JP2014118606A - Heat treatment apparatus and heat treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment apparatus and a heat treatment method which can reduce heat treatment cost by shortening the time for carbonitriding treatment.SOLUTION: A heat treatment apparatus 1 includes a carburization treatment chamber 5 for carburizing a work-piece 2 made of steel and a nitriding treatment chamber 6 for nitriding the work-piece 2 separately. In the heat treatment apparatus 1 in which the work-piece 2 carburized in the carburization treatment chamber 5 is transported to the nitriding treatment chamber 6 and then is nitrized, the heat treatment apparatus 1 is configured such that the carburization treatment chamber 5 and the nitriding treatment chamber 6 are arranged mutually separately and the work-piece 2 is nitrized in the nitriding treatment chamber 6 utilizing excess heat of the work-piece 2 after the work-piece 2 is carburized in the carburization treatment chamber 5.

Description

  The present invention relates to a heat treatment apparatus for carburizing and nitriding a steel member, and a heat treatment method therefor.

  Conventionally, in order to improve the wear resistance and fatigue strength of steel parts such as gears and shafts, heat treatment such as carburizing and carburizing and nitriding (or carbonitriding) has been performed. Carburizing is a surface treatment method in which carbon enters the surface of a steel material to enter and dissolve and harden only the surface layer of the steel material. In addition, carburizing and nitriding is aimed at further improving the effect of surface modification by carburizing, and is a surface treatment method in which nitrogen is infiltrated into the steel surface together with carbon to harden the surface layer of the steel material. .

  An example of the invention related to the carburizing and nitriding treatment as described above is described in Patent Document 1. The heat treatment apparatus described in Patent Document 1 includes a carburizing zone, a cooling zone, and a nitriding zone that are partitioned by a series of passages being sequentially partitioned by an opening / closing door, and the series of objects to be processed is the above-described series. It has the structure provided with the transfer means which transfers sequentially along this path | route, and the forced cooling means which cools a to-be-processed object in a cooling zone.

  Specifically, the heat treatment apparatus described in Patent Document 1 is configured such that a pallet loaded with workpieces is sequentially transferred by a power roller inside a tunnel-type continuous furnace having a series of passages. Has been. The continuous furnace is partitioned for each process by a plurality of open / close doors, and a degreasing chamber, a heating chamber, a carburizing chamber, a cooling chamber, a reheating chamber, a descending chamber, a nitriding chamber, and an extraction zone are provided in the order of the processes. Yes. Therefore, in the heat treatment apparatus described in Patent Document 1, first, the workpiece is degreased in the degreasing chamber. The degreased object to be treated is transferred to a heating chamber having a room temperature of about 900 to 950 ° C. and preliminarily heated, and then transferred to a carburizing chamber having a room temperature of about 900 to 950 ° C. In the carburizing chamber, carbon is diffused and permeated into the surface of the workpiece by supplying acid carburizing gas. That is, the workpiece is carburized. The carburized workpiece is transferred to the cooling chamber and is forcedly cooled by blowing cooling gas. In this cooling chamber, since the workpiece is rapidly cooled by the cooling gas, the same effect as that obtained when quenching the workpiece after carburizing can be obtained.

  The object to be processed cooled in the cooling chamber after carburizing is transferred to a re-heating chamber having a room temperature of about 850 to 870 ° C. and heated again, and then transferred to a descending greenhouse. In the descending greenhouse, the temperature of the object to be treated is lowered to about 820 to 840 ° C. in order to properly carbonitride the object to be treated, and acid carburizing gas and ammonia gas are supplied in the course of the temperature reduction. Thus, the object to be treated is carbonitrided. And a to-be-processed object is transferred to a nitriding chamber, and is hold | maintained under the temperature of about 820-840 degreeC in the carbonitriding gas atmosphere similar to a greenhouse. Thereby, a to-be-processed object is carbonitrided in earnest. Thereafter, the object to be processed is transferred to the salt tank through the extraction zone, and quenched under a predetermined cooling condition.

JP-A-5-5171

  As described above, the heat treatment apparatus described in Patent Document 1 is configured such that a series of processing operations of carburizing, cooling, and nitriding can be performed in a continuous furnace partitioned by an open / close door. Further, the workpiece is forcibly cooled in the cooling zone after the carburizing treatment. Therefore, it is said that a series of processing operations can be performed efficiently and without energy loss, and the time required for cooling the workpiece can be saved.

  However, in the heat treatment apparatus described in the above-mentioned Patent Document 1, after carburizing the workpiece in the carburizing chamber, the workpiece is once cooled in the cooling chamber, and further in the re-heating chamber and descending chamber. Nitriding is performed after repeatedly raising and lowering the temperature of the processed material. Therefore, a long time is required for the series of processing.

  On the other hand, as one of the measures for shortening the treatment time of the carburizing and nitriding treatment, there is an increase in the carburizing treatment temperature. For example, by performing carburization normally performed at about 900 to 950 ° C. at a high temperature of about 1100 ° C., it is possible to improve the carbon diffusion rate with respect to the steel material and shorten the carburization processing time. However, when nitriding is carried out continuously at the same time as the carburization at such a high temperature or in the same furnace as the carburizing, the ammonia gas supplied for nitriding is at a high temperature of 1000 ° C. or higher. It is almost decomposed on the heater in the furnace. For this reason, ammonia gas cannot reach the surface of the steel material to be nitrogenized, and proper nitrogenization cannot be performed. In order to avoid the decomposition of the ammonia gas on the heater and perform proper nitriding, it is necessary to lower the temperature of the furnace and the heater to about 850 ° C. or less.

  Thus, in order to shorten the processing time when carburizing and nitriding the steel material and to reduce the heat treatment cost, there are various problems as described above, and there is still room for improvement.

  This invention was made paying attention to said technical subject, and provides the heat processing apparatus and heat processing method which can shorten the processing time at the time of carburizing and nitriding steel materials, and can aim at reduction of heat processing cost. It is for the purpose.

  In order to achieve the above object, the invention of claim 1 is provided with a carburizing chamber for carburizing a steel workpiece and a nitriding chamber for nitriding the workpiece separately, and carburizing in the carburizing chamber. In the heat treatment apparatus for transferring and nitriding the work that has been caused to move into the nitriding treatment chamber, the carburizing treatment chamber and the nitriding treatment chamber are configured to be separated from each other, and in the nitriding treatment chamber, The heat treatment apparatus is configured to nitrify the work by using residual heat of the work after carburizing in a carburizing chamber.

  According to a second aspect of the present invention, there is provided a nitriding gas supply means for filling the nitriding treatment chamber with a nitriding gas for nitriding the workpiece into the nitriding treatment chamber. Provided in the nitriding treatment chamber, the nitriding gas supplied by the nitriding gas supply means is brought into contact with the workpiece having the remaining heat, thereby nitriding the workpiece. It is the heat processing apparatus characterized by the above-mentioned.

On the other hand, the invention of claim 3 is a heat treatment method for carburizing and nitriding a steel work, and a heating step for heating to a temperature higher than a carburizing temperature at which the work can be carburized, and a temperature of the work. Carburizing gas for carburizing the work is brought into contact with the work heated to the carburizing temperature or higher in the temperature raising step in a carburizing chamber provided with a heater capable of being maintained at the carburizing temperature or higher. Carburizing the workpiece into the workpiece having a residual heat equal to or lower than the carburizing temperature after carburizing in the carburizing step in a carburizing step of carburizing the workpiece and in a nitriding chamber separated from the carburizing chamber. And a nitriding step of nitriding the workpiece by bringing a nitriding gas into contact therewith.

  According to the present invention, the carburizing step for carburizing the workpiece and the nitriding step for nitriding the workpiece are each performed in a processing chamber separated from each other. That is, the workpiece carburized in the carburizing chamber is then transferred to a nitriding chamber that is separate from the carburizing chamber, and is nitrogenated in the carburizing chamber. In the nitriding treatment chamber, nitriding is performed by utilizing the residual heat of the workpiece after carburizing without heating the workpiece. For this reason, it is possible to avoid raising the temperature of the work again because of nitriding after carburizing, and it is possible to shorten the processing time when carburizing and nitriding the work, and as a result, the heat treatment cost can be reduced.

It is a schematic diagram for demonstrating the outline | summary of a structure of the heat processing apparatus which concerns on this invention, and an example of the process process of the carburizing nitrousation implemented using the heat processing apparatus. It is a figure for demonstrating the test result at the time of carburizing and nitriding a steel test piece by applying the heat treatment apparatus and heat treatment method concerning this invention, and is a time chart which shows the heat pattern at the time of the heat treatment . It is a figure for demonstrating the test result at the time of carburizing and nitriding a steel test piece by applying the heat treatment apparatus and heat treatment method concerning this invention, and is a figure showing the hardness test result of the test piece after the heat treatment It is. It is a figure for demonstrating the test result at the time of carburizing and nitriding a steel test piece by applying the heat treatment apparatus and heat treatment method concerning this invention, and shows the fatigue strength test result of the test piece after the heat treatment FIG.

  Next, the present invention will be specifically described with reference to the drawings. The outline of the configuration of the heat treatment apparatus according to the present invention is shown in FIG. A heat treatment apparatus 1 shown in FIG. 1 is an apparatus and equipment for performing carbonitriding (or carbonitriding) on a steel workpiece 2 that is a material to be heat treated. The heat treatment apparatus 1 is provided with a container and a treatment chamber independently for each series of heat treatment steps. That is, the heat treatment apparatus 1 includes a transfer cell 3 that accommodates a workpiece 2 that has been carried in, a heating chamber 4 that heats the workpiece 2, a carburization treatment chamber 5 that carburizes the workpiece 2, and a nitriding treatment that nitriding (nitriding) the workpiece 2. A chamber 6 and a cooling chamber 7 for quenching the workpiece 2 are provided.

  The workpiece 2 is a machine part, an automobile part, or the like that is processed or molded using low carbon steel, low carbon alloy steel, or the like as a material. For example, the carburizing and nitriding treatment according to the present invention is performed on a workpiece 2 such as a gear, a rotary shaft, or a bearing that requires high wear resistance and fatigue strength.

  The transfer cell 3 is configured as a pressure vessel capable of receiving and storing the work 2 from a predetermined opening (not shown) and holding the work in an airtight state by closing the opening. . And the inside of a container is vacuum-sucked from a predetermined suction port (not shown), and while maintaining the state where the inside of a container was pressure-reduced, it can be conveyed with the pressure-reduced state.

  The heating chamber 4 is a high-frequency heating furnace in which a heating coil 4a is provided and uses the principle of induction heating. And while being able to hold | maintain the inside of a furnace in a pressure reduction state, it is comprised so that it can connect with the opening part of said conveyance cell 3, and the pressure reduction state being hold | maintained. Therefore, the work 2 can be transported from the inside of the container of the transported cell 3 that has been decompressed into the furnace of the heating chamber 4 while maintaining the decompressed state. And it is comprised so that the workpiece | work 2 can be heated up to about 900-1200 degreeC by supplying with electricity to the heating coil 4a.

  The carburizing chamber 5 is a processing chamber or a processing furnace that performs carburizing to infiltrate and dissolve carbon into the surface layer of the heated workpiece 2. In this embodiment, the heater 5a is provided so that the atmospheric temperature in the room (inside the furnace) can be maintained at about 1000 to 1100 ° C. In addition, the carburizing chamber 5 is provided with a gas injection nozzle 5b for filling a carburizing gas such as a hydrocarbon gas into the chamber. Further, similarly to the heating chamber 4, the carburizing chamber 5 can hold the chamber in a reduced pressure state and can be connected to the opening of the transfer cell 3 while maintaining the reduced pressure state. It is configured as follows. Therefore, the work 2 is carried into the carburizing chamber 5 from the inside of the container of the transported cell 3 that has been decompressed, and the workpiece 2 is transferred from the carburizing chamber 5 to the transport cell 3 while being in the decompressed state. It has a configuration that can be carried out. The carburizing chamber 5 is provided so as to be thermally insulated from the nitriding chamber 6.

  In general, carburizing by a gas carburizing method using a carburizing gas is performed at a carburizing temperature of about 900 to 950 ° C. However, in some cases, for example, a carburizing temperature of 900 ° C. or lower is used to reduce the carburizing depth. Or in order to shorten processing time, it may implement at the high temperature of 1000 degreeC or more. Carburization is performed at a high temperature of 1000 ° C. or higher, thereby increasing the diffusion rate of carbon that enters and dissolves in the surface layer of the work 2 and shortens the carburization time. As described above, the carburizing chamber 5 is configured to be able to carburize the workpiece 2 by filling the chamber with a carburizing gas in a state where the atmospheric temperature in the room is maintained at a high temperature of about 1000 to 1100 ° C. Yes. Therefore, in the heat treatment apparatus 1 according to the present invention including the carburizing chamber 5 as described above, the workpiece 2 can be carburized in a shorter processing time than usual.

  The nitriding treatment chamber 6 is a treatment chamber or a treatment furnace that performs nitriding (nitriding) that causes nitrogen to enter and dissolve into the surface layer of the heated workpiece 2. The nitriding treatment chamber 6 in the present invention is for performing nitriding by using the residual heat of the work 2 heated for carburizing, and raises the temperature of the work 2 or maintains the temperature of the work 2. Therefore, a heater or the like is not provided. Therefore, it is configured as a thermal insulation room or a thermal insulation furnace that is isolated from the outside and insulated. The nitriding treatment chamber 6 is provided with a gas injection nozzle 6a for filling a nitriding gas such as ammonia gas into the room (inside the furnace). In order to further promote the carburization of the workpiece 2 in the nitriding treatment chamber 6, a gas injection nozzle for filling the carburizing gas into the chamber can be provided. Or it can also comprise so that carburizing gas may be injected with nitriding gas from said gas injection nozzle.

  In addition, the nitriding treatment chamber 6 can hold the interior of the chamber in a reduced pressure state as well as the heating chamber 4 and the carburizing treatment chamber 5, and also maintains the reduced pressure state of the opening of the transfer cell 3 described above. It is comprised so that it can connect as it is. Therefore, the work 2 is carried into the nitriding treatment chamber 6 from the container of the depressurized transfer cell 3 in the reduced pressure state, and the work 2 is transferred from the nitriding treatment chamber 6 in the reduced pressure state. 3 can be carried out. As described above, the nitriding treatment chamber 6 is provided so as to be thermally insulated from the carburizing treatment chamber 5.

  In general, nitriding by a gas nitriding method using a nitriding gas is performed at a nitriding temperature of about 500 to 600 ° C. Here, ammonia gas normally used as a nitriding gas is decomposed at a temperature of about 850 ° C. or higher. Therefore, suppose that nitriding was performed using ammonia gas in the carburizing chamber 5 described above, by supplying ammonia gas to the carburizing chamber 5 after carburizing at a high temperature of 1000 ° C. or higher, Before the ammonia gas reaches the workpiece 2, the ammonia gas is instantaneously decomposed in the indoor atmosphere or on the heater 5a, and the workpiece 2 cannot be appropriately nitrogenated. Therefore, in order to appropriately perform nitriding in the carburizing chamber 5, it is necessary to wait for the atmospheric temperature of the carburizing chamber 5 after the carburizing is performed and the temperature of the heater 5 a to be lowered to about 850 ° C. or less. Don't be.

  Therefore, in the heat treatment apparatus 1 according to the present invention, as described above, the carburizing treatment chamber 5 and the nitriding treatment chamber 6 are provided so as to be thermally insulated from each other. The nitriding treatment chamber 6 is configured as an independent treatment chamber having no heating device such as a heater. Therefore, the workpiece 2 after carburizing at a high temperature of 1000 ° C. or higher is taken out from the carburizing chamber 5, and then the workpiece 2 is carried into the nitriding chamber 6 to perform nitriding, thereby The work 2 can be nitrogenated using the residual heat of the work 2. Although the temperature of the workpiece 2 transferred from the carburizing chamber 5 to the nitriding chamber 6 is lowered to some extent during the transfer, the nitriding temperature is lower than the carburizing temperature as described above. The residual heat of the work 2 carried into the chamber 6 is still kept at a temperature level sufficient to perform nitriding. Since the nitriding treatment chamber 6 does not have a heater, the ammonia gas supplied from the gas injection nozzle 6a in the nitriding treatment chamber 6 is not decomposed by the heat of the heater, and after the carburizing. It is possible to reach the surface of the work 2 having residual heat. As a result, the workpiece 2 can be appropriately nitrogenated using the residual heat after carburizing.

  The cooling chamber 7 is a processing chamber for quenching and quenching the workpiece 2 after carburizing and nitriding using a refrigerant. The cooling chamber 7 is provided with a gas injection nozzle 7a for filling the chamber with a refrigerant gas such as nitrogen gas. A cooling fan 7b is provided for uniformly diffusing the refrigerant gas into the room. And this cooling chamber 7 can hold | maintain a chamber in a pressure-reduced state similarly to said heating chamber 4, the carburizing process chamber 5, and the nitriding process chamber 6, and with the opening part of said conveyance cell 3, and It is comprised so that it can connect, maintaining a pressure reduction state. Therefore, the work 2 is carried into the cooling chamber 7 from the inside of the container of the transported cell 3 that has been decompressed, and the work 2 is transported from the cooling chamber 7 to the transporting cell 3 while maintaining the decompressed state. The configuration is possible.

  A heat treatment method using the heat treatment apparatus 1 configured as described above will be described. As shown in FIG. 1, the heat treatment method according to the present invention is a heat treatment method for carbonitriding (or carbonitriding) a workpiece 2 made of steel, which is a material to be heat treated. The heat treatment method according to the present invention includes, in order, a carry-in process (process P1), a temperature rising (high frequency heating) process (process P2), a carburizing process (process P3), a nitrous (nitriding) process (process P4), and a baking process. It is carried out through each step of an input (cooling) step (process P5) and an unloading step (process P6).

  First, the work 2 is carried into the transfer cell 3 in the carry-in process (process P1). And the inside of the container of the conveyance cell 3 is vacuum-sucked, and the inside of the container of the conveyance cell 3 is decompressed. When the inside of the container is depressurized to a predetermined pressure, the depressurized state is maintained, and the depressurized state is conveyed to the heating chamber 4 of the next step (temperature raising step).

  In the temperature raising step (process P2), the opening of the transfer cell 3 that accommodates the workpiece 2 and is in a reduced pressure state is connected to the opening of the heating chamber 4 while maintaining the reduced pressure state. Subsequently, the workpiece 2 is transferred from the transfer cell 3 to the heating chamber 4. When the work 2 is transferred into the heating chamber 4, the opening of the heating chamber 4 is closed and the decompressed state in the chamber is maintained. And it supplies with electricity to the heating coil 4a of the heating chamber 4, and the workpiece | work 2 is heated up to about 1100 degreeC by high frequency heating. When the temperature of the workpiece 2 reaches about 1100 ° C., the heating chamber 4 and the transfer cell 3 are connected again, and the workpiece 2 is transferred from the heating chamber 4 to the transfer cell 3. And it is conveyed to the carburizing process chamber 5 of the next process (carburizing process) with the reduced pressure state.

  In the carburizing step (process P3), the opening of the transfer cell 3 that accommodates the workpiece 2 and is in a reduced pressure state is connected to the opening of the carburizing chamber 5 while maintaining the reduced pressure state. Subsequently, the workpiece 2 is transferred from the transfer cell 3 to the carburizing chamber 5. When the workpiece 2 is transferred into the carburizing chamber 5, the opening of the carburizing chamber 5 is closed and the decompressed state in the chamber is maintained. And the temperature of the room | chamber and the workpiece | work 2 is hold | maintained at about 1100 degreeC with the heater 5a with which the carburizing process chamber 5 was equipped. Then, a carburizing gas such as a hydrocarbon gas is supplied into the carburizing chamber 5 from the gas injection nozzle 5b, and the workpiece 2 is carburized. When a predetermined carburizing time set in advance to achieve the desired surface hardness and carburizing depth for the workpiece 2 has elapsed, the carburizing chamber 5 and the transfer cell 3 are connected again, and the workpiece 2 is carburized. It is transferred from the processing chamber 5 to the transfer cell 3. And it is conveyed to the nitriding treatment chamber 6 of the next process (nitriding process) with the reduced pressure state.

  In the nitriding step (process P4), the opening of the transfer cell 3 that accommodates the workpiece 2 and is in a reduced pressure state is connected to the opening of the nitriding treatment chamber 6 while maintaining the reduced pressure state. Subsequently, the workpiece 2 is transferred from the transfer cell 3 to the nitriding treatment chamber 6. When the workpiece 2 is transferred into the nitriding treatment chamber 6, the opening of the nitriding treatment chamber 6 is closed and the decompressed state in the chamber is maintained. Then, a nitriding gas such as ammonia gas is supplied into the nitriding treatment chamber 6 from the gas injection nozzle 6a, and the work 2 is nitrified.

  As described above, the nitriding treatment chamber 6 is not provided with a heating device such as a heater, but the workpiece 2 that has been carburized at a high temperature of about 1100 ° C. in the previous process has a lower nitriding temperature than the carburizing treatment. Therefore, the workpiece 2 can be appropriately nitrogenated using the residual heat.

  When a predetermined nitriding treatment time set in advance to achieve the desired surface hardness and nitriding depth for the workpiece 2 has elapsed, the nitriding treatment chamber 6 and the transfer cell 3 are connected again, and the workpiece 2 is transferred from the nitriding chamber 6 to the transfer cell 3. And it is conveyed to the cooling chamber 7 of the next process (quenching process) with the reduced pressure state.

  In the quenching step (process P5), the opening of the transfer cell 3 that accommodates the workpiece 2 and is in a reduced pressure state is connected to the opening of the cooling chamber 7 while maintaining the reduced pressure state. Subsequently, the workpiece 2 is transferred from the transfer cell 3 to the cooling chamber 7. When the workpiece 2 is transferred into the cooling chamber 7, the opening of the cooling chamber 7 is closed and the decompressed state in the chamber is maintained. Then, a coolant such as nitrogen gas is supplied into the cooling chamber 7 from the gas injection nozzle 7a, and the workpiece 2 is rapidly cooled. That is, the workpiece 2 after the carburizing and nitriding treatment is quenched by gas cooling. In addition to the gas cooling as described above, the quenching process performed in the cooling chamber 7 can also be performed, for example, by so-called mist cooling in which the workpiece 2 is rapidly cooled by spraying a liquid refrigerant.

  When the workpiece 2 is cooled under predetermined quenching conditions set in advance, the cooling chamber 7 and the transfer cell 3 are connected again, and the workpiece 2 is transferred from the cooling chamber 7 to the transfer cell 3. And the workpiece | work 2 is carried out from the cooling chamber 7 at the next process (unloading process) with the pressure reduction state.

  In the unloading step (process P6), the depressurized state of the transfer cell 3 containing the workpiece 2 is released and returned to the atmospheric pressure state. And the workpiece | work 2 is carried out from the conveyance cell 3, and the carburizing nitriding and hardening of the workpiece | work 2 are completed.

  FIG. 2 to FIG. 4 show various test results of the steel test pieces that have been carbonitrided by the heat treatment method using the heat treatment apparatus 1 as described above. A test piece made of chromium molybdenum steel (SCM420) was subjected to carburizing and nitriding and quenching with the heat pattern shown in FIG. That is, as described above, in order to shorten the carburizing time, carburizing is performed at a high temperature of 1100 ° C., and nitriding is performed in a temperature range of about 1100 ° C. to about 900 ° C. using the residual heat after the carburizing. Carried out. And after the nitriding, quenching by gas cooling was performed.

  The test result of the Vickers hardness test of the test piece subjected to the carburizing and nitriding treatment as described above is shown in FIG. It can be seen that the hardness is improved by the heat treatment in the range of a depth of about 0.8 mm from the surface of the test piece. That is, the effects of carburizing and nitriding and quenching are observed.

  And the test result of the fatigue test by the roller pitching test machine of the test piece which carried out the carbonitriding process as mentioned above is shown in FIG. Here, the fatigue test result of the test piece which performed only carburizing as a comparative material is written together. It can be seen that the surface fatigue strength is improved more reliably when carburizing and nitriding is performed than when only carburizing is performed.

  Thus, by performing the carburizing and nitriding treatment using the heat treatment apparatus 1 and the heat treatment method according to the present invention, the effect of improving the surface hardness of the heat-treated product and the effect of improving the fatigue strength of the heat-treated product are reliably obtained. It is understood that

  As described above, according to the heat treatment apparatus and the heat treatment method according to the present invention, the carburizing process for carburizing the work 2 and the carburizing process for nitriding the work 2 are performed separately from each other in the carburizing treatment chamber 5 and the carburizing process. It is performed separately in the nitrogen treatment chamber 6. That is, the workpiece 2 carburized in the carburizing chamber 5 is then transferred to a nitriding chamber 6 that is separate from the carburizing chamber 5, and is nitrogenated in the nitriding chamber 6. In the nitriding treatment chamber 6, nitriding is performed by utilizing the residual heat of the work 2 after carburizing without heating the work 2. Therefore, after carburizing, there is no need to wait for the temperature of the processing chamber to drop and to heat the workpiece 2 again for nitriding. Therefore, the workpiece 2 can be carburized, and then the workpiece 2 can be surely nitrogenated. At the same time, the processing time for carburizing and nitriding the workpiece 2 can be greatly shortened. As a result, the heat treatment cost when carburizing and nitriding the workpiece 2 can be significantly reduced.

  DESCRIPTION OF SYMBOLS 1 ... Heat processing apparatus, 2 ... Workpiece, 3 ... Transfer cell, 4 ... Heating chamber, 5 ... Carburizing treatment chamber, 6 ... Nitrogenation treatment chamber, 7 ... Cooling chamber.

Claims (3)

A carburizing chamber for carburizing steel workpieces and a nitrocarburizing chamber for nitriding the workpieces are separately provided, and the workpieces carburized in the carburizing chamber are transferred to the nitriding chamber and subjected to nitriding. In the heat treatment apparatus
The carburizing treatment chamber and the nitriding treatment chamber are configured to be separated from each other,
A heat treatment apparatus configured to nitrify the work by using residual heat of the work after carburizing in the carburization process room in the nitriding process room.
The nitriding treatment chamber is provided with a nitriding gas supply means for filling the nitriding treatment chamber with a nitriding gas for nitriding the workpiece,
In the nitriding treatment chamber, the nitriding gas supplied by the nitriding gas supply means is brought into contact with the workpiece having the remaining heat so as to nitrify the workpiece. The heat treatment apparatus according to claim 1.
In the heat treatment method of carburizing and nitriding steel workpieces,
A heating step for heating the workpiece to a temperature higher than the carburizing temperature capable of carburizing;
Carburizing properties for carburizing the workpiece into the workpiece heated above the carburizing temperature in the temperature raising step in a carburizing chamber equipped with a heater capable of maintaining the temperature of the workpiece above the carburizing temperature. Carburizing step of carburizing the work by contacting gas;
In a nitriding chamber separated from the carburizing chamber, a nitrous gas for nitriding the workpiece is brought into contact with the workpiece having a residual heat equal to or lower than the carburizing temperature after carburizing in the carburizing step. And a nitriding step of nitriding the workpiece.

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