Induction vacuum carburizing heat treatment process and device

Abstract

The application provides an inductive vacuum carburizing heat treatment process and device, and the inductive vacuum carburizing heat treatment process comprises the following steps: S10, inductive heating is performed on a workpiece, and the workpiece is heated to a quenching temperature, and the inductive heating is performed under mixed gas; S20, the workpiece obtained in S10 is subjected to cooling treatment; S30, the workpiece obtained in S20 is subjected to cryogenic treatment; the inductive heating comprises the following steps: S11, vacuumizing, mixed gas is introduced, and heating is performed through an induction power supply; S12, the S11 is repeatedly operated multiple times; the mixed gas is composed of acetylene and nitrogen, and the ratio of the acetylene and the nitrogen is 2:3. The application solves the technical problem that the existing continuous inductive heat treatment process is prone to reducing the hardness and wear resistance of the workpiece, and through changing the surface treatment layer structure of the workpiece, the technical effect of improving the hardness and wear resistance of the workpiece is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal carburizing, in particular to an induction vacuum carburizing heat treatment process and device. BACKGROUND

[0002] Currently, in the continuous induction heat treatment process, the metal workpiece is oxidized and decarburized, thereby forming an oxide skin on the surface of the workpiece, and simultaneously affecting the carburizing effect, resulting in reduced hardness and wear resistance of the workpiece. SUMMARY

[0003] The present application solves the technical problem that the existing continuous induction heat treatment process easily leads to reduced hardness and wear resistance of the workpiece, and achieves the technical effect of improving the hardness and wear resistance of the workpiece by changing the structure of the surface treatment layer of the workpiece.

[0004] To solve the above problems, the present application provides an induction vacuum carburizing heat treatment process, comprising the following steps: S10: induction heating of the workpiece, and heating to quenching temperature, and the induction heating is carried out under mixed gas; S20: cooling treatment of the workpiece obtained in S10; S30: cryogenic treatment of the workpiece obtained in S20; the induction heating comprises the following steps: S11: vacuumizing, introducing mixed gas, and heating by induction power supply; S12: repeatedly operating S11 multiple times; the mixed gas is composed of acetylene and nitrogen, and the ratio of acetylene to nitrogen is 2:3.

[0005] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: specifically, the graphite applied on the surface of the workpiece can effectively prevent the workpiece from decarburization in the induction heating process. Induction heating surface quenching is a quenching method that uses electromagnetic induction principle to generate high-density induced current on the surface layer of the workpiece, rapidly heats the workpiece to austenite state, and then rapidly cools to obtain martensite structure. When an alternating current with a certain frequency passes through the induction coil, an alternating magnetic field with the same frequency as the current changes is generated inside and outside the induction coil. When the metal workpiece is placed in the induction coil, an induced current with the same frequency as the induction coil and opposite direction is generated in the workpiece under the action of the magnetic field. Since the induced current forms a closed loop along the surface of the workpiece, it is usually called eddy current. The eddy current converts electrical energy into heat energy and rapidly heats the surface of the workpiece. The eddy current is mainly distributed on the surface of the workpiece, and almost no current passes through the inside of the workpiece, so that the surface of the workpiece is rapidly heated to quenching temperature by means of current heat effect. When the surface of the workpiece is heated to a certain temperature in the induction coil, the workpiece is rapidly cooled to obtain martensite structure on the surface layer. Then, cryogenic treatment is performed, which can improve the production efficiency, reduce residual austenite, stabilize the size of the workpiece and reduce the internal stress of the workpiece. The above process can change the structure of the metal surface treatment layer, so that the surface layer of the low-carbon steel workpiece has the processing method of the surface layer of the high-carbon steel workpiece, and the surface layer of the workpiece has high hardness and wear resistance, while the center part of the workpiece still maintains the toughness and plasticity of the low-carbon steel. Moreover, the process steps are simple and have high operability, and are easy to implement.

[0006] The circulation pulse vacuumization and the filling of mixed gas in the induction heating process can effectively solve the problem of oxidation and decarburization of the workpiece in the atmosphere, and can enable the workpiece to be carburized in a vacuum low-pressure environment.

[0007] Compared with the induction heating quenching in the ordinary atmospheric environment, in the present application, nitrogen is used as the protective gas in the induction heating process, and acetylene gas with a certain concentration is used to increase carbon, and the ratio of acetylene and nitrogen is particularly limited, so that carburization can be carried out and the surface of the workpiece can be prevented from being oxidized.

[0008] In one example of the present application, the cooling treatment is spraying quenching liquid on the surface of the workpiece obtained in S10.

[0009] Compared with the prior art, the technical effects achieved by the technical scheme are as follows: the quenching liquid is used to ensure that the austenite can be cooled at a speed exceeding the critical cooling speed, so as to obtain martensite structure. The quenching liquid sprayed on the surface of the workpiece can rapidly cool the workpiece, and the quenching liquid can be replaced according to different heat treatment processes.

[0010] In one example of the present application, the cryogenic treatment is carried out in a liquid nitrogen tank.

[0011] Compared with the prior art, the technical effects reached by adopting the technical scheme are as follows: the liquid nitrogen cabin is used for the cryogenic process, the cryogenic process can reduce residual austenite, stabilize the size of the workpiece, and reduce the residual pressure in the workpiece; in addition, the liquid nitrogen cabin can provide nitrogen for the induction heating process of the workpiece, so that the induction heating is carried out in a protective atmosphere to prevent the workpiece from being oxidized.

[0012] The application further provides an induction vacuum carburizing heat treatment device for realizing the induction vacuum carburizing heat treatment process of any one of the examples, and the carburizing heat treatment device comprises: a workbench for placing the workpiece; an induction heating chamber for induction heating the workpiece; a spraying device for cooling the workpiece; and a liquid nitrogen cabin for cryogenic treatment of the workpiece.

[0013] Compared with the prior art, the technical effects reached by adopting the technical scheme are as follows: the workpiece is first passed through the induction heating chamber, then passed through the spraying device, and finally passed through the liquid nitrogen cabin; the induction vacuum carburizing heat treatment device provided by the application has all the beneficial effects of the induction vacuum carburizing heat treatment process of any one of the examples, and details are not repeated here.

[0014] In one example of the application, the outlet end of the induction heating chamber is provided with a conveying device, and the conveying device is used for sequentially conveying the workpiece to the spraying device and the liquid nitrogen cabin.

[0015] Compared with the prior art, the technical effects reached by adopting the technical scheme are as follows: after the workpiece passes through the induction heating chamber, the workpiece falls on the conveying device, and the workpiece is rapidly cooled by water sprayed by the spraying device; then the workpiece is conveyed to the liquid nitrogen cabin by the conveying device for cryogenic treatment; after the treatment is completed, the workpiece is sent out of the liquid nitrogen cabin, and the treatment of the workpiece is completed; through the conveying device, the operation is simple and fast, time and labor can be saved, and work efficiency is improved.

[0016] In one example of the application, the induction heating chamber is externally wound with an induction coil, and the induction coil is controlled by an induction power supply.

[0017] Compared with the prior art, the technical effects reached by adopting the technical scheme are as follows: according to the size of the heat-treated workpiece, the speed of the workpiece movement and other factors, the current size of the induction power supply is adjusted, and the workpiece surface can be rapidly heated to quenching temperature by relying on the current heat effect.

[0018] In one example of the application, the induction heating chamber is provided with a pipeline one, a pipeline three and a pipeline four, the liquid nitrogen cabin is provided with a pipeline two, the pipeline one is communicated with the pipeline two; a valve one is installed on the pipeline one, a valve three is installed on the pipeline three, a valve four is installed on the pipeline four, and a valve two is installed on the pipeline two; in the case that the valve one is opened, the valve two is closed; in the case that the valve three is opened, the valve one and the valve four are closed.

[0019] Compared with the prior art, the technical effects reached by adopting the technical scheme are that the mixed gas flows between the pipes to realize the gas delivery, and the valve can control the gas pressure and flow of nitrogen and acetylene, so that the efficiency of the induction heating is higher.

[0020] In an example of the present application, the induction vacuum carburizing heat treatment device further comprises a control device for controlling the opening or closing of the valve one, the valve two, the valve three and the valve four.

[0021] Compared with the prior art, the technical effects reached by adopting the technical scheme are that the control device is used to control the opening or closing of the valve, which is convenient and fast and greatly saves manpower. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application provides an induction vacuum carburizing heat treatment process flow diagram.

[0023] Figure 2 It is an acetylene concentration-time change graph.

[0024] Figure 3 The present application provides an induction vacuum carburizing heat treatment device structure diagram.

[0025] BRIEF DESCRIPTION OF DRAWINGS

[0026] 10-Workbench; 11-Workpiece; 20-Vacuum pump; 30-Induction heating chamber; 31-Induction coil; 32-Induction power supply; 33-Pipe one; 33a-Valve one; 34-Pipe three; 34a-Valve three; 35-Pipe four; 35a-Valve four; 40-Spraying device; 50-Liquid nitrogen tank; 51-Pipe two; 51a-Valve two; 60-Conveying device; 70-Control device; 80-Filter; 90-Acetylene bottle. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below.

[0028] Example one:

[0029] Referring to Figure 1 The present embodiment provides an induction vacuum carburizing heat treatment process, comprising the following steps:

[0030] S10: Induction heating is performed on the workpiece, and the workpiece is heated to quenching temperature, and the induction heating is performed under mixed gas;

[0031] S20: The workpiece obtained in S10 is subjected to cooling treatment;

[0032] S30: The workpiece obtained in S20 is subjected to cryogenic treatment;

[0033] The induction heating comprises the following steps:

[0034] S11: vacuumizing, filling mixed gas, and heating by induction power supply;

[0035] S12: repeatedly operating S11 for multiple times;

[0036] The mixed gas is composed of acetylene and nitrogen, and the ratio of acetylene to nitrogen is 2:3.

[0037] Specifically, smearing graphite on the surface of the workpiece can effectively prevent decarburization of the workpiece during induction heating. Induction heating surface quenching is a quenching method that utilizes electromagnetic induction principle to generate high-density induced current on the surface layer of the workpiece, rapidly heats the workpiece to austenite state, and then rapidly cools to obtain martensite structure. When an alternating current of a certain frequency passes through the induction coil, an alternating magnetic field with the same frequency as the current changes will be generated inside and outside the induction coil. When the metal workpiece is placed in the induction coil, an induced current with the same frequency as the induction coil and opposite direction will be generated in the workpiece under the action of the magnetic field. Since the induced current forms a closed loop along the surface of the workpiece, it is usually called eddy current. The eddy current converts electrical energy into heat energy, rapidly heating the surface of the workpiece. The eddy current is mainly distributed on the surface of the workpiece, and almost no current passes through the inside of the workpiece, relying on the current heat effect to rapidly heat the surface of the workpiece to quenching temperature. When the surface of the workpiece is heated to a certain temperature in the induction coil, immediate cooling treatment is performed to rapidly cool the workpiece, so that the surface layer obtains martensite structure. Then, cryogenic treatment is performed, which can improve production efficiency, reduce residual austenite, stabilize the size of the workpiece, and reduce the internal stress of the workpiece. The above process can change the structure of the metal surface treatment layer, so that the surface layer of the low-carbon steel workpiece has the processing method of the surface layer of the high-carbon steel workpiece, so that the surface layer of the workpiece has high hardness and wear resistance, while the center part of the workpiece still maintains the toughness and plasticity of the low-carbon steel. Moreover, the above process steps are simple and have high operability, and are easy to implement.

[0038] Specifically, cyclic pulse vacuumizing and filling mixed gas can effectively solve the problem of oxidation and decarburization of the workpiece in the atmosphere, and can also enable the workpiece to be carburized in a vacuum low-pressure environment.

[0039] Figure 2 Specifically, compared with induction heating quenching in a common atmospheric environment, in the present application, nitrogen is used as protective gas during induction heating, and acetylene gas with a certain concentration is used for carburization, and the ratio of acetylene to nitrogen is also specifically limited, so that carburization can be achieved and the surface of the workpiece can be prevented from being oxidized. The inside of the induction heating chamber is first vacuumized, then filled with acetylene+nitrogen mixed gas, then vacuumized again, then filled with acetylene+nitrogen mixed gas again, and the process of cyclic pulse vacuumizing and filling acetylene+nitrogen mixed gas is repeated, so as to achieve the effect of carburization. Figure 2 is a graph of the change of acetylene concentration with time.​

[0040] Further, the cooling treatment is to spray quenching liquid on the surface of the workpiece obtained in S10.

[0041] Specifically, the quenching liquid is used to ensure that the austenite can be cooled at a speed exceeding the critical cooling speed, so as to obtain the martensite structure. The quenching liquid is sprayed on the surface of the workpiece, which can rapidly cool the workpiece. The quenching liquid can be replaced according to different heat treatment processes. For example, the quenching liquid can be water.

[0042] Further, the cryogenic treatment is performed in a liquid nitrogen tank.

[0043] Specifically, the liquid nitrogen tank is used to perform the cryogenic process. The cryogenic treatment can reduce residual austenite, stabilize the size of the workpiece, and reduce the internal residual pressure of the workpiece. In addition, the liquid nitrogen tank can also provide nitrogen for the induction heating process of the workpiece, so that the induction heating is performed in a protective atmosphere to prevent the workpiece from being oxidized.

[0044] Specifically, the cryogenic process can precipitate ultra-fine carbides, improve the wear resistance of the workpiece, refine the grains, improve the impact toughness of the workpiece, transform the residual austenite, improve the hardness and wear resistance of the workpiece, stabilize the size of the workpiece, improve the corrosion resistance of the martensitic stainless steel by several times, improve the polishing performance of the workpiece, improve the electrical conductivity and corrosion resistance of non-ferrous metals, and greatly reduce the internal thermal stress and mechanical stress of the material after the cryogenic treatment. In the cooling process, plastic flow occurs in the micropore or stress concentration site, and in the heating process, compressive stress occurs on the surface of these sites, which can greatly reduce the damage of defects to the local performance of the workpiece, thereby effectively reducing the possibility of deformation and cracking of the metal workpiece, and improving the size accuracy of the workpiece.

[0045] Embodiment Two:

[0046] Referring to Figure 3 The embodiment provides a carburizing heat treatment device for realizing the carburizing heat treatment process of any one of the above examples. The carburizing heat treatment device comprises: a workbench 10 for placing a workpiece 11; an induction heating chamber 30 for performing induction heating on the workpiece 11; a spraying device 40 for performing cooling treatment on the workpiece 11; and a liquid nitrogen tank 50 for performing cryogenic treatment on the workpiece 11.

[0047] Specifically, the workpiece 11 is fixed on the workbench 10, and a conveying belt is arranged on the workbench 10. The workpiece 11 is sent to the induction heating chamber 30 to perform induction heating surface quenching treatment. After the workpiece 11 uniformly passes through the induction heating chamber 30, the workpiece 11 is conveyed to the spraying device 40. The spraying device 40 sprays quenching liquid on the surface of the workpiece 11 to rapidly cool the workpiece 11. Then, the workpiece 11 is conveyed to the liquid nitrogen tank 50 to perform cryogenic process. After completion, the workpiece 11 is sent out of the liquid nitrogen tank 50.

[0048] Further, the outlet end of the induction heating chamber 30 is provided with a conveying device 60, which is used to sequentially convey the workpiece 11 to the spraying device 40 and the liquid nitrogen cabin 50.

[0049] Specifically, the conveying device 60 is a conveying chain, and the workpiece 11 falls on the conveying chain after passing through the induction heating chamber 30, and the workpiece 11 is rapidly cooled by the water sprayed by the spraying device. Then the workpiece 11 is conveyed by the conveying device 60 to the liquid nitrogen cabin 50 for cryogenic treatment, and after the treatment is completed, the workpiece is sent out of the liquid nitrogen cabin 50, and the treatment of the workpiece is completed. Through the conveying device 60, the operation is simple and fast, which can save time and effort and improve work efficiency.

[0050] Further, the induction heating chamber 30 is externally wound with an induction coil 31, and the induction coil 31 is controlled by an induction power supply 32.

[0051] Specifically, according to the size of the heat-treated workpiece 11, the speed of the workpiece 11, and other factors, the current of the induction power supply is adjusted, and the surface of the workpiece 11 can be rapidly heated to quenching temperature by relying on the current heat effect.

[0052] Further, the induction heating chamber 30 is provided with a pipe one 33, a pipe three 34 and a pipe four 35, and the liquid nitrogen cabin 50 is provided with a pipe two 51, and the pipe one 33 communicates with the pipe two 51; the pipe one 33 is provided with a valve one 33a, the pipe three 34 is provided with a valve three 34a, the pipe four 35 is provided with a valve four 35a, and the pipe two 51 is provided with a valve two 51a; in the case that the valve one 33a is opened, the valve two 51a is closed; in the case that the valve three 34a is opened, the valve one 33a and the valve four 35a are closed.

[0053] Specifically, the valve two 51a is always open, and only in the case that the valve one 33a is opened, the valve two 51a is closed. In the case that the valve three 34a is closed, the valve one 33a and the valve four 35a are opened.

[0054] Specifically, the pipe three 34 communicates with the vacuum pump 20, and then the vacuum pump 20 can pump the induction heating chamber to be vacuumized.

[0055] Specifically, the filter 80 communicates with the pipe one 33 and the pipe two 51, the liquid nitrogen volatilized in the liquid nitrogen cabin 50 flows in the pipe two 51, and after passing through the filter 80, the valve one 33a is opened, and then pure nitrogen gas is filled into the induction heating chamber 30.

[0056] Specifically, the pipe four 35 communicates with the acetylene bottle 90, and after the valve four 35a is opened, acetylene is filled into the induction heating chamber 30. By controlling the valves, the proportion of acetylene and nitrogen gas filled into the induction heating chamber 30 can be controlled, and the proportion of acetylene and nitrogen gas is 2:3.

[0057] Further, the inductive vacuum carburizing heat treatment device further comprises a control device 70, which controls the opening or closing of the valve one 33a, the valve two 51a, the valve three 34a and the valve four 35a respectively.

[0058] Specifically, the opening or closing of the valves is controlled by the control device 70, which is convenient and fast, and greatly saves manpower.

[0059] Although the present application is disclosed as above, it is not limited thereto. Any person skilled in the art, without departing from the spirit and scope of the present application, can make various changes and modifications, therefore the protection scope of the present application should be subject to the range defined by the claims.

Claims

1. An induction vacuum carburizing heat treatment process, characterized in that, The method comprises the following steps: S10: applying graphite on the surface of the workpiece, then performing induction heating on the workpiece and heating to quenching temperature, and the induction heating is performed under mixed gas; S20: performing cooling treatment on the workpiece obtained in S10; S30: performing cryogenic treatment on the workpiece obtained in S20; The induction heating comprises the following steps: S11: vacuumizing, introducing mixed gas, and heating by induction power supply; S12: repeatedly operating S11 for multiple times; The mixed gas is composed of acetylene and nitrogen, and the ratio of the acetylene to the nitrogen is 2:3; The cooling treatment is spraying quenching liquid on the surface of the workpiece obtained in S10; The cryogenic treatment is performed in a liquid nitrogen tank.

2. An inductive vacuum carburizing heat treatment apparatus for carrying out the carburizing heat treatment process according to claim 1, characterized in that, The carburizing heat treatment device comprises: a workbench (10) for placing the workpiece; an induction heating chamber (30) for performing induction heating on the workpiece; a spraying device (40) for performing cooling treatment on the workpiece; a liquid nitrogen tank (50) for performing cryogenic treatment on the workpiece; The induction heating chamber (30) is provided with a pipeline one (33), a pipeline three (34) and a pipeline four (35), and the liquid nitrogen tank (50) is provided with a pipeline two (51), and the pipeline one (33) communicates with the pipeline two (51); The pipeline one (33) is provided with a valve one (33a), the pipeline three (34) is provided with a valve three (34a), the pipeline four (35) is provided with a valve four (35a), and the pipeline two (51) is provided with a valve two (51a); When the valve one (33a) is opened, the valve two (51a) is closed; When the valve three (34a) is opened, the valve one (33a) and the valve four (35a) are closed; A filter (80) communicates with the pipeline one (33) and the pipeline two (51), the evaporated liquid nitrogen in the liquid nitrogen tank (50) flows in the pipeline two (51), and after passing through the filter (80), when the valve one (33a) is opened, pure nitrogen gas is filled into the induction heating chamber (30); The pipeline four (35) communicates with an acetylene bottle (90), and when the valve four (35a) is opened, acetylene is filled into the induction heating chamber (30).

3. The induction vacuum carburizing heat treatment apparatus according to claim 2, characterized in that, An conveying device (60) is arranged at the outlet end of the induction heating chamber (30), and the conveying device (60) is used for sequentially conveying the workpiece to the spraying device (40) and the liquid nitrogen tank (50).

4. The induction vacuum carburizing heat treatment apparatus according to claim 2, wherein An induction coil (31) is wound outside the induction heating chamber (30), and the induction coil (31) is controlled by an induction power supply (32).

5. The apparatus of claim 2 wherein, The induction vacuum carburizing heat treatment device further comprises a control device (70) for controlling the opening or closing of the valve one (33a), the valve two (51a), the valve three (34a) and the valve four (35a).

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