Online heat treatment process for improving structure uniformity of 20CrMoH sliding block blank

Abstract

The invention provides an online heat treatment process for improving the structure uniformity of a 20CrMoH sliding block blank, and relates to the technical field of material heat treatment processes. The process comprises the following steps: heating a steel blank from room temperature to austenitizing temperature for forging; the steel forging material is subjected to air cooling and then heated to be subjected to isothermal normalizing treatment, and a normalizing sliding block blank is obtained; and the normalized sliding block blank is rapidly cooled, then slowly cooled to the isothermal temperature, subjected to heat preservation and finally air-cooled to the room temperature, and the sliding block blank uniform in structure is obtained. According to the method, the structure uniformity of the sliding block blank is improved through normalizing treatment including cooling forging after austenitizing, heating after air cooling and rapid cooling + slow cooling + heat preservation treatment, machining and surface carburizing are further conducted subsequently, two-time phase change is conducted in total, bainite does not appear in the structure, and the banded structure grade is below the first grade; the method is simple and easy to operate, energy-saving, low in cost, short in process, high in efficiency and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of material heat treatment technology, in particular to an online heat treatment technology for improving the uniformity of the structure of a 20CrMoH slider blank. Background Art

[0002] 20CrMoH steel is often used to manufacture gears, shafts, and slider parts. The surface is subjected to severe friction during service, so it must have excellent comprehensive mechanical properties and surface wear resistance. It is often forged and then heat treated to obtain excellent comprehensive mechanical properties.

[0003] Since the addition of Cr element to 20CrMoH steel increases the hardenability, the cooling rate during heat treatment becomes the key point of process control. It should not be too fast, which will easily produce bainite structure, nor too slow, which will easily produce banded structure. In order to make the structure after heat treatment more uniform, without serious banded structure, and to save energy and reduce production costs, a new heat treatment process is needed.

[0004] Chinese patent publication number CN102605147A discloses a method of using the residual heat of forgings after forging for normalizing heat treatment. The invention application controls the forging deformation and the termination forging temperature of the last fire of the forging during the forging process, so that the final forging temperature of the forging is 20-30°C higher than the final forging temperature of the material, and then quickly cools to 650-700°C in the air, and then sends it to the heat treatment furnace to evenly heat the forging until the temperature inside and outside the forging is the same, and then heats to 60-50°C or higher than Ac3 or Acm of the material, and after the insulation reaches complete austenitization, it is cooled to room temperature at a certain cooling rate after being taken out of the furnace. In this method, the parts are quickly cooled to 650-700°C in the air after forging, and no phase transition from austenite to low-temperature structure occurs, which is not conducive to the homogenization of the structure. In addition, the cooling method after normalizing in this method is very easy to obtain a bainite structure with high hardness, which is not conducive to subsequent cutting processing and affects the cutting accuracy.

[0005] In the article "Effect of Isothermal Normalizing on the Cutting Performance of 20CrMo Steel" published by Yu Yingjie and other scholars, the heat treatment results in the isothermal temperature range of 500-630℃ were elaborated in detail. Although there is no bainite structure in the microstructure and the hardness is 172-174HB, the banding grade is relatively high, and isothermal normalizing directly after forging is prone to uneven structure.

[0006] The article "Improvement and Analysis of the Pre-heat Treatment Process of 20CrMo Steel" published by scholar Zhao Meihui uses stress relief annealing instead of isothermal annealing for pre-heat treatment of the steel after forging, which reduces the time of pre-heat treatment; however, this will reduce the service life of some tools during the cutting process.

[0007] The article "Elimination of banded structure in 20CrMoH steel forgings and control of its hardness" published by scholar Jie Pingkou disclosed that the banded structure in 20CrMoH steel forgings can be eliminated by isothermal annealing. It is necessary to effectively control the air cooling parameters such as the air temperature and air cooling time of the cold air process during the isothermal annealing process, and consider climatic factors; it can make the hardness of the forgings higher, which is also not conducive to subsequent cutting processing and affects the cutting accuracy.

[0008] In the article "Effects of Forging and Heat Treatment Processes on the Structure and Properties of 20CrMoH Steel" published by scholar Sui Xiaoli, it is disclosed that the banded structure can be eliminated by controlling the forging ratio, upsetting ratio and drawing ratio within a certain range. After the subsequent preliminary heat treatment process including normalizing, the hardness at 920°C is between 201-202HBW. Obviously, the hardness is relatively large, which is not conducive to subsequent cutting processing and affects the cutting accuracy. Summary of the invention

[0009] In order to solve the technical problems in the prior art that 20CrMoH steel is prone to bainite structure, high banding level, uneven structure after forging, and high hardness after isothermal annealing, stress relief annealing or normalizing heat treatment of forging materials, which is not conducive to subsequent cutting processing, subsequent machining and surface carburization of slider blanks, etc.; the present invention proposes an online heat treatment process that can solve the above problems and improve the uniformity of the structure of 20CrMoH slider blanks. The technical solution is as follows:

[0010] An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, the online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank comprises the following steps:

[0011] S1. Cooling and forging after austenitizing: heating the 20CrMoH steel billet from room temperature to austenitizing temperature and keeping the temperature, and then air cooling and forging to obtain a 20CrMoH slider billet;

[0012] S2, normalizing treatment after air cooling and heating: after forging, the 20CrMoH slider blank in S1 is air cooled and then heated for isothermal normalizing treatment to obtain a normalized 20CrMoH slider blank;

[0013] S3, rapid cooling + slow cooling + insulation treatment: After normalizing, the normalized 20CrMoH slider blank in S2 is rapidly cooled, then slowly cooled to an isothermal temperature, insulation is performed, and finally air-cooled to room temperature to obtain a 20CrMoH slider blank with uniform structure.

[0014] Optionally, in S1, the heating rate from room temperature to austenitizing temperature is 1-10°C / s, the austenitizing temperature is 950-1200°C, the holding time is 5min-4h, and the temperature is air-cooled to 900-1150°C for forging.

[0015] Optionally, the structure of the 20CrMoH slider blank in S1 is all austenite structure.

[0016] Optionally, S2 is air-cooled to a temperature of 450-500°C, and then heated to 920°C at a rate of 1-10°C / s. The holding time is calculated according to the normalizing holding time calculation formula, and the austenitization of the 20CrMoH slider blank is completed again.

[0017] Optionally, the holding time in S2 is calculated according to the normalizing holding time calculation formula: t=αkD; wherein: t is the holding time, the unit is min, α is the heating coefficient, k is the correction coefficient during heating, and D is the effective thickness of the part, the unit is min.

[0018] Optionally, the structure of the normalized 20CrMoH slider blank in S2 is an austenite structure.

[0019] Optionally, in S3, the temperature is quickly cooled to 700°C with a cooling rate of 1-3°C / s; and the temperature is slowly cooled to an isothermal temperature with a cooling rate of 0.5°C / s.

[0020] Optionally, the isothermal temperature in S3 is 630°C and the holding time is 20min-3h. The specific holding time is determined by the specific part size and the part TTT curve.

[0021] Optionally, the uniformly structured 20CrMoH slider blank in S3 has a ferrite plus pearlite structure, no bainite structure is produced in the structure, and the banded structure is rated below level 1.

[0022] Optionally, the Vickers hardness of the uniformly structured 20CrMoH slider blank in S3 is 160-190 HV, and subsequent machining and surface carburizing are required.

[0023] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0024] The above scheme proposes an online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank, which can solve the technical problems in the prior art that 20CrMoH steel is prone to bainite structure, high banding level, uneven structure after forging, and high hardness after isothermal annealing, stress relief annealing or normalizing heat treatment of the forging material, which is not conducive to subsequent machining and surface carburization of the slider blank.

[0025] The present invention can obtain the shape and size of the slider blank by forging after cooling down after austenitization; can obtain more uniform austenite grains by normalizing treatment after air cooling; and can reduce the level of banded structure by rapid cooling + slow cooling + heat preservation treatment, ensuring that ferrite + pearlite structure is obtained without bainite structure.

[0026] The Vickers hardness of the uniformly structured 20CrMoH slider blank prepared by the present invention is 160-190 HV. The 20CrMoH slider blank is not a final product. The blank needs to be machined and surface carburized after heat treatment, so the structure requirement is ferrite plus pearlite structure, no bainite structure is produced in the structure, and the banded structure rating is below level 1.

[0027] In summary, compared with other traditional methods, the method of the present invention prepares a 20CrMoH slider blank with uniform structure through cooling forging after austenitizing, normalizing treatment of heating after air cooling, and rapid cooling + slow cooling + insulation treatment. A total of two phase changes are carried out, bainite does not appear in the structure, and the banded structure level is below level 1; the method is simple and easy to operate, saves energy, has low cost, short process, high efficiency, and is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a heat treatment process diagram of an online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank according to the present invention;

[0030] Figure 2 The microstructure diagram of a 20CrMoH slider blank prepared by an online heat treatment process for improving the uniformity of the 20CrMoH slider blank structure of the present invention;

[0031] Figure 3 This is a common normalizing heat treatment process diagram of 20CrMoH steel in comparative example 1;

[0032] Figure 4 This is a microstructure diagram of the 20CrMoH slider blank after ordinary normalizing heat treatment in Example 1;

[0033] Figure 5 This is a process diagram of residual heat normalizing heat treatment of 20CrMoH steel after forging in comparative example 2;

[0034] Figure 6 This is the microstructure diagram of the 20CrMoH slider blank after the residual heat normalizing heat treatment of the 20CrMoH steel after forging in Example 2. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0036] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0037] In the embodiments of the present invention, "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings they intend to express are consistent.

[0038] In the embodiments of the present invention, sometimes the subscripts such as W 1 It may be written in non-subscript form such as W1. When the difference is not emphasized, the meaning is the same.

[0039] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0040] An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, the online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank comprises the following steps:

[0041] S1. Cooling and forging after austenitizing: heating the 20CrMoH steel billet from room temperature to austenitizing temperature and keeping the temperature, and then air cooling and forging to obtain a 20CrMoH slider billet;

[0042] S2, normalizing treatment after air cooling and heating: after forging, the 20CrMoH slider blank in S1 is air cooled and then heated for isothermal normalizing treatment to obtain a normalized 20CrMoH slider blank;

[0043] S3, rapid cooling + slow cooling + insulation treatment: After normalizing, the normalized 20CrMoH slider blank in S2 is rapidly cooled, then slowly cooled to an isothermal temperature, insulation is performed, and finally air-cooled to room temperature to obtain a 20CrMoH slider blank with uniform structure.

[0044] In particular, the heating rate from room temperature to austenitizing temperature in S1 is 1-10°C / s, the austenitizing temperature is 950-1200°C, the holding time is 5min-4h, and the temperature is air-cooled to 900-1150°C for forging.

[0045] In particular, the structure of the 20CrMoH slider blank in S1 is all austenite structure.

[0046] In particular, S2 is air-cooled to a temperature of 450-500°C, and then heated to 920°C at a rate of 1-10°C / s. The holding time is calculated according to the normalizing holding time calculation formula, and the austenitization of the 20CrMoH slider blank is completed again.

[0047] Optionally, the holding time in S2 is calculated according to the normalizing holding time calculation formula: t=αkD; wherein: t is the holding time, the unit is min, α is the heating coefficient, k is the correction coefficient during heating, and D is the effective thickness of the part, the unit is min.

[0048] In particular, the structure of the normalized 20CrMoH slider blank in S2 is austenite structure, and there is no special requirement for the austenite grain size.

[0049] In particular, in S3, the temperature is rapidly cooled to 700°C with a cooling rate of 1-3°C / s; and the temperature is slowly cooled to an isothermal temperature with a cooling rate of 0.5°C / s.

[0050] In particular, the isothermal temperature in S3 is 630°C and the holding time is 20min-3h. The specific holding time is determined by the specific part size and based on the part TTT curve.

[0051] In particular, the uniformly organized 20CrMoH slider blank in S3 has a ferrite plus pearlite structure, no bainite structure is produced in the structure, and the banded structure is rated below level 1.

[0052] In particular, the Vickers hardness of the uniformly structured 20CrMoH slider blank in S3 is 160-190 HV, and subsequent machining and surface carburizing are required.

[0053] Example 1

[0054] An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, the online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank is combined with Figure 1 Follow these steps:

[0055] S1. Cooling forging after austenitization: Using Gleeble-3800 thermal simulation test machine, The 20CrMoH steel blank is placed in the sample chamber and evacuated; the temperature is raised from room temperature to the austenitizing temperature and kept at this temperature, the heating rate is 10°C / s, the austenitizing temperature is 950°C, the holding time is 5 min, and the sample is cooled to 900°C at a rate of 1°C / s and compressed by 30% to simulate the forging of 20CrMoH steel, thereby obtaining a 20CrMoH slider blank; the microstructure of the 20CrMoH slider blank is all austenite structure;

[0056] S2. Normalizing treatment after air cooling: After forging, the 20CrMoH slider blank in S1 is cooled to 500°C at a cooling rate of 0.5°C / s in coordination with resistance heating, and then heated to 920°C at a rate of 10°C / s for isothermal normalizing treatment. The holding time is calculated as 5 minutes according to the normalizing holding time calculation formula: t=αkD, and the normalized 20CrMoH slider blank is obtained; the microstructure of the normalized 20CrMoH slider blank is austenite, and there is no special requirement for grain size;

[0057] S3, rapid cooling + slow cooling + insulation treatment: After normalizing, the normalized 20CrMoH slider blank in S2 is rapidly cooled to 700°C with a cooling rate of 1°C / s; then slowly cooled to an isothermal temperature of 630°C with a cooling rate of 0.5°C / s, and insulation is performed. The insulation time is determined by the specific part size and the part TTT curve to be 20 minutes. Air is used as the cooling medium, and the sample is air-cooled from 630°C to room temperature in the sample chamber to obtain a 20CrMoH slider blank with uniform structure.

[0058] like Figure 2 As shown, the uniformly organized 20CrMoH slider blank prepared in this embodiment is in the shape of a rod, and its microstructure is a ferrite plus pearlite structure, no bainite structure is produced in the structure, and the banded structure is rated as 0.5.

[0059] The Vickers hardness of the uniformly structured 20CrMoH slider blank prepared in this embodiment is 168.5-170.1 HV, and subsequent machining and surface carburization are required.

[0060] Comparative Example 1

[0061] An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, the online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank is combined with Figure 3 Follow these steps:

[0062] S1. Forging material preparation: Use a tubular furnace to After forging, the 20CrMoH steel bar is cooled to room temperature and placed in a tube furnace for vacuuming. The microstructure of the 20CrMoH slider blank is all austenite.

[0063] S2. Ordinary normalizing process: the forged sample slider blank is heated from room temperature to 950-1200℃ at 10℃ / s and kept warm for 20min. This is the complete austenitization process of 20CrMoH steel components. The temperature is 30-50℃ above the normalizing process temperature Ac3 and is set according to the phase diagram temperature. The microstructure of the normalized 20CrMoH slider blank is austenite structure, and there is no requirement for grain size.

[0064] S3. Air cooling treatment: Take out the normalized 20CrMoH slider blank and air cool it to room temperature. This is to simulate the air cooling treatment during on-site production.

[0065] like Figure 4 As shown, the microstructure of the 20CrMoH slider blank prepared in this comparative example is ferrite, pearlite and bainite, and the banded structure is rated as 1.5.

[0066] The Vickers hardness of the 20CrMoH slider blank prepared in this comparative example is 259.4-276.2 HV, and subsequent machining and surface carburization are required.

[0067] Comparative Example 2

[0068] An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, the online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank is combined with Figure 5 Follow these steps:

[0069] S1. Forging material preparation: Use a tubular furnace to The 20CrMoH steel blank is placed in the sample chamber and evacuated; the temperature is raised from room temperature to the austenitizing temperature and kept at this temperature, the heating rate is 10°C / s, the austenitizing temperature is 950°C, the holding time is 5 min, and the sample is cooled to 900°C at a rate of 1°C / s and compressed by 30% to simulate the forging of 20CrMoH steel, thereby obtaining a 20CrMoH slider blank; the microstructure of the 20CrMoH slider blank is a completely austenitic structure;

[0070] S2, ordinary normalizing process: after forging, the 20CrMoH slider blank in S1 is cooled to 700℃ at a cooling rate of 1℃ / s in coordination with resistance heating, and then cooled to 630℃ at a cooling rate of 0.5℃ / s, and isothermal normalizing is performed. The holding time is 20min to obtain a normalized 20CrMoH slider blank; the microstructure of the normalized 20CrMoH slider blank is austenite, and there is no requirement for grain size;

[0071] S3. Insulation treatment: After normalizing, the 20CrMoH slider blank normalized in S2 is cooled from 630°C to room temperature in the sample chamber using air as a cooling medium to obtain a 20CrMoH slider blank.

[0072] like Figure 6 As shown, the microstructure of the 20CrMoH slider blank prepared in this comparative example is ferrite plus pearlite structure, without bainite structure, and the banded structure is rated as level 1.

[0073] The Vickers hardness of the 20CrMoH slider blank prepared in this comparative example is 170.3-173.5 HV, and subsequent machining and surface carburization are required.

[0074] Comparing Comparative Examples 1-2 with Example 1, it is found that the banded structure of the samples treated by the heat treatment process of the present invention is below level 1, the structure is ferrite and pearlite, there is no bainite structure, the Vickers hardness is 160-190HV, and the structure and performance are conducive to subsequent processing. Compared with the traditional normalizing process, the microstructure and performance are more excellent, and compared with the post-forging residual heat normalizing process, the banded structure level is reduced.

[0075] The above scheme proposes an online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank, which can solve the technical problems in the prior art that 20CrMoH steel is prone to bainite structure, high banding level, uneven structure after forging, and high hardness after isothermal annealing, stress relief annealing or normalizing heat treatment of the forging material, which is not conducive to subsequent machining and surface carburization of the slider blank.

[0076] The present invention can obtain the shape and size of the slider blank by forging after cooling down after austenitization; can obtain more uniform austenite grains by normalizing treatment after air cooling; and can reduce the level of banded structure by rapid cooling + slow cooling + heat preservation treatment, ensuring that ferrite + pearlite structure is obtained without bainite structure.

[0077] The Vickers hardness of the uniformly structured 20CrMoH slider blank prepared by the present invention is 160-190 HV. The 20CrMoH slider blank is not a final product. The blank needs to be machined and surface carburized after heat treatment, so the structure requirement is ferrite plus pearlite structure, no bainite structure is produced in the structure, and the banded structure rating is below level 1.

[0078] In summary, compared with other traditional methods, the method of the present invention prepares a 20CrMoH slider blank with uniform structure through cooling forging after austenitizing, normalizing treatment of heating after air cooling, and rapid cooling + slow cooling + insulation treatment. A total of two phase changes are carried out, bainite does not appear in the structure, and the banded structure level is below level 1; the method is simple and easy to operate, saves energy, has low cost, short process, high efficiency, and is conducive to large-scale industrial production and promotion.

[0079] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0080] In the present invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0081] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0082] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An online heat treatment process for improving the uniformity of the structure of a 20CrMoH slider blank, characterized in that: The online heat treatment process for improving the uniformity of the 20CrMoH slider blank structure is as follows: S1. Cooling and forging after austenitizing: heating the 20CrMoH steel billet from room temperature to austenitizing temperature and keeping the temperature, and then air cooling and forging to obtain a 20CrMoH slider billet; S2, normalizing treatment after air cooling and heating: after forging, the 20CrMoH slider blank in S1 is air cooled and then heated for isothermal normalizing treatment to obtain a normalized 20CrMoH slider blank; S3, rapid cooling + slow cooling + insulation treatment: After normalizing, the normalized 20CrMoH slider blank in S2 is rapidly cooled, then slowly cooled to an isothermal temperature, insulation is performed, and finally air-cooled to room temperature to obtain a 20CrMoH slider blank with uniform structure.

2. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: In S1, the heating rate from room temperature to austenitizing temperature is 1-10°C / s, the austenitizing temperature is 950-1200°C, the holding time is 5min-4h, and the temperature is cooled to 900-1150°C by air cooling for forging.

3. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: The structure of the 20CrMoH slider blank in S1 is all austenite.

4. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: S2 is air-cooled to a temperature of 450-500°C, and then heated to 920°C at a rate of 1-10°C / s. The holding time is calculated according to the normalizing holding time calculation formula to complete the austenitization of the 20CrMoH slider blank again.

5. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: The holding time in S2 is calculated according to the normalizing holding time calculation formula: t=αkD; where: t is the holding time, the unit is min, α is the heating coefficient, k is the correction coefficient during heating, and D is the effective thickness of the part, the unit is min.

6. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: The structure of the normalized 20CrMoH slider blank in S2 is austenite.

7. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1 is characterized in that: In S3, the temperature is quickly cooled to 700°C at a cooling rate of 1-3°C / s; the temperature is slowly cooled to an isothermal temperature at a cooling rate of 0.5°C / s.

8. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1, characterized in that: The medium temperature in S3 is 630℃, and the holding time is 20min-3h. The specific holding time is determined by the specific part size and the part TTT curve.

9. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1, characterized in that: The structure of the uniformly organized 20CrMoH slider blank in S3 is ferrite plus pearlite, no bainite is produced in the structure, and the banded structure is rated below level 1.

10. The online heat treatment process for improving the uniformity of the structure of the 20CrMoH slider blank according to claim 1, characterized in that: The Vickers hardness of the uniformly structured 20CrMoH slider blank in S3 is 160-190 HV, and subsequent machining and surface carburizing are required.

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