like. As a vacuum pump which comprises the vacuum exhaust system 5, a rotary pump, a mechanical booster pump, a diffusion pump etc. are provided according to the desired degree of vacuum, for example.

  The heating chamber 2 has a heat insulating door 7 made of a refractory or the like on the intermediate chamber 4 side. That is, when the heat insulating door 7 is opened, the inside of the heating chamber 2 is in communication with the inside of the intermediate chamber 4. The heat insulating door 7 does not seal the heating chamber 2, and the heating chamber 2 and the intermediate chamber 4 have substantially the same pressure. The heating chamber 2 is provided with a supporting means such as a tray for setting the work 1 in a predetermined packing form, a heating means for heating the work 1 to a predetermined quenching temperature, and the like. As the heating means, for example, a graphite heater provided so as to surround the workpiece 1 set in the heating chamber 2 is used. The heating chamber 2 is provided with a work door 6 for performing maintenance and the like in the heating chamber 2.

  The cooling chamber 3 is for performing gas cooling (cooling with a refrigerant gas) on the workpiece 1 heated in vacuum in the heating chamber 2. That is, cooling for quenching the workpiece 1 is performed by introducing the refrigerant gas into the cooling chamber 3 in which the workpiece 1 is placed. In the gas cooling, the workpiece 1 is set in a predetermined packing form with respect to the tray 8 provided in the gas cooling chamber 3.

In the present embodiment, nitrogen gas (N ₂ gas) is used as the refrigerant gas for gas cooling. However, the type of refrigerant gas is not particularly limited. As the refrigerant gas, in addition to nitrogen gas, for example, an inert gas such as argon gas (Ar gas), air, or the like is used.

  The cooling chamber 3 has a partition door 9 on the intermediate chamber 4 side. That is, when the partition door 9 is opened, the gas cooling chamber 3 is in communication with the intermediate chamber 4. The cooling chamber 3 is provided with an opening / closing door 10 for taking the workpiece 1 into and out of the cooling chamber 3.

  The workpiece 1 heated in the heating chamber 2 is carried into the cooling chamber 3 through the intermediate chamber 4 and is cooled by gas. Specifically, after the workpiece 1 is heated in a vacuum in the heating chamber 2, the heat insulating door 7 of the heating chamber 2 and the partition door 9 of the cooling chamber 3 are opened, so that the heating chamber 2 and the cooling chamber 3 are intermediate chambers. 4 to communicate with each other. In such a communication state, the workpiece 1 in the heating chamber 2 is transferred into the cooling chamber 3 by a transfer means (not shown).

  Here, since the heat insulation door 7 and the partition door 9 are opened and the heating chamber 2 and the cooling chamber 3 are in communication with each other, the heating chamber 2 and the cooling chamber 3 are connected by a pipe 12 having a pressure equalizing valve 11. The That is, when the heat insulating door 7 and the partition door 9 are opened, the pressure equalizing valve 11 is opened for a predetermined time, so that the heating chamber 2 (and the intermediate chamber 4) and the cooling chamber 3 are equalized.

  The cooling chamber 3 is configured to be depressurized to a predetermined degree of vacuum by a vacuum exhaust system (not shown) as in the heating chamber 2. The vacuum state in the cooling chamber 3 is ensured by sealing the cooling chamber 3 with the partition door 9 and the opening / closing door 10. In addition, although illustration is abbreviate | omitted, the heating chamber 2 and the cooling chamber 3 have a valve for making the pressure in the heating chamber 2 or the cooling chamber 3 equal to the atmospheric pressure when the work door 6 and the opening / closing door 10 are opened. Piping is connected.

  As described above, the heating chamber 2 that can communicate with the intermediate chamber 4 via the heat insulating door 7 and the cooling chamber 3 that can communicate with the intermediate chamber 4 via the partition door 9 also include the intermediate chamber 4. It is possible to cut off the temperature via the switch and to adjust the pressure independently of each other.

  Next, the structure for gas cooling of the workpiece | work 1 is demonstrated. As shown in FIG. 1, the refrigerant gas introduced into the cooling chamber 3 is convected by a fan 16 using an electric motor (motor) 15 as a drive source. The fan 16 is directly connected to the drive shaft of the electric motor 15. Therefore, in the present embodiment, the rotational speed of the electric motor 15 is the rotational speed of the fan 16. The fan 16 is a centrifugal fan whose centrifugal direction is the blowing direction.

  The electric motor 15 and the fan 16 are accommodated in a motor housing 17 that forms a space communicating with the internal space of the cooling chamber 3. The refrigerant gas blown by the rotation of the fan 16 is guided into the cooling chamber 3 by the infeed duct 18 and sent out from the cooling chamber by the sending duct 19. Therefore, each of the feeding duct 18 and the sending duct 19 has one end connected to the cooling chamber 3 and the other end connected to the motor housing 17.

  The feeding duct 18 is a refrigerant gas feed pipe from the motor housing 17 to the cooling chamber 3. The feeding duct 18 is disposed from the motor housing 17 in a direction included in the centrifugal direction of the fan 16 (upward in this embodiment). In the present embodiment, the feeding duct 18 arranged upward from the motor housing 17 is connected to the upper side with respect to the cooling chamber 3. The feeding duct 18 is provided with a gas cooler 20 for lowering the temperature of the refrigerant gas introduced into the cooling chamber 3.

  The delivery duct 19 is a refrigerant gas return pipe from the cooling chamber 3 to the motor housing 17. In the present embodiment, the delivery duct 19 is connected to the lower side, which is the opposite side of the cooling chamber 3 to which the delivery duct 18 is connected. The delivery duct 19 is connected to the motor housing 17 in a direction along the axial direction of the electric motor 15.

  As a flow of the refrigerant gas between the cooling chamber 3 and the motor housing 17 in such a configuration, the refrigerant gas sent upward from the motor housing 17 by the rotating fan 16 by the feeding duct 18 is the cooling chamber 3. Is sent downward from above (see arrow A1). The refrigerant gas sent into the cooling chamber 3 is blown to the workpiece 1 on the tray 8 and is sent downward from the cooling chamber 3 by the sending duct 19 and sent into the motor housing 17 (see arrow A2). .

  As described above, the work 1 in the cooling chamber 3 is circulated by the refrigerant gas convection between the cooling chamber 3 and the motor housing 17 via the feeding duct 18 and the sending duct 19 by the fan 16 rotated by the electric motor 15. Is cooled. The refrigerant gas introduced into the cooling chamber 3 while being convected in this way is introduced through a gas introduction passage 30 from a predetermined supply source 31 for the refrigerant gas constituted by, for example, a gas cylinder.

  That is, as shown in FIG. 1, as described above, the inlet pipe 30 a for feeding the refrigerant gas into the refrigerant gas passage (hereinafter referred to as “convection passage”) that convects as the fan 16 rotates as described above. Is arranged. The introduction pipe 30a is connected to the infeed duct 18 constituting the convection passage. Therefore, in the present embodiment, a passage for introducing the refrigerant gas supplied from a predetermined supply source into the cooling chamber 3 by the introduction pipe 30a from the supply source 31 and a part of the feeding duct 18 is provided. A gas introduction passage 30 is configured.

  In addition, the connection position with respect to the convection channel | path of the introductory piping 30a is not specifically limited. That is, the introduction pipe 30a from the supply source 31 may be connected to any position in the infeed duct 18 and the outfeed duct 19 that constitute the convection passage. In other words, the introduction pipe 30 a from the supply source 31 is connected to the inlet duct 18 or the outlet duct 19 so that the refrigerant gas that has passed through the introduction pipe 30 a is sent from an arbitrary position in the flow of the refrigerant gas due to the rotation of the fan 16. It only has to be connected to.

  As described above, in the heat treatment method according to the present embodiment (vacuum quenching method, the same applies hereinafter), the workpiece 1 after heating is the cooling chamber 3 serving as a processing chamber in which the workpiece 1 is accommodated. The refrigerant gas is cooled by being convected by a fan 16 that uses an electric motor 15 provided in a motor housing 17 that is a space communicating with the motor 15 as a drive source.

  In the heat treatment method of the present embodiment, the pressure in the cooling chamber 3 (hereinafter referred to as “refrigerant gas pressure”) that changes due to the introduction of the refrigerant gas or the like when the workpiece 1 is gas-cooled is started by the motor 15. During the time from when the fan 16 reaches a predetermined rotational speed, the pressure is maintained at a low pressure that does not cause the electric motor 15 to discharge. Then, after the fan reaches a predetermined rotational speed, the refrigerant gas pressure is increased to a pressure required for gas cooling. Therefore, in the heat treatment method of the present embodiment, when the workpiece 1 is gas-cooled, the first-stage refrigerant gas introduction process, the fan start-up process, and the second-stage refrigerant gas introduction process are performed.

  In the first-stage refrigerant gas introduction process, the refrigerant gas is introduced into the cooling chamber 3 so that the refrigerant gas pressure becomes a first pressure that is set in advance as low pressure that does not cause discharge in the electric motor 15.

  The first-stage refrigerant gas introduction process is a refrigerant gas introduction process performed before the electric motor 15 is started. In the first stage refrigerant gas introduction process, a small amount of refrigerant gas is introduced into the cooling chamber 3 in the vacuum state in which the workpiece 1 after vacuum heating in the heating chamber 2 is carried in, so that the refrigerant gas pressure is increased. The pressure is raised to one. Due to the refrigerant gas introduction process in the previous period, the pressure in the motor housing 17 communicating with the inside of the cooling chamber 3 through the infeed duct 18 and the outfeed duct 19 becomes the first pressure.

  The first pressure used in the refrigerant gas introduction process in the previous period is set based on a so-called Paschen curve representing the relationship between the refrigerant gas pressure and the voltage at which electric discharge occurs in the electric motor 15 (discharge start voltage), for example. The Paschen curve is a graph showing the relationship between the gas pressure and the discharge start voltage at a predetermined distance between electrodes in a certain gas, and the discharge start voltage that is the discharge limit is the type of gas, the gas pressure, and the distance between the electrodes. Derived from Paschen's law, which is determined by distance.

  Therefore, in this embodiment in which nitrogen gas is used as the refrigerant gas, the Paschen curve used for setting the first pressure uses the minimum value of the distance between the coil constituting the motor 15 and the main body ground as the distance between the electrodes. The relationship between the pressure of nitrogen gas (refrigerant gas pressure) and the discharge start voltage in the electric motor 15 is shown. For this reason, the first pressure is set in the range of, for example, 0.005 to 0.1 MPa in the present embodiment, although it depends on variations in manufacturing accuracy of the motor 15 (individual differences).

  The lower limit (0.005 MPa in the above example) of the first pressure range is a value based on the viewpoint of the minimum pressure that does not cause discharge in the electric motor 15. Accordingly, the lower limit value of the first pressure range is defined to be slightly higher than the value of the refrigerant gas pressure corresponding to the discharge start voltage according to the Paschen curve, for example.

  In addition, the upper limit value (0.1 MPa in the above example) of the first pressure range is that the temperature of the workpiece 1 gradually decreases due to the refrigerant gas introduced into the cooling chamber 3 in the previous refrigerant gas introduction process. By doing so, the value is based on the viewpoint of suppressing the rapid cooling action of the workpiece 1 from being obtained in the latter-stage refrigerant gas introduction process. That is, when the amount of the refrigerant gas introduced into the cooling chamber 3 in the first refrigerant gas introduction process increases, the refrigerant gas is convected by the rotation of the fan 16 that is driven in the fan starting process after the first refrigerant gas introduction process. Thus, the temperature drop of the work 1 before the late refrigerant gas introduction process is started increases. When the temperature drop of the workpiece 1 before the late refrigerant gas introduction process becomes large in this way, the rapid cooling action of the workpiece 1 in the late refrigerant gas introduction process becomes insufficient (a sufficient cooling rate cannot be obtained). Therefore, the upper limit value of the first pressure range suppresses the temperature drop of the work 1 before the late refrigerant gas introduction process to such an extent that the cooling rate of the work 1 by gas cooling can be secured and the quenching quality is not impaired. To be specified.

  A fan starting process is performed after the refrigerant gas introducing process in the previous period. In the fan starting process, the electric motor 15 is started in a state where the pressure in the cooling chamber 3 is the first pressure, and the rotational speed of the electric motor 15 is a predetermined rotation set in advance in relation to the driving of the fan 16. Raised until number.

  The fan starting process is a process in which the rotational speed of the electric motor 15 is increased to a predetermined rotational speed in a state where the refrigerant gas pressure that has been increased to the first pressure in the previous refrigerant gas introduction process is maintained at the first pressure. In the present embodiment, as described above, the rotational speed of the electric motor 15 and the rotational speed of the fan 16 (hereinafter referred to as “fan rotational speed”) have a one-to-one correspondence, so the rotational speed of the electric motor 15 is a predetermined rotational speed. In the state, the fan rotational speed is also the same as the predetermined rotational speed. Therefore, in the present embodiment, the predetermined rotation speed of the electric motor 15 corresponds to the fan rotation speed that can obtain an air volume necessary for gas cooling of the workpiece 1 in relation to driving (rotation) of the fan 16. Is preset. Hereinafter, the fan rotation speed in a state where the rotation speed of the electric motor 15 is a predetermined rotation speed is referred to as “set rotation speed”.

  Thus, in the fan starting process, the fan 16 (electric motor 15) is stopped from the state where the rotation of the fan 16 (electric motor 15) is stopped until the electric motor 15 is started and the fan rotational speed reaches the set rotational speed. The rotation of is accelerated. Therefore, the elapsed time by the fan starting process corresponds to the time from when the electric motor 15 is started until the fan rotational speed reaches the set rotational speed (hereinafter referred to as “fan acceleration time”).

  In the fan starting process, since the refrigerant gas is held at the first pressure, the electric motor 15 is not discharged. Similarly, since the refrigerant gas is held at the first pressure (under a low pressure), even when the fan 16 rotates, the refrigerant gas that convects is small, so that the temperature drop of the work 1 is suppressed. The

  After the fan start-up process, a late refrigerant gas introduction process is performed. In the latter-stage refrigerant gas introduction process, the refrigerant gas is set in advance in the cooling chamber 3 and the refrigerant gas pressure is set in advance as a pressure used for cooling the workpiece 1 in a state where the rotation speed of the electric motor 15 is a predetermined rotation speed. It is introduced so as to be a second pressure.

  The latter-stage refrigerant gas introduction process is a refrigerant gas introduction process performed in a state where the fan rotation speed is a set rotation speed (a state where the rotation speed of the motor 15 is a predetermined rotation speed) by the motor 15 started in the fan start-up process. is there. In the latter-stage refrigerant gas introduction process, a large amount of refrigerant gas is introduced into the cooling chamber 3 held at the first pressure in comparison with the amount of refrigerant gas introduced in the first-stage refrigerant gas introduction process. Thus, the refrigerant gas pressure is increased from the first pressure to the second pressure.

  The second pressure used in the late refrigerant gas introduction process is set as a pressure corresponding to the amount of refrigerant gas introduced so as to obtain a sufficient quenching action for the workpiece 1 as a quenching target. The second pressure is usually set in the range of about 100 to several hundred times the first pressure.

  As described above, each process performed in the gas cooling of the workpiece 1 will be specifically described with reference to the graph shown in FIG. In FIG. 2, the graphs shown in (a) and (b) share the horizontal axis indicating time (sec), and the graph shown in (a) shows the change over time in the refrigerant gas pressure (MPa). The graph shown in (b) represents the time change of the fan rotation speed (rpm). Here, an example will be described in which the first pressure is set as 0.01 MPa, the set rotation speed for the fan rotation speed is set as 3600 rpm, and the second pressure is set as 1 MPa.

  As shown in FIG. 2 (a), in the vacuum state (pressure p0 <0.01 MPa) of the cooling chamber 3 in which the workpiece 1 after vacuum heating in the heating chamber 2 is carried (pressure p0 <0.01 MPa), the refrigerant gas introduction process is started ( Time t0). That is, in the previous refrigerant gas introduction process, a slight amount of refrigerant gas is introduced into the cooling chamber 3 at the pressure p0 while the electric motor 15 (fan 16) is stopped, so that the refrigerant gas pressure is reduced. The pressure is increased from p0 to 0.01 MPa. When the refrigerant gas pressure reaches 0.01 MPa, the first-stage refrigerant gas introduction process ends (time t1).

  As shown in FIG. 2B, the fan starting process is started at time t1 corresponding to the end of the previous refrigerant gas introducing process. That is, in the fan starting process, the motor 15 in a stopped state is started in a state where the refrigerant gas pressure is 0.01 MPa, and the rotation of the motor 15 is accelerated, whereby the fan rotation speed is increased to 3600 rpm. When the fan rotation speed reaches 3600 rpm, the fan start-up process ends (time t2). Therefore, in this example, the fan acceleration time is the time from time t1 to time t2. As shown in FIG. 2A, the refrigerant gas pressure is maintained at 0.01 MPa during the fan acceleration time.

  The late refrigerant gas introduction process is started at time t2 corresponding to the end of the fan start-up process. That is, in the latter-stage refrigerant gas introduction process, a large amount of refrigerant is compared with the amount of refrigerant gas introduced in the first-stage refrigerant gas introduction process with respect to the 0.01 MPa cooling chamber 3 in a state where the fan rotational speed is 3600 rpm. By introducing the gas, the refrigerant gas pressure is increased from 0.01 MPa to 1 MPa. In this way, the refrigerant gas pressure increases, and the workpiece 1 is cooled by the convection of the refrigerant gas in the convection passage.

  In the heat treatment method of the present embodiment, the following configuration is used to perform each of these processes. That is, as shown in FIG. 1, the gas introduction passage 30 is provided in order from the upstream side (hereinafter simply referred to as “upstream side”) to the downstream side (also referred to as “downstream side”) in the refrigerant gas introduction direction. The first opening / closing valve 35 and the second opening / closing valve 38 are included.

  The first on-off valve 35 is provided on the downstream side of the reserve tank 34 in the gas introduction passage 30. The first opening / closing valve 35 functions as first opening / closing valve means for opening / closing the gas introduction passage 30. That is, in the open state of the first on-off valve 35, the flow of the refrigerant gas at the position of the first on-off valve 35 is ensured, and in the closed state of the first on-off valve 35, the refrigerant gas at the position of the first on-off valve 35 is secured. Is stopped.

  The second on-off valve 38 is provided downstream of the first on-off valve 35 in the gas introduction passage 30. The second on-off valve 38 functions as second on-off valve means for opening and closing the gas introduction passage 30, similarly to the first on-off valve 35. The first on-off valve 35 and the second on-off valve 38 are not particularly limited as long as they have a function capable of opening and closing the gas introduction passage 30.

  Further, a booster unit 33 is provided in the gas introduction passage 30. The pressure increasing unit 33 functions as pressure increasing means for increasing the pressure of the refrigerant gas from the supply source 31. The step-up unit 33 includes a hydraulic pump 33a that uses the electric motor 33b as a drive source. However, for example, in the case where the pressure of the refrigerant gas supplied from the supply source 31 is sufficient as the pressure used for gas cooling of the workpiece 1, the boosting unit 33 can be omitted.

  Further, a reserve tank 34 is provided in the gas introduction passage 30. The reserve tank 34 is provided downstream of the pressure increasing unit 33 in the gas introduction passage 30 and upstream of the first opening / closing valve 35. The reserve tank 34 functions as a storage unit that stores the refrigerant gas whose pressure has been increased by the pressure increasing unit 33. As the reserve tank 34, the volume of the cooling chamber 3 and the gas introduction passage 30 are set so that the refrigerant gas stored by using the reserve tank 34 is introduced into the cooling chamber 3 to obtain a desired refrigerant gas pressure. Based on the length, tube diameter, etc., those having the required volume are used.

  In the gas introduction passage 30, a pressure adjustment valve 36 is provided in parallel with the first opening / closing valve 35. The pressure regulating valve 36 is provided in a branch pipe 37 having a small pipe diameter with respect to the gas introduction passage 30. One end side of the branch pipe 37 is connected to the upstream side of the first on-off valve 35 in the introduction pipe 30 a, and the other end side is similarly connected to the downstream side of the first on-off valve 35. The pressure adjustment valve 36 finely adjusts the flow rate of the refrigerant gas when the first opening / closing valve 35 in the gas introduction passage 30 is open.

  The refrigerant gas piping configuration of the present embodiment is preferably provided with the following configuration. That is, as shown in FIG. 1, in this embodiment, the branch gas that branches from the gas introduction passage 30 and communicates with the motor housing 17, which is a space in which the electric motor 15 is provided, downstream of the first opening / closing valve 35. An introduction passage 40 is provided.

  In the present embodiment, the branch gas introduction passage 40 is branched from a position between the first on-off valve 35 and the second on-off valve 38 on the downstream side of the first on-off valve 35 in the gas introduction passage 30, and the motor housing 17. Connected to. The branch gas introduction passage 40 has a smaller pipe diameter than the gas introduction passage 30. The branch gas introduction passage 40 is a passage for the refrigerant gas for directly feeding a part of the refrigerant gas guided into the cooling chamber 3 by the gas introduction passage 30 into the motor housing 17.

  That is, with respect to the refrigerant gas introduced into the motor housing 17, the refrigerant gas introduced into the cooling chamber 3 by the gas introduction passage 30 is added to the refrigerant gas convection through the convection passage by the rotation of the fan 16, and the branch gas introduction passage 40. Thus, the refrigerant gas in the gas introduction passage 30 is branched and introduced. The branch gas introduction passage 40 is provided with a branch on / off valve 41 that opens and closes the branch gas introduction passage 40.

  The heat treatment method of the present embodiment performed by the heat treatment apparatus having the above configuration will be described with reference to the flowchart shown in FIG. In the heat treatment method of the present embodiment, after the workpiece 1 is vacuum heated (S10) in the heating chamber 2, the workpiece 1 is cooled in the cooling chamber 3 (S20). In the gas cooling of the work 1, the above-described processes, that is, the first-stage refrigerant gas introduction process (S21), the fan start-up process (S22), and the second-stage refrigerant gas introduction process (S23) are performed.

  In the apparatus configuration of this embodiment, the refrigerant gas introduction process (S21) is performed as follows. That is, in the first-stage refrigerant gas introduction process, first, the first on-off valve 35 is in the open state and the second on-off valve 38 is in the closed state, upstream of the second on-off valve 38 in the gas introduction passage 30. The pressure due to the refrigerant gas is set to a predetermined pressure for the refrigerant gas introduction process (hereinafter referred to as “pressure for the previous period”). In other words, the pressure of the refrigerant gas from the supply source 31 is increased by the booster unit 33 with the first on-off valve 35 in the open state and the second on-off valve 38 in the closed state. The upstream side (portion including the boosting unit 33 and the reserve tank 34) is used as the first-stage pressure.

  Then, the first on-off valve 35 is closed while the upstream side of the second on-off valve 38 is set to the pressure for the previous period. As a result, the pipe portion 30t (see FIG. 1) constituting the portion between the first on-off valve 35 and the second on-off valve 38 in the gas introduction passage 30 (hereinafter referred to as “valve passage portion”) is used for the previous period. The pressure refrigerant gas is stored. That is, when the first on-off valve 35 and the second on-off valve 38 are closed, the refrigerant gas having the pressure for the previous period is stored in a closed space (inside the pipe) formed by the pipe portion 30t. During the refrigerant gas introduction process in the previous period, the pressure regulating valve 36 provided in the branch pipe 37 communicating with the pipe portion 30t is closed.

  The second on-off valve 38 is opened from the state in which the refrigerant gas having the previous pressure is stored in the inter-valve passage portion including the pipe portion 30t. Accordingly, the refrigerant gas in the inter-valve passage portion is introduced into the cooling chamber 3 through the gas introduction passage 30 by a differential pressure with respect to the vacuum state (pressure p0).

  Thus, in this embodiment, while the 1st on-off valve 35 and the 2nd on-off valve 38 are a closed state, the pressure | voltage riser unit 33 is used for the passage part between valves, and 1st pressure (0.01 MPa) The refrigerant gas introduction process is performed by opening the second on-off valve 38 from the state where the amount of refrigerant gas corresponding to is stored.

  Therefore, during the first-stage refrigerant gas introduction process, the first-stage pressure (the amount of refrigerant gas stored) due to the refrigerant gas being stored in the pressure in the inter-valve passage portion is the volume of the cooling chamber 3 and the length of the gas introduction passage 30. Based on the pipe diameter, etc., the refrigerant gas in the inter-valve passage portion is introduced into the cooling chamber 3 so that the refrigerant gas pressure reaches the first pressure (the amount of refrigerant gas). Is done. Thus, in the inter-valve passage portion, the state in which the refrigerant gas having the first pressure is stored corresponds to the state in which the amount of the refrigerant gas corresponding to the first pressure is stored.

  Further, in the piping configuration in which the branch gas introduction passage 40 is provided as described above, in the inter-valve passage portion where the amount of refrigerant gas corresponding to the first pressure is stored during the refrigerant gas introduction process in the previous period, A part of the branch gas introduction passage 40 is included.

  Specifically, a pipe portion 40t (see FIG. 1) upstream of the branch opening / closing valve 41 in the branch gas introduction passage 40 is included in the inter-valve passage portion. That is, in the piping configuration in which the branch gas introduction passage 40 is provided, the piping portion 30t of the gas introduction passage 30 and the piping portion 40t of the branch gas introduction passage 40 that are communicated with each other are included in the inter-valve passage portion.

  Therefore, during the first-stage refrigerant gas introduction process, when the pressure increase unit 33 sets the inter-valve passage portion to the first-stage pressure, the second on-off valve 38 and the branch on-off valve 41 (and the pressure regulating valve 36) are closed. The first on-off valve 35 is closed in a state where the upstream side of the second on-off valve 38 and the branch on-off valve 41 is set to the pre-stage pressure, so that the refrigerant of the pre-pressure is supplied to the inter-valve passage portion. The gas is stored. That is, when the first on-off valve 35, the second on-off valve 38, and the branch on-off valve 41 (and the pressure adjustment valve 36) are closed, a closed space (mainly formed by the pipe portion 30t and the pipe portion 40t ( The refrigerant gas at the pressure for the previous period is stored in the inside of the pipe).

  Then, from the state in which the refrigerant gas of the previous pressure is stored in the inter-valve passage portion, that is, from the state in which the amount of the refrigerant gas corresponding to the first pressure is stored, the second on-off valve 38 and the branch on-off valve 41 It is opened at the same timing. Accordingly, the refrigerant gas in the inter-valve passage portion is introduced into the cooling chamber 3 and the motor housing 17 by the differential pressure with respect to the vacuum state (pressure p0). That is, the refrigerant gas in the inter-valve passage portion is introduced into the cooling chamber 3 by the gas introduction passage 30 when the second opening / closing valve 38 is opened, and the branch gas introduction passage is opened by opening the branch opening / closing valve 41. 40 is introduced into the motor housing 17. In the case where the branch gas introduction passage 40 is provided, the refrigerant gas introduction process is performed in this manner.

  As described above, the branch gas introduction passage 40 is used in the refrigerant gas introduction process in the previous period, so that the pressure in the motor housing 17 can be efficiently increased to the first pressure. That is, the pressure in the motor housing 17 in which the electric motor 15 exists is provided by providing the branch gas introduction passage 40 as compared with the case where the introduction of the refrigerant gas in the previous refrigerant gas introduction process is performed only by the gas introduction passage 30. Can be raised to the first pressure in a short time. As a result, it is possible to shorten the time of the refrigerant gas introduction process in the previous period, and to suppress the temperature drop of the work 1 over time in the process of introducing the refrigerant gas in the previous period.

  The branch position of the branch gas introduction passage 40 with respect to the gas introduction passage 30 is not particularly limited as long as it is downstream of the first opening / closing valve 35 in the gas introduction passage 30. For example, the branch gas introduction passage 40 may be branched from a portion of the gas introduction passage 30 on the downstream side of the second opening / closing valve 38. In this case, the branch opening / closing valve 41 can be omitted.

  In the apparatus configuration of the present embodiment, the late refrigerant gas introduction process (S23) is performed as follows. That is, in the late refrigerant gas introduction process, the pressure by the refrigerant gas upstream of the first open / close valve 35 in the gas introduction passage 30 in the gas introduction passage 30 is in the late refrigerant gas introduction process when the first open / close valve 35 is closed. The predetermined pressure (hereinafter referred to as “late pressure”). That is, with the first opening / closing valve 35 closed, the pressure of the refrigerant gas from the supply source 31 is increased by the boosting unit 33, and the upstream side of the first opening / closing valve 35 (the boosting unit 33 and the reserve tank). 34) is the late pressure. Here, the refrigerant gas having the upstream pressure upstream from the first on-off valve 35 is mainly stored in the reserve tank 34 on the upstream side of the first on-off valve 35.

  The state where the upstream side of the first opening / closing valve 35 is set to the late pressure is ensured by the opening / closing valve 32 (see FIG. 1). The on-off valve 32 opens and closes the gas introduction passage 30, and is provided downstream of the supply source 31 in the gas introduction passage 30 and upstream of the boosting unit 33. That is, when the first on-off valve 35 is closed and the pressure of the refrigerant gas raised by the pressure increasing unit 33 reaches the late pressure, the on-off valve 32 is closed, whereby the gas introduction passage 30 is closed. The pressure in the portion between the on-off valve 32 and the first on-off valve 35 is maintained at the late pressure. Note that the on-off valve 32 for holding the upstream side of the first on-off valve 35 at the later pressure may be provided between the pressure increasing unit 33 and the reserve tank 34 in the gas introduction passage.

  In addition, as the closing operation of the first opening / closing valve 35 when the upstream side of the first opening / closing valve 35 is set to the latter-stage pressure (operation for entering the closed state), for example, as described above, the first-stage refrigerant gas introduction process At this time, a closing operation for storing the refrigerant gas having the pressure for the previous period in the passageway between valves is used. In this case, the first on-off valve 35 is closed in order to confine the refrigerant gas having the first-stage pressure in the inter-valve passage portion, and then the pressure upstream of the first on-off valve 35 is increased to the second-stage pressure by the boosting unit 33. The

  Then, the upstream side of the first on-off valve 35 (between the on-off valve 32 and the first on-off valve 35) is set to the late pressure, that is, the upstream portion of the first on-off valve 35 in the closed state (main The first on-off valve 35 is opened from the state in which the refrigerant gas having the later pressure is stored in the reserve tank 34). Accordingly, the refrigerant gas between the on-off valve 32 and the first on-off valve 35 is caused to flow through the gas introduction passage 30 due to a differential pressure with respect to the first pressure (the late pressure is sufficiently higher than the first pressure). It is introduced into the cooling chamber 3.

  That is, the refrigerant gas having the latter pressure is stored in the state where the refrigerant gas pressure is the first pressure by the refrigerant gas introduced by opening the second on-off valve 38 in the first refrigerant gas introduction process. Therefore, when the first on-off valve 35 that is closed is opened, the refrigerant gas upstream of the first on-off valve 35 causes the second on-off valve 38 that is opened by the gas introduction passage 30 to pass through. Through the cooling chamber 3.

  As described above, in the present embodiment, the first on-off valve 35 is closed and the second on-off valve 38 is in the open state, and the second upstream of the first on-off valve 35 in the gas introduction passage 30 When the first on-off valve 35 is opened from the state in which the amount of refrigerant gas corresponding to the pressure (1 MPa) is stored, the latter-stage refrigerant gas introduction process is performed.

  Therefore, during the latter-stage refrigerant gas introduction process, the latter-stage pressure (the amount of refrigerant gas stored) due to the refrigerant gas being stored with respect to the pressure upstream of the first opening / closing valve 35 is the volume of the cooling chamber 3 and the gas introduction. A pressure at which the refrigerant gas pressure reaches the second pressure by introducing the refrigerant gas upstream of the first opening / closing valve 35 into the cooling chamber 3 based on the length, pipe diameter, etc. of the passage 30. It is set as (amount of refrigerant gas).

  Further, when the late pressure is set, the volume of the reserve tank 34 that constitutes a main part in which the refrigerant gas is stored upstream of the first opening / closing valve 35 is taken into consideration. That is, the volume of the reserve tank 34 is set as a volume capable of storing an amount of refrigerant gas upstream of the first opening / closing valve 35 such that the refrigerant gas pressure reaches the second pressure by the late refrigerant gas introduction process. The As described above, the state in which the refrigerant gas of the late pressure is stored in the upstream portion of the first opening / closing valve 35 in the gas introduction passage 30 is the state in which the amount of the refrigerant gas corresponding to the second pressure is stored. It corresponds to.

  In the latter-stage refrigerant gas introduction process, the opening / closing state of the branch opening / closing valve 41 is not particularly limited. This is because the second pressure is sufficiently higher than the first pressure (for example, 1 MPa with respect to 0.01 MPa) and the pipe diameter of the branch gas introduction passage 40 is small with respect to the gas introduction passage 30. based on. That is, in the latter-stage refrigerant gas introduction process, the refrigerant gas is introduced into the cooling chamber 3 by the gas introduction passage 30 and the refrigerant gas pressure rises to the second pressure. The impact of being introduced is small. For this reason, in the latter-stage refrigerant gas introduction process, whether or not the branch gas introduction passage 40 is used, that is, the open / close state of the branch on-off valve 41 is not particularly limited.

  After the late refrigerant gas introduction process, the refrigerant gas pressure is maintained at the second pressure. When the pressure is maintained during the late refrigerant gas introduction process or after the late refrigerant gas introduction process, the flow rate of the refrigerant gas introduced into the cooling chamber 3 is finely adjusted by the pressure adjustment valve 36.

  As described above, an example of gas cooling (S20) of the workpiece 1 in which the apparatus configuration of the present embodiment is used and the first refrigerant gas introduction process (S21) and the second refrigerant gas introduction process (S23) are performed will be described.

  In the gas cooling (S20), first, the first on-off valve 35 is opened and the second on-off valve 38 and the branch on-off valve 41 are closed. After the upstream side of the valve 41 is set to the initial pressure, the first on-off valve 35 is closed. From this state, the second opening / closing valve 38 and the branch opening / closing valve 41 are opened at the same timing, whereby the refrigerant gas introduction process (S21) is performed. That is, the refrigerant gas pressure is raised to the first pressure.

  After the refrigerant gas introduction process (S21) is performed, the fan start process (S22) is performed. That is, with the refrigerant gas pressure being the first pressure, the electric motor 15 is started and accelerated until the fan speed reaches the set speed.

  After the first on-off valve 35 is closed in the first-stage refrigerant gas introduction process (S21), in parallel with the first-stage refrigerant gas introduction process (S21) and the fan start-up process (S22), upstream of the first on-off valve 35. In the portion on the side, the reserve tank 34 is used to store the refrigerant gas in the late refrigerant gas introduction process (S23). That is, the portion upstream of the first opening / closing valve 35 is used as the late pressure.

  Then, the first on-off valve 35 is opened from the state where the fan rotational speed has reached the set rotational speed in the fan starting process (S22), whereby the late refrigerant gas introducing process (S23) is performed. That is, the refrigerant gas pressure is increased to the second pressure. Thereafter, the workpiece 1 is cooled by the convection refrigerant gas while the refrigerant gas pressure is maintained at the second pressure.

  According to the heat treatment method of the present embodiment as described above, in the gas cooling in which the workpiece 1 after being heated by the refrigerant gas is cooled, the refrigerant gas is supplied to the workpiece 1 without incurring a complicated equipment structure or an increase in cost. Discharge in the electric motor 15 used for driving the fan 16 for blowing air can be effectively prevented, and sufficient cooling ability can be obtained.

  That is, in the heat treatment method of the present embodiment, the refrigerant gas pressure is low enough to prevent discharge in the electric motor 15 during the fan start-up process (during the fan acceleration time) by performing the refrigerant gas introduction process in the previous period. This is a pressure (first pressure) state, and the amount of refrigerant gas introduced into the cooling chamber 3 is also small. For this reason, during the fan acceleration time, the electric motor 15 is prevented from being discharged, and the state of low cooling ability is maintained even when the fan rotation speed increases to the set rotation speed. Then, in a state where the fan rotation speed reaches the set rotation speed, the refrigerant gas pressure is increased to a pressure (second pressure) required for gas cooling by the late-stage refrigerant gas introduction process. Thereby, the influence of the fan acceleration time on the cooling rate in gas cooling is reduced, and a sufficient cooling rate (cooling capacity) for quenching the workpiece 1 is obtained.

  In the heat treatment method of the present embodiment, the set pressure for the refrigerant gas pressure is usually different by about two orders of magnitude (for example, 0.01 MPa and 1 MPa). The configuration (the gas introduction passage 30) is performed. For this reason, it becomes easy to avoid the complexity of an equipment structure, the increase in cost, etc.

  Specifically, in the pipe configuration of the present embodiment, a part of the gas introduction passage 30 for introducing the refrigerant gas into the cooling chamber 3 (see the pipe portion 30t) is used for pressure control for the refrigerant gas introduction process in the previous period. It is used as a reserve tank. For this reason, it is possible to reduce equipment costs, equipment maintenance costs, equipment operating costs, etc., and to simplify and compact equipment.

  Further, according to the heat treatment method of the present embodiment, when preventing discharge in the electric motor 15, the space (in the motor housing 17) in which the electric motor 15 is provided is kept airtight with respect to the cooling chamber 3 or a space communicating with the cooling chamber 3. Therefore, a sealing structure for the purpose is unnecessary. From this point as well, complication of the apparatus configuration can be prevented.

  The effect of the heat treatment method of the present embodiment will be described by comparison with a heat treatment method (hereinafter referred to as “conventional method”) in which refrigerant gas is introduced in one stage. First, the conventional method will be described with reference to the graph shown in FIG. In FIG. 4, similarly to FIG. 2, the graph shown in (a) represents the change over time in the refrigerant gas pressure, and the graph shown in (b) represents the change over time in the fan rotation speed. In addition, about the structure etc. which are common in this embodiment in a conventional method, it quotes using the same code | symbol etc. for convenience.

  In the conventional method, as shown in FIGS. 4A and 4B, in the vacuum state (pressure p0 <0.01 MPa) of the cooling chamber 3 in which the work 1 after vacuum heating in the heating chamber 2 is carried, the cooling chamber 3 starts to be introduced into the refrigerant gas (time t3). Then, the motor 15 is started at a timing (time t4) at which the refrigerant gas pressure reaches a predetermined pressure (0.01 MPa in this example) at which no discharge occurs in the motor 15. After the motor 15 is started, the fan speed is increased to the set speed (3600 rpm in this example).

  In the conventional method, the refrigerant gas pressure reaches a predetermined pressure (1 MPa in this example) used for cooling the workpiece 1 after its rise is started (after introduction of the refrigerant gas into the cooling chamber 3 is started). Until it is raised gradually (uniformly). Therefore, in the conventional method, the rise of the refrigerant gas pressure and the acceleration of the fan 16 rotated by the electric motor 15 are performed at the same time. Therefore, the refrigerant gas pressure increases during the acceleration of the fan 16 (electric motor 15). For this reason, the fan acceleration time greatly affects the cooling rate in gas cooling (cooling capacity, the same applies hereinafter), and a sufficient cooling rate may not be obtained.

  FIG. 5 shows the fan acceleration time (sec) and the hardness of a quenched product (Vickers hardness: Hv) obtained by vacuum-quenching the workpiece 1 for each of the conventional method and the heat treatment method of the present embodiment. An example of the experimental result about the relationship is shown. In FIG. 5, the present example (measurement points indicated by white circles) shows the experimental results by the heat treatment method of the present embodiment, and the conventional example (measurement points indicated by black squares) shows the experimental results by the conventional method. In this experimental result example, the hardness of the quenched product is measured every 1 second from the fan acceleration time of 1 second to 6 seconds.

  As shown in FIG. 5, according to the conventional method, the hardness of the hardened product decreases as the fan acceleration time becomes longer. Specifically, for the conventional example, when the fan acceleration time is 1 sec, the hardness of the quenched product is about Hv650, but as the fan acceleration time increases, the hardness of the quenched product decreases. Decrease gradually. In this example, when the fan acceleration time is 6 sec, the hardness of the quenched product is reduced to about Hv280. As described above, the hardness of the quenched product decreases as the fan acceleration time increases. In the conventional method, as described above, the fan acceleration time greatly affects the cooling rate in gas cooling, and a sufficient cooling rate is obtained. Because it is not possible.

  On the other hand, according to the heat treatment method of the present embodiment, the hardness of Hv600 or higher is maintained for the quenched product during the fan acceleration time of 1 to 6 seconds. That is, according to the heat treatment method of the present embodiment, the influence of the fan acceleration time on the cooling rate in the gas cooling is reduced, so that the hardness of the quenched product is reduced even if the fan acceleration time is increased to some extent. Is suppressed. This makes it possible to easily obtain good quenching quality in relation to the fan acceleration time.

  In the above-described embodiment of the present invention (hereinafter referred to as “first embodiment”), in the gas cooling of the workpiece 1, the first refrigerant gas introduction process and the latter refrigerant gas introduction process have the same system piping configuration (gas introduction). Although these processes are performed by the passage 30), these processes can also be performed by a separate piping configuration provided for performing each process. An example of the piping configuration in this case will be described with reference to FIG. 6 as another embodiment of the present invention. In the description of the present embodiment, the same reference numerals are used for portions common to the configuration in the first embodiment, and the description thereof is omitted as appropriate, and based on the configuration in the first embodiment (quoting the configuration Explain).

  In the present embodiment, the first gas introduction passage for performing the refrigerant gas introduction process is used as the gas introduction passage which is a passage for introducing the refrigerant gas supplied from the predetermined supply source 31 into the cooling chamber 3. A first-stage passage 50 as a gas introduction passage and a second-stage passage 60 as a second gas introduction passage which is a gas introduction passage for performing a second-stage refrigerant gas introduction process are provided. A storage means for storing refrigerant gas such as a reserve tank is provided in each passage.

  Specifically, in this embodiment, as shown in FIG. 6, the gas introduction passage 30 in the piping configuration of the first embodiment is used as the late passage 60. In this case, the second on-off valve 38 (see FIG. 1) is omitted from the gas introduction passage 30, and a piping configuration including the boosting unit 33, the reserve tank 34, and the first on-off valve 35 is used as the late passage 60. It is done. Therefore, in the present embodiment, the first opening / closing valve 35 functions as an opening / closing valve means for opening / closing the late passage 60.

  An early passage 50 is provided for such a late passage 60. The first-stage passage 50 is configured by branching from the upstream side of the reserve tank 34 on the downstream side of the boosting unit 33 in the introduction pipe 30a. That is, in this embodiment, the latter passage 60 and the first passage 50 share the boosting unit 33 as a boosting means for increasing the pressure of the refrigerant gas. However, boosting means such as the boosting unit 33 may be provided in each of the latter passage 60 and the first passage 50. Further, the boosting unit 33 can be omitted as described above.

  Since the first-stage passage 50 is for increasing the refrigerant gas pressure to the first pressure, the first-stage passage 50 is configured by a small-diameter pipe with respect to the second-stage passage 60. An opening / closing valve 55 is provided in the first-stage passage 50 on the downstream side of the booster unit 33. The on-off valve 55 functions as an on-off valve means for opening and closing the first passage 50.

  Further, a reserve tank 54 is provided in the first-stage passage 50. The reserve tank 54 is provided on the downstream side of the booster unit 33 in the first-stage passage 50 and on the upstream side of the on-off valve 55. The reserve tank 54 functions as a storage unit that stores the refrigerant gas whose pressure has been increased by the pressure increasing unit 33. As the reserve tank 54, the volume of the cooling chamber 3 and the passage 50 of the previous period 50 are used so that the refrigerant gas stored by using the reserve tank 54 is introduced into the cooling chamber 3 to obtain a desired refrigerant gas pressure. Based on the length, tube diameter, etc., those having the required volume are used. Therefore, the reserve tank 54 has a smaller volume than the reserve tank 34 provided in the later-stage passage 60 used in the later-stage refrigerant gas introduction process in which the set pressure for the refrigerant gas pressure is higher than that in the earlier-stage refrigerant gas introduction process. .

  The first-stage passage 50 is mainly configured by an introduction pipe 50 a branched from the introduction pipe 30 a constituting the latter-stage passage 60. The introduction pipe 50a is connected to the infeed duct 18 constituting the convection passage. Therefore, in the present embodiment, the first-stage passage 50 is configured by the introduction pipe 50 a branched from the introduction pipe 30 a and a part of the feeding duct 18. In addition, the connection position with respect to the convection channel | path of the introductory piping 50a is not specifically limited. That is, the introduction pipe 50a may be connected to any position in the infeed duct 18 and the outfeed duct 19 that constitute the convection passage.

  The refrigerant gas piping configuration of the present embodiment is preferably provided with the following configuration. That is, as shown in FIG. 6, in the present embodiment, in the motor housing 17, which is a space where the electric motor 15 is provided by branching from the previous passage 50, downstream of the opening / closing valve 55 of the previous passage 50. A branch gas introduction passage 70 is provided.

  The branch gas introduction passage 70 has substantially the same pipe diameter as that of the introduction pipe 50 a constituting the first-stage passage 50. The branch gas introduction passage 70 is a passage for the refrigerant gas for directly feeding a part of the refrigerant gas introduced into the cooling chamber 3 by the first passage 50 into the motor housing 17.

  That is, with respect to the refrigerant gas introduced into the motor housing 17, the refrigerant gas introduced into the cooling chamber 3 by the previous passage 50 is added to the refrigerant gas convection through the convection passage by the rotation of the fan 16, and the branch gas introduction passage 70. As a result, the refrigerant gas in the first passage 50 is branched and introduced.

  In the apparatus configuration of this embodiment, the refrigerant gas introduction process (S21) is performed as follows. That is, the first-stage refrigerant passage 50 is used in the first-stage refrigerant gas introduction process. That is, in the previous-stage refrigerant gas introduction process, the refrigerant gas supplied from the supply source 31 and boosted by the booster unit 33 is introduced into the first-pass passage 50 side. Therefore, in the first-stage refrigerant gas introduction process, introduction of the refrigerant gas to the second-stage passage 60 is restricted by an open / close valve (not shown).

  In the first stage refrigerant gas introduction process, the pressure by the refrigerant gas upstream of the on / off valve 55 in the first period passage 50 is set as the first period pressure with the on / off valve 55 closed. In other words, the pressure of the refrigerant gas from the supply source 31 is increased by the booster unit 33 with the open / close valve 55 closed, and the upstream side of the open / close valve 55 (including the booster unit 33 and the reserve tank 54). ) Is the pressure for the previous period. Here, the refrigerant gas having the upstream pressure upstream of the on-off valve 55 is stored mainly in the reserve tank 54 on the upstream side of the on-off valve 55. Further, the on / off valve 32 ensures that the upstream side of the on / off valve 55 is at the initial pressure.

  As a result, the upstream side of the on-off valve 55 (between the on-off valve 32 and the on-off valve 55) is at the initial pressure, that is, the portion upstream of the on-off valve 55 in the closed state (mainly the reserve tank 54). ), The refrigerant gas having the pressure for the previous period is stored. From this state, when the on-off valve 55 is opened, the refrigerant gas between the on-off valve 32 and the on-off valve 55 is caused to flow into the cooling chamber 3 by the first-stage passage 50 due to a differential pressure with respect to the vacuum state (pressure p0). To be introduced.

  As described above, in the present embodiment, the first-stage passage 50 is used, the opening / closing valve 55 of the first-stage passage 50 is closed, and a boosting unit is provided in a portion upstream of the opening / closing valve 55 in the first-stage passage 50. 33 is used, and the opening and closing valve 55 is opened from the state in which the amount of refrigerant gas corresponding to the first pressure is stored, whereby the refrigerant gas introduction process is performed.

  The setting of the pressure for the first period is performed based on the volume of the cooling chamber 3, the length / pipe diameter of the passage 50 for the first period, the volume of the reserve tank 54, and the like, as in the first embodiment. That is, the state in which the refrigerant gas of the previous pressure is stored in the upstream portion of the opening / closing valve 55 in the previous passage 50 corresponds to the state in which the amount of the refrigerant gas corresponding to the first pressure is stored. .

  Further, in the piping configuration in which the branch gas introduction passage 70 is provided as described above, the opening / closing valve 55 is opened during the refrigerant gas introduction process, so that the passage 50 for the previous period is moved downstream from the opening / closing valve 55. A part of the flowing refrigerant gas is introduced into the motor housing 17 through the branch gas introduction passage 70. Thereby, similarly to the case where the branch gas introduction passage 40 is provided in the first embodiment, the pressure in the motor housing 17 can be efficiently increased to the first pressure.

  In the apparatus configuration of the present embodiment, the late refrigerant gas introduction process (S23) is performed as follows. That is, the late passage 60 is used in the late refrigerant gas introduction process. That is, in the late refrigerant gas introduction process, the refrigerant gas supplied from the supply source 31 and boosted by the booster unit 33 is introduced into the late passage 60 side. Therefore, in the latter-stage refrigerant gas introduction process, introduction of the refrigerant gas to the first-stage passage 50 side is restricted by an open / close valve (not shown) or the like.

  In the latter-stage refrigerant gas introduction process, the pressure due to the refrigerant gas upstream of the first on-off valve 35 in the latter-stage passage 60 is set as the latter-stage pressure while the first on-off valve 35 is closed. That is, with the first opening / closing valve 35 closed, the pressure of the refrigerant gas from the supply source 31 is increased by the boosting unit 33, and the upstream side of the first opening / closing valve 35 (the boosting unit 33 and the reserve tank). 34) is the late pressure. Here, the refrigerant gas having the upstream pressure upstream from the first on-off valve 35 is mainly stored in the reserve tank 34 on the upstream side of the first on-off valve 35. In addition, the state where the upstream side of the first opening / closing valve 35 is set to the late pressure is ensured by the opening / closing valve 32.

  Thus, the upstream side of the first on-off valve 35 (between the on-off valve 32 and the first on-off valve 35) is in the late pressure, that is, the upstream side of the closed first on-off valve 35. The refrigerant gas having the late pressure is stored in (mainly the reserve tank 34). From this state, the first on-off valve 35 is opened, so that the refrigerant gas between the on-off valve 32 and the first on-off valve 35 is cooled by the late passage 60 by the differential pressure with respect to the first pressure. 3 is introduced.

  Thus, in the present embodiment, the late passage 60 is used, the first on-off valve 35 is in a closed state, and the booster unit 33 is used on the upstream side of the first on-off valve 35. From the state where the amount of refrigerant gas corresponding to the second pressure is stored, the first on-off valve 35 is opened, so that the late refrigerant gas introduction process is performed.

  The latter-stage pressure is set based on the volume of the cooling chamber 3, the length / pipe diameter of the latter-stage passage 60, the volume of the reserve tank 34, and the like, as in the first embodiment. In other words, the state in which the refrigerant gas of the late pressure is stored in the portion upstream of the first opening / closing valve 35 in the late passage 60 is the state in which the amount of the refrigerant gas corresponding to the second pressure is stored. Equivalent to.

  As described above, according to the present embodiment in which the first-stage refrigerant gas introduction process and the second-stage refrigerant gas introduction process are performed by separate piping configurations, the set pressure difference for the refrigerant gas pressure is large (usually different by about two digits). With respect to the first-stage refrigerant gas introduction process and the second-stage refrigerant gas introduction process, it is easy to ensure the stability of the refrigerant gas pressure in each process.

  By the way, in the gas cooling of the workpiece 1 performed by the apparatus configuration of the present embodiment, the fan acceleration time (fan start-up process) is related to the limit of the starting current of the electric motor 15 and the harmonics generated by the driving of the electric motor 15. In some cases, it may not be possible to shorten the time sufficiently. That is, in order to increase the cooling rate in gas cooling, the fan acceleration time may be shortened. However, the shortening of the fan acceleration time causes harmonics and noise accompanying the increase of the starting current of the electric motor 15. Generation of harmonics or the like may affect not only the equipment including the electric motor 15 but also peripheral equipment.

  As described above, when the fan acceleration time cannot be sufficiently shortened, the temperature of the workpiece 1 (hereinafter referred to as “work temperature”) decreases during the fan acceleration time, and sufficient cooling is performed in the gas cooling. There are times when speed cannot be obtained. Insufficient cooling rate in gas cooling can cause quenching quality to deteriorate, such as insufficient quenching and insufficient hardness.

  Therefore, in the heat treatment method of the present embodiment, the work temperature before the refrigerant gas introduction process is reduced to the temperature drop amount of the work 1 that is lowered during the fan starting process (hereinafter referred to as “work temperature drop amount”). It is preferable that it is raised in advance by a corresponding amount.

  Specifically, the amount of decrease in the workpiece temperature during the fan acceleration time is measured in advance by experiments or the like. The workpiece temperature reduction amount is measured by measuring the workpiece temperature reduction amount in the fan starting process performed after the refrigerant gas introduction process in the same manner as when the workpiece 1 is actually cooled by the heat treatment method as described above. Is done.

  In the measurement of the amount of decrease in the workpiece temperature, a predetermined temperature (hereinafter referred to as “workpiece reference temperature”) set in advance for the workpiece temperature immediately before cooling after the vacuum heating in the heating chamber 2 (before the previous refrigerant gas introduction process is performed). ) Is the standard. That is, in the measurement of the workpiece temperature decrease amount, the temperature decrease amount from the workpiece reference temperature is measured. As the measurement of the work temperature drop, direct measurement by measuring the temperature drop of the work 1 itself or indirect measurement by measuring the ambient temperature of the cooling chamber 3 in which the work 1 is set is performed. Is called.

  Then, the workpiece temperature is raised by the amount of the workpiece temperature decrease measured in advance. The workpiece temperature raised here is the workpiece temperature immediately before cooling after the vacuum heating in the heating chamber 2. For example, when the workpiece temperature decrease amount is 50 ° C., the workpiece temperature is raised by 50 ° C. from the workpiece reference temperature. The workpiece temperature is raised by adjusting the heating temperature of the workpiece 1 by heating means such as a graphite heater provided in the heating chamber 2.

  As described above, when the workpiece 1 is cooled with the gas, the workpiece temperature is increased in advance, so that it is possible to prevent a sufficient cooling rate from being obtained due to the decrease in the workpiece temperature during the fan acceleration time. In other words, since the workpiece temperature is raised in advance, even if the workpiece temperature is lowered during the fan acceleration time, the temperature reduction margin at the time of quenching the workpiece 1 is secured, so that a sufficient cooling rate can be obtained. .

Further, the workpiece temperature decrease amount ΔT _w (° C.) can be estimated based on the following equation (1).
ΔT _w = {Q · t (T _f −T _s ) α} / A + T _s (1)

In the above formula (1), Q is the average air volume (Nm ³ / min) during the fan starting process, t is the time (sec) of the fan starting process, and T _s is the refrigerant gas temperature (° C.) at the start of the fan starting process. , T _f is the temperature (° C.) of the refrigerant gas at the end of the fan starting process, α is the specific heat of the refrigerant gas, and A is the heat dissipation coefficient of the workpiece 1 obtained in advance.

Here, the specific heat α of the refrigerant gas is a known eigen constant depending on the type of the refrigerant gas. The heat dissipation coefficient A of the work 1 is a specific constant determined based on the heat capacity of the tray 8 or other jig on which the work 1 is set or the work 1 itself, the shape of the work 1, the other equipment structure, etc. It is a value that can be obtained in advance through experiments or the like. In addition, for the average air volume Q during the fan starting process, the value indicated by Nm ³ is the normal value for the volume of the gas, and the value of the gas converted as the value in the state of temperature 0 ° C., atmospheric pressure 760 mmHg, humidity 0%. Volume. Also, the time t (sec) of the fan starting process corresponds to the fan acceleration time. Therefore, hereinafter, t is a fan acceleration time. In addition, the temperature T _s of the refrigerant gas at the start of the fan start-up process as a "starting point temperature", the temperature T _f of the refrigerant gas at the time of fan start-up process termination and "at the end of temperature."

The above formula (1) is derived from the following formula (2).
Q · t (T _f −T _s ) α = A (ΔT _w −T _s ) (2)

  The above formula (2) is based on the viewpoint that the amount of heat for cooling the workpiece 1 is equal to the amount of heat reduced in the workpiece 1 to be cooled in gas cooling. The above formula (1) is derived by modifying the above formula (2).

Then, when calculating the work temperature decrease [Delta] T _w according to the above formula (1), as a starting point temperature T _s, at the start of the fan starting process, i.e. when the rotation of the fan 16 is started (FIG. 2, reference time t1 ) In the cooling chamber 3 is measured. The average air volume Q and the fan acceleration time t are from the start of the fan start process (see time t1 in FIG. 2) to the time when the fan speed reaches the set speed (see time t2 in the same figure). The average blast volume and elapsed time (time from time t1 to time t2) are measured. Further, as the end temperature _Tf , the ambient temperature in the cooling chamber 3 at the end of the fan starting process, that is, when the fan rotation speed reaches the set rotation speed (see time t2 in FIG. 2) is measured.

Moreover, an example of the experimental result is shown below about the thermal radiation coefficient A of the workpiece | work 1 which is a value calculated | required by experiment etc. as mentioned above. In the present experimental result example, the following measurement results were obtained as measurement values for each value such as the starting temperature T _s measured as described above. That is, ΔT _w = 50 (° C.), T _s = 30 (° C.), T _f = 50 (° C.), t = 1.0 (sec), Q = 210 (Nm ³ / min). As for α, when nitrogen gas is used as the refrigerant gas, α = 1.04 (kJ / kg · K).

On the other hand, the above equation (2) can be transformed as the following equation (3).
A = {Q · t (T _f −T _s ) α}} / (ΔT _w −T _s ) (3)

Therefore, A = 218.4 is calculated by substituting each value according to the measurement result in the above experimental result example into the above equation (3). Then, in this way the radiation coefficient A of the workpiece 1 that is calculated is used for calculation of the work temperature decrease [Delta] T _w according to the above formula (1). That is, in the above equation (1), from the measured values for the values such as the heat dissipation coefficient A = 218.4 of the work 1, the specific heat α of the refrigerant gas, and the starting temperature T _s measured as described above, the work temperature decrease [Delta] T _w is calculated.

Thus, the work temperature decrease [Delta] T _w, by estimating a value calculated by the equation (1), it is easy to determine the workpiece temperature decrease [Delta] T _w. That is, upon determining the workpiece temperature decrease [Delta] T _w, by the equation (1) is used, the work temperature decrease [Delta] T _w which varies variously by a change in various conditions in the gas cooling the workpiece 1, facilitates the derivation It becomes.

  Further, by using the above formula (2), when the workpiece temperature is raised in advance during the gas cooling of the workpiece 1 as described above, the fan acceleration time t corresponding to the raised temperature can be obtained. That is, in the case where the workpiece temperature is increased in advance and in the case where the workpiece temperature is not increased, under the condition that the workpiece temperature is the same when the fan acceleration time t has elapsed, the case where the workpiece temperature is increased in advance is The fan acceleration time t becomes longer. In other words, when the workpiece temperature is raised in advance, the time from when the fan 16 is started until the workpiece temperature is lowered to a predetermined temperature is increased.

Thus, when the workpiece temperature is raised in advance, the fan acceleration time t that changes in response to the change in the temperature change amount to be raised (hereinafter referred to as “work temperature rise amount”) is expressed by the following equation (4). Presumed.
t = {A (ΔT _wa −T _s )} / {Q (T _f −T _s ) α} (4)

In the above formula (4), [Delta] T _wa is the sum of the workpiece temperature rise amount at the time of raising the measured value and the work temperature of the workpiece decreased temperatures [Delta] T _w to a predetermined target temperature. In other words, [Delta] T _wa corresponds to the work temperature decrease [Delta] T _w when the work temperature is raised to a predetermined target temperature.

When the fan acceleration time t is estimated by the above equation (4), the workpiece temperature that is raised in advance when the workpiece 1 is gas-cooled is set in advance as a predetermined target temperature T _m (° C.). Target temperature T _m which is set here, the heat treatment quality of the work 1 (e.g., grain size, fatigue strength, partial melting, etc.) is determined based on the upper limit value or the like which is defined in order to ensure.

The estimation of the fan acceleration time t according to the above formula (4) will be described by taking as an example a case where the target temperature _Tm is 950 ° C. and the workpiece temperature increase is 50 ° C. In this case, the workpiece reference temperature T _b (° C.) before being raised in advance is 950−50 = 900 (° C.). Then, using the measurement results obtained in the above experimental example results, ΔT _wa = ΔT _w + (workpiece temperature _{increase: T m -T b) = 50} (℃) + (950-900) (℃) = 100 (° C).

Then, if the value of _ΔTwa calculated as described above and the measurement result obtained in the above experimental result example are substituted into the above equation (4), t = 3.5 (sec) is obtained. That is, t = 3.5 (sec) obtained in this case is a fan acceleration when the workpiece temperature is raised to the target temperature T _m (950 ° C.) in advance and the workpiece temperature drop amount ΔT _w = 50 ° C. It corresponds to time.

That is, under the condition that the workpiece temperature is the same when the fan acceleration time t has elapsed, that is, the workpiece temperature reduction amount ΔT _w = 50 (° C.), the workpiece temperature is raised in advance (workpiece temperature). by but the target temperature T _{m (950} ° C.) are), in comparison with the case where the work temperature is not raised when (workpiece temperature is work reference temperature T _{b (900} ° C.) a), fan acceleration time The time is increased from 1 sec to 3.5 sec. In other words, regarding the measurement results obtained in the above experimental result example, the workpiece temperature before the refrigerant gas introduction process is changed from the workpiece reference temperature T _b (900 ° C.) to the target temperature T _m (950 ° C.). Raising the speed corresponds to delaying the fan acceleration time t from 1 sec to 3.5 sec.

Thus, in the heat treatment method of the present embodiment, workpiece temperature before year refrigerant gas introduction process is performed, when raised to a predetermined target temperature T _m which is set in advance, it performs year refrigerant gas introduction process Previous work temperature is the target temperature T corresponds to rise _m fan acceleration time t (time of the fan starting process) is estimated based on the equation (4).

  As described above, since the fan acceleration time can be estimated, for example, when the equipment for performing the heat treatment method of the present embodiment is moved to another factory or the like, the work 1 is changed uniformly. For various conditions, it is possible to shorten the lead time for setting conditions.

  For example, in order to increase the cooling rate in gas cooling, the fan acceleration time may be shortened. However, shortening the fan acceleration time may have a limit due to the relationship with the harmonics accompanying the increase in the starting current of the electric motor 15 as described above. In addition, the presence or absence of the occurrence of harmonics or the like often cannot be found unless the equipment for performing the heat treatment method is actually operated at the site. Furthermore, as described above, the generation of harmonics and the like may affect not only the equipment equipped with the motor 15 but also the peripheral equipment. Therefore, when harmonics or the like are generated, it is necessary to take immediate measures. .

  Therefore, for example, when it is desired to reduce the starting current of the motor 15 in order to prevent the generation of harmonics, when the workpiece temperature is raised in advance to ensure the workpiece temperature before the late refrigerant gas introduction process is performed. As described above, the fan acceleration time (t) is estimated by the above equation (4).

  That is, reducing the starting current of the electric motor 15 corresponds to delaying (extending) the fan acceleration time. For this reason, when reducing the starting current of the motor 15 in order to prevent the generation of harmonics, according to the method using the above equation (4), how much fan acceleration is required in relation to the workpiece temperature that is raised in advance. It can be estimated whether to slow down the time. As described above, the fan acceleration time can be estimated in relation to the workpiece temperature in the case of the occurrence of harmonics that require immediate countermeasures. This is extremely effective for shortening.

  The above example relates to a case where the workpiece temperature is raised in advance and the fan acceleration time is delayed. However, the above equation (2) is used in a modified manner to adjust other factors. Can also be used. For example, a change in the motor 15, a variation in the manufacturing accuracy of the motor 15, a variation in the refrigerant gas pressure, a change in the type of the refrigerant gas, or a discharge condition of the motor 15 that changes in accordance with these changes (represented by the Paschen curve described above) With the change of various conditions such as the above, it is possible to adjust the heating temperature of the workpiece 1 and the fan acceleration time each time by using the above formula (2) by modifying it. As described above, by adjusting the heating temperature of the workpiece 1 and the fan acceleration time according to changes in various conditions, the gas is generated by the convection of the refrigerant gas by the rotation of the fan 16 driven by the electric motor 15. It becomes possible to contribute to energy saving in cooling.

  Further, in the above-described embodiment of the present invention, as the configuration of the heat treatment apparatus for performing the heat treatment method, one having a two-chamber structure including the heating chamber 2 and the cooling chamber 3 is adopted. It is not limited to. That is, the heat treatment method according to the present invention can be applied to a heat treatment apparatus having a one-chamber structure in which the heating chamber 2 and the cooling chamber 3 are configured as a common processing chamber.

The figure which shows the whole structure of the heat processing apparatus which concerns on one Embodiment of this invention. The figure which shows the graph of the time change of the refrigerant gas pressure and fan rotation speed in the gas cooling which concerns on one Embodiment of this invention. The flowchart which shows the heat processing method which concerns on one Embodiment of this invention. The figure which shows the graph of the time change of the refrigerant gas pressure and fan rotation speed in the gas cooling which concerns on the conventional method. The figure which shows the example of an experimental result showing the comparison with a present Example and a prior art example in the relationship between fan acceleration time and the hardness of a hardened product. The figure which shows the whole structure of the heat processing apparatus which concerns on another embodiment of this invention.

Explanation of symbols

1 Workpiece (object to be processed)
2 Heating chamber 3 Cooling chamber (processing chamber)
DESCRIPTION OF SYMBOLS 15 Electric motor 16 Fan 17 Motor housing 18 Inlet duct 19 Outlet duct 30 Gas introduction passage 31 Supply source 33 Boosting unit 34 Reserve tank 35 1st on-off valve (1st on-off valve means, on-off valve means)
38 Second on-off valve (second on-off valve means)
40 Branch gas introduction passage 50 First passage (first gas introduction passage)
54 Reserve tank 55 Open / close valve (open / close valve means)
60 Late passage (second gas introduction passage)
70 Branch gas introduction passage

Claims (7)

A heat treatment method in which a heated object to be processed is cooled by convection of a refrigerant gas by a fan having a motor as a drive source provided in a space communicating with the process chamber in a processing chamber containing the object to be processed. There,
Introducing the refrigerant gas into the processing chamber so that the pressure in the processing chamber becomes a first pressure set in advance as a low pressure such that discharge in the electric motor does not occur;
In a state where the pressure in the processing chamber is the first pressure, the electric motor is started, and the rotational speed of the electric motor is increased to a predetermined rotational speed that is set in advance in relation to the driving of the fan. Fan starting process,
In a state where the rotational speed of the electric motor is the predetermined rotational speed, the refrigerant gas is set in advance in the processing chamber, and the pressure in the processing chamber is preset as a pressure used for cooling the object to be processed. And a late refrigerant gas introduction process for introducing the pressure so as to become pressure,
The gas introduction passage provided in order from the upstream side to the downstream side in the refrigerant gas introduction direction in a gas introduction passage which is a passage for introducing the refrigerant gas supplied from a predetermined supply source into the processing chamber. The first opening / closing valve means for opening and closing the second opening / closing valve means for opening and closing,
The first on-off valve means and the second on-off valve means are in a closed state, and a portion of the gas introduction passage between the first on-off valve means and the second on-off valve means is From the state in which the amount of the refrigerant gas corresponding to the first pressure is stored, by opening the second on-off valve means, the previous refrigerant gas introduction process is performed,
The first on-off valve means is in a closed state and the second on-off valve means is in an open state, and the second inlet on the upstream side of the first on-off valve means in the gas introduction passage A heat treatment method characterized in that the second refrigerant gas introduction process is performed by opening the first on-off valve means from a state where the amount of the refrigerant gas corresponding to the pressure is stored.   2. The heat treatment method according to claim 1, wherein a branch gas introduction passage that branches from the gas introduction passage and communicates with the space in which the electric motor is provided is provided on the downstream side of the first on-off valve means. . A heat treatment method in which a heated object to be processed is cooled by convection of a refrigerant gas by a fan having a motor as a drive source provided in a space communicating with the process chamber in a processing chamber containing the object to be processed. There,
Introducing the refrigerant gas into the processing chamber so that the pressure in the processing chamber becomes a first pressure set in advance as a low pressure such that discharge in the electric motor does not occur;
In a state where the pressure in the processing chamber is the first pressure, the electric motor is started, and the rotational speed of the electric motor is increased to a predetermined rotational speed that is set in advance in relation to the driving of the fan. Fan starting process,
In a state where the rotational speed of the electric motor is the predetermined rotational speed, the refrigerant gas is set in advance in the processing chamber, and the pressure in the processing chamber is preset as a pressure used for cooling the object to be processed. And a late refrigerant gas introduction process for introducing the pressure so as to become pressure,
A first gas introduction passage which is the gas introduction passage for performing the previous refrigerant gas introduction process as a gas introduction passage which is a passage for introducing the refrigerant gas supplied from a predetermined supply source into the processing chamber. And a second gas introduction passage that is the gas introduction passage for performing the latter-stage refrigerant gas introduction process,
According to a configuration including opening / closing valve means provided in each of the first gas introduction passage and the second gas introduction passage, for opening and closing the gas introduction passage,
The first gas introduction passage is used, the on-off valve means of the first gas introduction passage is closed, and the introduction direction of the refrigerant gas is more than the on-off valve means in the first gas introduction passage. From the state where the amount of the refrigerant gas corresponding to the first pressure is stored in the upstream portion of the first gas introduction passage, the opening / closing valve means of the first gas introduction passage is opened, thereby the first refrigerant gas Perform the introduction process,
Using the second gas introduction passage, the on-off valve means of the second gas introduction passage is in a closed state, and in the portion upstream of the on-off valve means in the second gas introduction passage, The second refrigerant gas introduction process is performed by opening the on-off valve means of the second gas introduction passage from a state where the refrigerant gas corresponding to the second pressure is stored. A heat treatment method.   A branch gas introduction passage branched from the first gas introduction passage and communicating with the space in which the electric motor is provided is provided on the downstream side of the on-off valve means of the first gas introduction passage. The heat treatment method according to claim 3.   The temperature of the object to be processed before performing the preceding refrigerant gas introduction process is increased in advance by an amount corresponding to the amount of temperature decrease of the object to be processed that decreases during the fan starting process. 5. The heat treatment method according to any one of 4 above. The heat treatment method according to claim 5, wherein the temperature decrease amount is estimated based on the following equation.
ΔT _w = {Q · t (T _f −T _s ) α} / A + T _s
Where ΔT _{w is the} amount of temperature decrease, Q is the average air volume during the fan start process, t is the time of the fan start process, T _{s is} the temperature of the refrigerant gas at the start of the fan start process, and T _{f is} : The temperature of the refrigerant gas at the end of the fan starting process, α: the specific heat of the refrigerant gas, and A: the heat dissipation coefficient of the workpiece to be obtained in advance. When raising the temperature of the object to be processed before performing the previous refrigerant gas introduction process to a predetermined target temperature set in advance,
The time for the fan starting process corresponding to raising the temperature of the object to be processed before the refrigerant gas introduction process to the target temperature is estimated based on the following equation. The heat processing method as described in any one of -4.
t = {A (ΔT _wa −T _s )} / {Q (T _f −T _s ) α}
Here, t: time of the fan starting process, A: heat dissipation coefficient of the object to be processed obtained in advance, ΔT _wa : measured value of temperature decrease amount of the object to be processed that decreases during the fan starting process, and the object to be processed Sum of temperature rise when raising the temperature of the workpiece to the target temperature, T _s : temperature of the refrigerant gas at the start of the fan starting process, Q: average air volume during the fan starting process, T _f : The temperature of the refrigerant gas at the end of the fan starting process, α: the specific heat of the refrigerant gas.

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