Nested heat treatment process for gear hub and gear sleeve of synchronizer

Abstract

The invention provides a nested heat treatment process for a gear hub and a gear sleeve of a synchronizer. The nested heat treatment process comprises five steps of forging, isothermal normalizing, processing before heat treatment, material preparation for heat treatment and carburizing and quenching heat treatment. According to the nested heat treatment process for the gear hub and the gear sleeve of the synchronizer, on one hand, the space of the inner hole of the gear sleeve of the synchronizer is fully utilized, the installation amount is increased by embedding the gear hub of the synchronizer into the gear sleeve of the synchronizer, and the cost of a carburizing heat treatment procedure is reduced; and on the other hand, a synchronizer gear sleeve pressure quenching process is changed into a direct quenching process, so that the quenching process is simplified, the machining efficiency is improved, and a large number of machine and auxiliary materials, electric energy consumption and labor cost of the pressure quenching process are saved.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile parts processing, relates to the processing of a synchronizer gear hub and a synchronizer gear sleeve, and specifically relates to a synchronizer gear hub gear sleeve nesting heat treatment process. Background Art

[0002] Synchronizer hub and synchronizer sleeve are key components of automobile transmission. The traditional heat treatment processes of these two parts are as follows: The structure of synchronizer hub parts is similar to that of gears, and most of them are symmetrical and have small deformation during heat treatment. Therefore, a heat treatment process of direct quenching after carburizing is adopted; synchronizer sleeves have thin walls and internal spline structure characteristics, and the precision requirements of parts are generally relatively high. There are clear requirements for the roundness of the internal splines (or inner holes) of the parts, the flatness of the end faces, the perpendicularity of the end faces and the axis of the parts, and the position of important holes and slots. In order to ensure that the final size of the parts after heating meets the requirements, the heat treatment of synchronizer sleeves generally adopts a process combining carburizing cooling and secondary heating and press quenching.

[0003] Since the synchronizer gear hub adopts the heat treatment process of carburizing and then direct quenching, while the synchronizer gear sleeve adopts the process of combining carburizing cooling and secondary heating and press quenching, the heat treatment process flow of the two types of parts is also significantly different. The process flow of gear hub parts includes direct quenching after carburizing, and the process flow of gear sleeve parts includes carburizing first, then furnace cooling and secondary heating and press quenching. Since the heat treatment process flow of synchronizer gear hub and synchronizer gear sleeve is different, in actual production, the two parts need to be prepared and hot-processed separately, resulting in low processing efficiency and high processing cost. Summary of the invention

[0004] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a synchronizer gear hub and synchronizer gear sleeve nesting heat treatment process to solve the technical problems of low processing efficiency and high processing cost in the prior art process of separately heat treating the synchronizer gear hub and the synchronizer gear sleeve.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A synchronizer gear hub and gear sleeve nesting heat treatment process, the process comprising: nesting the synchronizer gear hub and the synchronizer gear sleeve together, and then performing carburizing and quenching heat treatment;

[0007] The process specifically includes the following steps:

[0008] Step 1, Forging:

[0009] The synchronizer gear hub parts raw material and the synchronizer gear sleeve parts raw material are heated and then forged. After the forging is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are obtained;

[0010] Step 2: Isothermal normalizing:

[0011] The synchronizer gear hub blank and the synchronizer gear sleeve blank are placed in the high temperature zone of the heat treatment furnace for heating; after the heating is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the high temperature zone of the heat treatment furnace, and then they are quickly cooled by upper and lower convection circulation air cooling; after the cooling is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are kept warm in the medium temperature zone of the heat treatment furnace; after the insulation is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the medium temperature zone, and then they are naturally cooled in the air;

[0012] Step 3: Processing before heat treatment:

[0013] The synchronizer gear hub blank and synchronizer gear sleeve blank after isothermal normalizing treatment are rough-machined and fine-machined by machine tools, so that the parts reach the size of the parts before heating, and the synchronizer gear hub machined parts and synchronizer gear sleeve machined parts are obtained;

[0014] Step 4: Heat treatment preparation:

[0015] After the synchronizer gear hub machine tool parts and synchronizer gear sleeve machine tool parts are nested together, they are laid flat on the parts rack and stacked layer by layer;

[0016] Step 5: Carburizing and quenching heat treatment:

[0017] Carburizing and quenching heat treatment is performed on the synchronizer gear hub machine tool processing parts and synchronizer gear sleeve machine tool processing parts which are nested together; after carburizing and quenching heat treatment, cleaning and tempering are performed to obtain synchronizer gear hub products; the synchronizer gear sleeve after cleaning and tempering is processed with a precision machine tool to obtain the synchronizer gear sleeve product.

[0018] The present invention also has the following technical features:

[0019] Specifically and preferably, in step 1, the forging temperature is 1000-1230°C.

[0020] Specifically and preferably, in step 2, the heating conditions are: heating at a temperature of 920-940° C. for 1.5-2.5 hours.

[0021] Specifically and preferably, in step 2, the cooling conditions are: the frequency of the air-cooling motor during cooling is 20 to 60 Hz, the cycle time is 100 to 400 s, and the cooling time is 3 to 9 minutes.

[0022] Specifically and preferably, in step 2, the insulation condition is: insulation at a temperature of 550-630° C. for 2.5-3.5 hours.

[0023] Specifically and preferably, in step 5, the carburizing conditions are: the strong carburizing temperature is 890-910°C, the strong carburizing potential is 0.85-1.05%, and the strong carburizing time is 3-4.5h. The quenching temperature is 800-830°C, the carbon potential before quenching is 0.80-0.90%, and the temperature equilibration time before quenching is 0.5-1.5h.

[0024] Specifically and preferably, in step five, the quenching conditions are: the quenching oil used is martensitic isothermal quenching oil, the quenching oil temperature is 100-120°C, the quenching stirring speed is 100-300 rpm, and the quenching time is 15-30 minutes.

[0025] The beneficial technical effects of the present invention compared with the prior art are as follows:

[0026] (I) The synchronizer gear hub and gear sleeve nesting heat treatment process of the present invention, on the one hand, fully utilizes the space of the inner hole of the synchronizer gear sleeve, embeds the synchronizer gear hub in the synchronizer gear sleeve to increase the loading volume, and reduces the cost of the carburizing heat treatment process; on the other hand, the synchronizer gear sleeve press quenching process is changed into a direct quenching process, which simplifies the quenching process, improves the processing efficiency, and saves a lot of machine auxiliary materials, electricity consumption and labor costs of the press quenching process.

[0027] (II) Different from the traditional serial preparation method, the present invention adopts the method of nesting the gear hub and gear sleeve parts together for flat preparation. This preparation method has the following two advantages: on the one hand, it can reduce the deformation of the roundness caused by the weight of the parts in the original serial preparation method; on the other hand, nesting the gear hub into the gear sleeve is equivalent to adding a compensation tool to the core of the gear sleeve, so that the gear hub can compensate for a certain amount of heat during quenching and cooling, which slows down the cooling speed of the parts to a certain extent, reduces the quenching deformation of the gear sleeve, and improves the processing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the synchronizer gear hub.

[0029] Figure 2 It is a schematic diagram of the structure of the synchronizer gear sleeve.

[0030] Figure 3 It is a schematic diagram of the nested structure of the synchronizer gear hub and the synchronizer gear sleeve.

[0031] Figure 4 This is a metallographic photograph of the ideal normalizing structure of the synchronizer gear sleeve of the present invention.

[0032] Figure 5 This is a metallographic photo of the most serious banded structure in the normalizing structure of the synchronizer gear sleeve blank suitable for the nesting process

[0033] Figure 6The traditional preparation method of synchronizer gear sleeve is demonstrated.

[0034] Figure 7 Demonstrates the traditional method of preparing synchronizer hubs.

[0035] Figure 8 The method for preparing the synchronizer gear sleeve and synchronizer gear hub of the present invention is demonstrated.

[0036] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0037] It should be noted that all parts, equipment and materials used in the present invention, unless otherwise specified, are conventional parts, equipment and materials known in the art. For example, the martensitic isothermal quenching oil used for quenching is Houghto Mar-Temp 355 isothermal quenching oil known in the prior art.

[0038] In accordance with the above technical scheme, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0039] The technical ideas of the present invention are as follows:

[0040] Since the heat treatment technology requirements of the synchronizer gear hub and the synchronizer gear sleeve are the same and the materials are similar or the same, they cannot be heat treated in the same furnace only due to different process methods. Figure 3 ) is a new process that uses the same furnace for production, that is, the parts that originally needed to be produced separately are combined into one furnace for production. The core of this production process needs to solve two technical difficulties: one is whether the nested preparation of the gear hub and gear sleeve will cause the local gap of the parts to be small, which will affect the carburizing effect of the parts. The other is whether the deformation of the gear sleeve after heating meets the requirements after changing the gear sleeve from press quenching to direct quenching.

[0041] In view of the above technical difficulties, the present invention studies the influence of factors such as different pre-heat structures, heat treatment equipment with different furnace temperature uniformity, different heat treatment process parameters, and different heat treatment preparation methods on the final result of the nested heat treatment process (including whether the heat treatment indicators of parts and the key dimensions of parts meet the requirements of the design drawings), and identifies the boundary conditions of each influencing factor through a large number of experiments. After verification, the boundary conditions suitable for the nested heat treatment production of the hub and sleeve are summarized, as shown in Example 1 for details.

[0042] Embodiment 1:

[0043] This embodiment provides a synchronizer gear hub sleeve nesting heat treatment process, which specifically includes the following steps:

[0044] Step 1, Forging:

[0045] The synchronizer gear hub parts raw materials and synchronizer gear sleeve parts raw materials are heated to 1000-1230° C. and then subjected to a forging process. After the forging is completed, a synchronizer gear hub blank and a synchronizer gear sleeve blank are obtained.

[0046] In this embodiment, the raw materials for the synchronizer gear hub parts and the synchronizer gear sleeve parts are made of low-carbon alloy steel with limited hardenability bandwidth (for example, 8620RH alloy steel, 20CrMnTiH alloy steel, etc. are preferred). Their various technical indicators should at least meet the national standards and relevant industry standards, and the maximum fluctuation of the end hardenability value of the material cannot exceed 6HRC.

[0047] Step 2: Isothermal normalizing:

[0048] The synchronizer gear hub blank and the synchronizer gear sleeve blank are placed in a heat treatment furnace and heated at a temperature of 930±10℃ for 2±0.5h; after the heating is completed, after the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the high temperature zone of the heat treatment furnace, they are quickly cooled by up and down convection circulation air cooling. During cooling, the air cooling motor frequency is 20-60Hz, the cycle time is 100-400s, and the cooling time is 6±3 minutes; after the cooling is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are kept in the medium temperature zone of the heat treatment furnace at 590±40℃ for 3±0.5h, and finally, after the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the medium temperature zone, they are naturally cooled in the air.

[0049] In this embodiment, the heat treatment furnace (including an isothermal normalizing furnace and a carburizing and quenching furnace) adopts a heat treatment furnace known in the prior art, and its furnace temperature uniformity must comply with the "Requirements for Heat Treatment Processes in the Automotive Industry" (CQI-9 Standard) issued by the Automotive Industry Action Group (AIAG). Generally, the deviation of the nine-point temperature measurement results must be less than ±10°C.

[0050] In this embodiment, the surface hardness of the blank should be in the range of 153HB to 185HB, and the normal structure of the blank should be uniformly distributed ferrite and lamellar pearlite; when there is abnormal structure, the amount of bainite, acicular ferrite and broken pearlite (Widmanstätten structure, acicular ferrite + bainite) should not exceed 30% of the pearlite content. Acicular ferrite, martensite is not allowed to exist, and the banded structure level is less than or equal to level 2 (such as Figure 5 The normalized structure of the blank obtained after the isothermal normalizing process of this embodiment is as follows: Figure 4 As shown, from Figure 4It can be seen that the normalized structure has no banding trend and is a uniform pearlite plus ferrite isothermal normalized structure, which meets the above requirements for the blank structure and is a more ideal normalized structure.

[0051] Step 3: Processing before heat treatment:

[0052] The synchronizer gear hub blank and synchronizer gear sleeve blank after isothermal normalizing treatment are rough-machined and fine-machined by machine tools, so that the parts reach the part size before heating, and the synchronizer gear hub machined parts and synchronizer gear sleeve machined parts are obtained.

[0053] Step 4: Heat treatment preparation:

[0054] Nest the synchronizer gear hub machine tool parts and synchronizer gear sleeve machine tool parts together and lay them flat on the parts rack. When one layer is full, prepare the next layer (such as Figure 8 shown).

[0055] In this embodiment, it has been verified that in order to achieve a better effect of controlling deformation, the gear hub embedded in the gear sleeve must be the corresponding accessory gear hub in the designed synchronizer assembly, rather than other gear hubs whose outer diameter is smaller than the inner diameter of the gear sleeve. In addition, since the larger the thin-walled gear sleeve parts are, the more difficult it is to control the heat treatment deformation, after repeated tests, it was determined that only parts with a spline minor diameter of less than 160mm in the gear sleeve can use the gear hub and gear sleeve nesting process.

[0056] Step 5: Carburizing and quenching heat treatment:

[0057] The synchronizer gear hub machine tool parts and synchronizer gear sleeve machine tool parts that are nested together are subjected to carburizing and quenching heat treatment, with the strong carburizing temperature of 890-910°C, the strong carburizing potential of 0.85-1.05%, and the strong carburizing time of 3-4.5h. The quenching temperature is 800-830°C, the carbon potential before quenching is 0.80-0.90%, and the temperature averaging time before quenching is 0.5-1.5h. The quenching uses martensitic isothermal graded quenching oil, the quenching oil temperature is 110±10°C, the quenching stirring speed is 200±100 rpm throughout the process, and the quenching time is 15-30 minutes; after the carburizing and quenching heat treatment, it is cleaned and tempered to obtain the synchronizer gear hub product (the synchronizer gear hub has no finishing process after heating); the synchronizer gear sleeve after cleaning and tempering is processed with a precision machine tool to obtain the synchronizer gear sleeve product.

[0058] In this implementation, since the quality of carburizing and quenching uniformity has an important influence on the consistency of heat treatment indicators and part deformation after nested heat treatment, the synchronizer gear hub sleeve heat treatment process has high requirements for the uniformity of carburizing and quenching in the heat treatment furnace. Therefore, in order to select suitable heat treatment equipment, the following method is used to verify whether different heat treatment equipment can meet the requirements of carburizing and quenching uniformity: Cut a gear part with good pre-heating uniformity into nine pieces of uniform size, and refer to the nine-point temperature measurement method to place the nine test blocks at the center and eight corners of the material preparation area geometry (the material preparation area geometry is mostly a rectangular shape) for carburizing and quenching. Generally, the carburizing hardening layer depth of 1.0±0.2mm is used for testing. If the maximum deviation of the hardening layer depth at each point and the average value of the hardening layer depth at nine points is less than 0.05mm, it means that the equipment can meet the requirements of the nested process for carburizing and quenching uniformity. The test results of carburizing and quenching uniformity are shown in Table 1:

[0059] Table 1. Test results of nine-point carburizing and quenching uniformity of different multi-purpose furnaces (Note: the values ​​in Table 1 are the depth of the hardened layer of the test block after carburizing and quenching)

[0060] Test block number Multipurpose furnace 2# Multipurpose furnace 3# Multipurpose furnace 6# Multipurpose furnace 10# Multipurpose furnace 12# 1 0.75mm 0.74mm 0.85mm 0.78mm 0.75mm 2 0.75mm 0.74mm 0.84mm 0.87mm 0.82mm 3 0.75mm 0.77mm 0.85mm 0.79mm 0.80mm 4 0.78mm 0.76mm 0.85mm 0.91mm 0.76mm 5 0.74mm 0.75mm 0.84mm 0.8mm 0.79mm 6 0.77mm 0.74mm 0.84mm 0.82mm 0.79mm 7 0.73mm 0.76mm 0.84mm 0.94mm 0.80mm 8 0.76mm 0.78mm 0.85mm 0.81mm 0.85mm 9 0.79mm 0.8mm 0.86mm 0.85mm 0.83mm Deviation value 0.033mm 0.04mm 0.014mm 0.101mm 0.051mm

[0061] It can be seen from Table 1 that multi-purpose furnaces 2#, 3# and 6# can meet the requirements of the nested process for carburizing and quenching uniformity, while multi-purpose furnaces 10# and 12# cannot meet the requirements of the nested process for carburizing and quenching uniformity.

[0062] Effect verification of Example 1:

[0063] (A) Key dimension inspection of synchronizer hub and synchronizer sleeve products

[0064] The key dimensions of the synchronizer gear hub product and synchronizer gear sleeve product obtained by adopting the synchronizer gear hub gear sleeve nesting heat treatment process of the present invention are shown in Table 2:

[0065] Table 2. Key dimensions of typical synchronizer gear hub and synchronizer gear sleeve products after nesting heat treatment

[0066]

[0067] As can be seen from Table 2, the test results show that the key dimensions of the synchronizer gear hub product and the synchronizer gear sleeve product obtained by the present invention meet the technical index requirements, and the key dimensions are no different from those of the traditional heat treatment.

[0068] (B) Carburization uniformity test of adjacent spline teeth of synchronizer hub products and synchronizer sleeve products

[0069] In order to detect the carburizing uniformity of the mutually adjacent spline teeth of the synchronizer gear hub product and the synchronizer gear sleeve product obtained by the synchronizer gear hub gear sleeve nesting heat treatment process of the present invention, three teeth are randomly selected every 120 degrees on the circumference of the synchronizer gear hub product and the synchronizer gear sleeve product, respectively marked as A, B, and C, and then their carburizing layer depth, metallographic structure and other heat treatment technical indicators are respectively detected. The test results are shown in Table 3:

[0070] Table 3. Typical synchronizer gear hub sleeve product nesting heat treatment process post-heat treatment indicators

[0071]

[0072] As can be seen from Table 3, the test results show that the carburizing uniformity of the synchronizer gear hub product and the synchronizer gear sleeve product obtained by the present invention meets the technical index requirements, and the carburizing uniformity is no different from that of the traditional heat treatment.

[0073] Comparative Example 1:

[0074] This comparative example provides a synchronizer gear hub sleeve heat treatment process, which is basically the same as that of Example 1, except that step four and step five are different.

[0075] In this comparative example, step 4 is specifically as follows: placing the synchronizer gear hub machine tool processing parts and the synchronizer gear sleeve machine tool processing parts on the parts rack respectively, such as Figure 6 (gear sleeves in series) and Figure 7 (gear hubs placed in series) as shown.

[0076] In this comparative example, step five specifically includes: performing carburizing and quenching heat treatment on the synchronizer gear hub machine tool processing part and the synchronizer gear sleeve machine tool processing part respectively, and the conditions of the carburizing and quenching heat treatment are exactly the same as those of step five of embodiment 1.

[0077] Comparison of the effects of Comparative Example 1 and Example 1:

[0078] Table 4. Comparison of key dimensions of the same gear hub products after nesting heat treatment in different preparation methods

[0079]

[0080]

[0081] From the data in Table 4, it can be seen that the dimensional accuracy of the parts prepared horizontally (numbered 1, 2, and 3 in Table 4) after heating is significantly better than that of the parts prepared in series (numbered 1#, 2#, and 3# in Table 4).

[0082] Comparative Example 2:

[0083] This comparative example provides a normalizing heat treatment process for a synchronizer gear hub sleeve blank, which is substantially the same as that of Example 1, except that step two is different.

[0084] In this comparative example, step two is specifically as follows: placing the synchronizer gear hub blank and the synchronizer gear sleeve blank into a heat treatment furnace and heating them at a temperature of 930±10°C for 3±1h; after the heating is completed, after the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the heat treatment furnace, they are cooled naturally in the air (i.e., the cooling speed is not artificially controlled).

[0085] Comparison of the effects of Comparative Example 2 and Example 1:

[0086] Table 5. Comparison of key dimensions of the same gear sleeve products with different blank structures after nesting heat treatment

[0087]

[0088] From the data in Table 5, it can be seen that the dimensional accuracy of the gear sleeve parts (numbered 1, 2, and 3 in Table 5) produced by isothermal normalizing after heating is significantly better than that of the gear sleeve parts (numbered 1#, 2#, and 3# in Table 5) produced by ordinary normalizing.

Claims

1. A synchronizer gear hub sleeve nesting heat treatment process, characterized in that: The process includes: after the synchronizer gear hub and the synchronizer gear sleeve are nested together, carburizing and quenching heat treatment is performed; The process specifically includes the following steps: Step 1, Forging: The synchronizer gear hub parts raw material and the synchronizer gear sleeve parts raw material are heated and then forged. After the forging is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are obtained; Step 2: Isothermal normalizing: The synchronizer gear hub blank and the synchronizer gear sleeve blank are placed in the high temperature zone of the heat treatment furnace for heating; after the heating is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the high temperature zone of the heat treatment furnace, and then they are quickly cooled by upper and lower convection circulation air cooling; after the cooling is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are kept warm in the medium temperature zone of the heat treatment furnace; after the insulation is completed, the synchronizer gear hub blank and the synchronizer gear sleeve blank are taken out of the medium temperature zone, and then they are naturally cooled in the air; Step 3: Processing before heat treatment: The synchronizer gear hub blank and synchronizer gear sleeve blank after isothermal normalizing treatment are rough-machined and fine-machined by machine tools, so that the parts reach the size of the parts before heating, and the synchronizer gear hub machined parts and synchronizer gear sleeve machined parts are obtained; Step 4: Heat treatment preparation: After the synchronizer gear hub machine tool parts and synchronizer gear sleeve machine tool parts are nested together, they are laid flat on the parts rack and stacked layer by layer; Step 5: Carburizing and quenching heat treatment: Carburizing and quenching heat treatment is performed on the synchronizer gear hub machine tool processing parts and synchronizer gear sleeve machine tool processing parts which are nested together; after carburizing and quenching heat treatment, cleaning and tempering are performed to obtain synchronizer gear hub products; the synchronizer gear sleeve after cleaning and tempering is processed with a precision machine tool to obtain the synchronizer gear sleeve product.

2. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step 1, the forging temperature is 1000-1230°C.

3. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step 2, the heating condition is: heating at a temperature of 920-940° C. for 1.5-2.5 hours.

4. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step 2, the cooling conditions are as follows: the frequency of the air-cooling motor during cooling is 20 to 60 Hz, the cycle time is 100 to 400 seconds, and the cooling time is 3 to 9 minutes.

5. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step 2, the insulation condition is: insulation at a temperature of 550-630° C. for 2.5-3.5 hours.

6. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step 5, the carburizing conditions are as follows: the carburizing temperature is 890-910°C, the carburizing potential is 0.85-1.05%, the carburizing time is 3-4.5h, the quenching temperature is 800-830°C, the carbon potential before quenching is 0.80-0.90%, and the temperature equilibration time before quenching is 0.5-1.5h.

7. The synchronizer gear hub sleeve nesting heat treatment process according to claim 1, characterized in that: In step five, the quenching conditions are as follows: the quenching oil used is martensitic isothermal quenching oil, the quenching oil temperature is 100-120° C., the quenching stirring speed is 100-300 rpm, and the quenching time is 15-30 minutes.

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