High-temperature deformation heat treatment process for forgings

Abstract

The application relates to a forging high-temperature deformation heat treatment process, which comprises the following steps: a precooling step, a quenching step, a heat preservation step and a tempering step, a forged piece after heat shaping is cooled to a preliminary temperature T1; in the quenching step, the forged piece after cooling is cooled in a quenching medium, the temperature of the quenching medium is less than or equal to 50 DEG C; in the heat preservation step, the forged piece after quenching is preserved for 4-6 hours; and in the tempering step, tempering is carried out at a temperature T2 for 2-4 hours. The forged piece produced by the process can meet the technical requirements of hardness, grain size, metallographic structure and the like and no cracks occur, the forging high-temperature deformation heat treatment process can reduce some steps in the related technology, reduce the cost and reduce the processing period.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of forging heat treatment technology, and particularly relates to a high-temperature deformation heat treatment process for forgings. BACKGROUND

[0002] The passenger car steering knuckle die forging has a thick middle part and multiple branches around the middle part, so the passenger car steering knuckle die forging has a complex geometric shape, a large height difference, and a large difference in thickness (6 mm at the thinnest position). The passenger car steering knuckle die forging is usually made of alloy structural steel 40Cr. After processing, the passenger car steering knuckle die forging requires quenching and tempering grain size of greater than or equal to 5 levels, metallographic structure of 1 level to 4 levels, and heat treatment hardness of HRC 26-32. The conventional heat treatment process is as follows: bar (heating) -> blanking -> pre-forging -> final forging -> hot shaping -> heating (normalizing) -> cooling -> cold shaping -> heating (quenching) -> cooling -> tempering.

[0003] After the final forging and shaping of the passenger car steering knuckle, the passenger car steering knuckle needs to be heated to AC3+30-50 (℃) and air-cooled for 2-3 hours, and then cold-shaped. Then, the passenger car steering knuckle needs to be heated to AC3+30-50 (℃) and air-cooled for 2-3 hours, and then oil-cooled to 70-100 (℃). Finally, the passenger car steering knuckle needs to be tempered at a temperature of 550-650 (℃) for 2-4 hours. Due to the complex geometric shape and large thickness difference of the passenger car steering knuckle die forging, the existing technical steps are prone to cause cracks in the passenger car steering knuckle die forging during processing. In addition, the existing technology usually takes 17-18 hours, and the steps are too many and too cumbersome, so a large amount of energy and production time are wasted, and the cost is increased. SUMMARY

[0004] The purpose of the present application is to provide a high-temperature deformation heat treatment process for forgings. The forgings produced by the process can meet the technical requirements of hardness, grain size, metallographic structure, etc. and have no cracks. The high-temperature deformation heat treatment process for forgings can reduce some steps in the related technology, reduce the cost, and reduce the processing cycle.

[0005] To this end, the present application provides a high-temperature deformation heat treatment process for forgings, which includes the following steps: a pre-cooling step of cooling the forgings after hot shaping to a preliminary temperature T1; a quenching step of cooling the cooled forgings in a quenching medium, the temperature of the quenching medium being less than or equal to 50 (℃); a heat preservation step of heat preserving the quenched forgings for 4-6 hours; and a tempering step of tempering at a temperature T2 for 2-4 hours.

[0006] In one possible implementation, the chemical composition of the forgings includes 0.37%≤C≤0.44%, 0.17%≤Si≤0.37%, 0.5%≤Mn≤0.8%, P≤0.035%, S≤0.035%, 0.8%≤Cr≤1.1%, Ni≤0.3%, and Cu≤0.25%.

[0007] In a possible implementation, the preliminary temperature T1 = phase transition temperature AC3 of the forging + (20℃-120℃); the phase transition temperature AC3 = 903-233.7W C +438.5W P +30.49W Si +37.92W v -34.43W Mn -23W Ni -200(W C -0.54+0.06W Ni )(℃).

[0008] In a possible implementation, the cooling time in the precooling step is 20s-50s.

[0009] In a possible implementation, the cooling mode used in the precooling step is air cooling.

[0010] In a possible implementation, the cooling time in the quenching step is 10s-20s.

[0011] In a possible implementation, the medium in the quenching step is water.

[0012] In a possible implementation, the temperature in the holding step is 200℃-500℃.

[0013] In a possible implementation, the tempering temperature T2 is 580℃-650℃.

[0014] According to the forging high-temperature deformation heat treatment process provided in the embodiments of the present application, the forging high-temperature deformation heat treatment process comprises a precooling step, a quenching step, a holding step and a tempering step, and the forging after heat shaping is cooled to a preliminary temperature T1; in the quenching step, the cooled forging is cooled in a quenching medium, and the temperature of the quenching medium is less than or equal to 50℃; in the holding step, the quenched forging is held for 4 hours-6 hours; and in the tempering step, the forging is tempered at a temperature T2 for 2 hours-4 hours. The forging produced by the process can meet the technical requirements of hardness, grain size, metallographic structure and the like and no cracks occur, the forging high-temperature deformation heat treatment process can reduce some steps in the related technology, reduce the cost and reduce the processing period. BRIEF DESCRIPTION OF DRAWINGS

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, in the drawings, the same parts use the same reference numerals, and the drawings are not drawn to scale.

[0016] Figure 1 The metallographic image provided in Embodiment 1 of this application is shown. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] This invention provides a high-temperature deformation heat treatment process for forgings, which includes the following process flow: pre-cooling step, quenching step, heat holding step, and tempering step.

[0020] In the method described in this invention, the forging undergoes multiple steps in the high-temperature deformation heat treatment process, such as: bar stock (heating) → billet preparation → pre-forging → final forging → hot forming. The hot-formed forging is then processed through a high-temperature deformation heat treatment process, which includes a pre-cooling step, where the hot-formed forging is directly cooled in the pre-cooling step; after the pre-cooling step, the forging enters the quenching step, where it is placed in a quenching medium for quenching and cooling; after being placed in the cooling medium for a period of time, it enters the heat preservation step for heat preservation, where the forging can be placed in a heat preservation device. The heat preservation device can be sealed to reduce temperature loss from the forging, or it can be heated to maintain a constant temperature within the device's cavity; after heat preservation, the forging is then tempered.

[0021] The time required for forgings to undergo pre-cooling, quenching, holding, and tempering steps is between 6 and 10 hours. Compared to existing high-temperature deformation processes, this application reduces production time and the number of steps required for forgings, thereby lowering production costs. Furthermore, forgings produced through these steps meet the requirements of a tempered grain size ≥5, a microstructure of grade 1 to 4, and a heat treatment hardness of HRC 26-32. The forgings are also less prone to cracking, thus improving their quality.

[0022] Furthermore, in the pre-cooling step, the hot-shaped forging needs to be cooled to T1. In the quenching step, the forging needs to be placed in a quenching medium, which can be either oil or water. The temperature of the quenching medium should be less than or equal to 50°C. When the temperature of the quenching medium exceeds 50°C, the forging is prone to cracking. In the holding step, the quenched forging needs to be held at that temperature for 4-6 hours. The holding time can be any of 4, 5, or 6 hours. Due to the complex shape and significant thickness variations of the forging, the holding step helps prevent excessive temperature in different parts of the forging, eliminates some stress, and thus prevents cracking. If the holding time is less than 4 hours, the stress elimination in the forging is insufficient, leading to cracking or the formation of fissures, and the metallographic structure and tempered grain size will be inadequate. When the holding time is greater than 6 hours, it will cause energy waste and increase the manufacturing cycle. In the tempering step, the forging is tempered at temperature T2 for 2 to 4 hours. The tempering time can be any time between 2 hours, 3 hours or 4 hours.

[0023] In some optional examples, the chemical composition of the forging includes: 0.37% ≤ C ≤ 0.44%, 0.17% ≤ Si ≤ 0.37%, 0.5% ≤ Mn ≤ 0.8%, P ≤ 0.035%, S ≤ 0.035%, 0.8% ≤ Cr ≤ 1.1%, Ni ≤ 0.3%, and Cu ≤ 0.25%. The remaining components of the forging are Fe and impurities, and the forging is 40Cr alloy structural steel. After treating the 40Cr alloy structural steel through pre-cooling, quenching, heat treatment, and tempering steps, the 40Cr alloy structural steel meets the conditions of tempered grain size ≥ 5, metallographic structure of grade 1 to 4, and high fracture resistance of 26-32, thus preventing the occurrence of fracture or cracks in the 40Cr alloy structural steel. However, the above steps are not limited to 40Cr alloy structural steel.

[0024] Initial temperature T1 = Phase transformation temperature of the forging AC3 + (20℃ - 120℃); Phase transformation temperature AC3 = 903 - 233.7W C +438.5W P +30.49W Si +37.92Wv -34.43W Mn -23W Ni -200(W C -0.54 +0.06W Ni (℃).

[0025] The phase transformation temperature AC3 is related to the composition of the forging. In the national standard GB-T699, the phase transformation temperature of 40Cr alloy structural steel is 800℃. When the composition of 40Cr alloy structural steel fluctuates, its phase transformation temperature also fluctuates by about ±10℃. This fluctuation range is small and negligible; therefore, the phase transformation temperature of the forging is based on 800℃. The initial temperature T1 can be the phase transformation temperature AC3 of the forging plus 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, or 120℃. Specifically, the initial temperature can be 820℃-920℃. It can be seen that the fluctuation range of the initial temperature T1 is within 100℃, which is larger than the processing temperature of 830-850℃ in related technologies, making it easier for operators to control the pre-cooling process. When the initial temperature is less than 820℃, the hardness and metallographic structure of the forgings are insufficient. When the initial temperature is greater than 920℃, the forgings are prone to cracking and the tempering grain size is insufficient.

[0026] In some embodiments, the cooling time in the precooling step is 20-50 seconds. There is no specific limitation on the cooling time in the precooling step, as long as the forging is cooled to the initial temperature T1. The preferred cooling time is 20-50 seconds, specifically 20, 30, 40, or 50 seconds. In the precooling step, a cooling time of less than 20 seconds results in insufficient cooling, causing the initial temperature T1 to be greater than 920°C; a cooling time greater than 50 seconds results in overcooling, causing the initial temperature T1 to be less than 820°C.

[0027] In some embodiments, air cooling is used in the pre-cooling step. Air cooling reduces the impact of external objects on the forging during pre-cooling. There are no special restrictions on the speed and power of air cooling; it is sufficient to cool the final forging to the initial temperature T within 20-50 seconds. The speed and power of air cooling can be adjusted according to specific weather and temperature conditions. The air cooling speed and power are lower in winter than in summer.

[0028] In some examples, the cooling time in the quenching step is 10-20 seconds. Specifically, the cooling time is 10 seconds, 15 seconds, or 20 seconds. In the quenching step, if the cooling time is less than 10 seconds, the cooling is insufficient, resulting in inadequate hardness and metallographic structure of the forging. If the cooling time is greater than 20 seconds, the cooling is excessive, making the forging prone to cracking.

[0029] In some embodiments, the medium used in the quenching step is water. Compared to using oil as the quenching medium, using water reduces the processing cost of the forgings for the factory. There are no special restrictions on the flow rate of the quenching medium, as long as it can cool the forgings within a specified time.

[0030] In some embodiments, the temperature during the heat preservation step is 200℃-500℃. When the heat preservation temperature is less than 200℃, the stress relief of the forging is insufficient, which may lead to cracking or fissures in the forging, and the metallographic structure grade is not up to standard. When the heat preservation temperature is greater than 500℃, the metallographic structure grade, grain size grade, and hardness are not up to standard.

[0031] In some embodiments, the tempering temperature T2 is 580℃-650℃. Specifically, the quenching temperature is 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, or 650℃. There is a one-to-one correspondence between tempering temperature and hardness HB, meaning that tempering within the 580℃-650℃ range will result in a hardness of HRC 26-32. When the tempering temperature is below 580℃ or above 650℃, the hardness HRC will be too low or too high, failing to meet the requirements of the forging.

[0032] A forging, after being treated by any of the above-mentioned high-temperature deformation heat treatment processes, achieves the following effects: tempered grain size ≥ 5, metallographic structure of grade 1 to 4, and hardness of HRC26-32, and the forging is not prone to cracking.

[0033] The present application will be described in detail below through embodiments, but the scope of protection of the present application is not limited thereto.

[0034] Example 1

[0035] This embodiment is used to illustrate the high-temperature deformation heat treatment process for forgings.

[0036] The processing technology adopts the following steps:

[0037] The pre-cooling step involves cooling the hot-formed forging to a preliminary temperature T1.

[0038] Quenching step: Cool the cooled forging in water at a temperature of less than or equal to 50°C;

[0039] The heat preservation step involves keeping the quenched forgings at a heat level for 4 hours.

[0040] Tempering procedure: Temper at 580℃ for 2 hours.

[0041] Specifically, taking the total weight of the forgings as 100%, the forgings are passenger car steering knuckle forgings made of 40Cr alloy structural steel. The matrix of the forgings is Fe, and the chemical composition of the forgings also includes: 0.37%≤C≤0.44%, 0.17%≤Si≤0.37%, 0.5%≤Mn≤0.8%, P≤0.035%, S≤0.035%, 0.8%≤Cr≤1.1%, Ni≤0.3%, and Cu≤0.25%.

[0042] In the pre-cooling step, air cooling is used, and the cooling time is 50 seconds, so that the initial temperature T1 = AC3 + 20℃; in the quenching step, the quenching cooling time is 10 seconds; in the heat preservation step, the heat preservation temperature is 200℃.

[0043] Example 2

[0044] This embodiment is used to illustrate the high-temperature deformation heat treatment process for forgings.

[0045] The processing technology adopts the following steps:

[0046] The pre-cooling step involves cooling the hot-formed forging to a preliminary temperature T1.

[0047] Quenching step: Cool the cooled forging in water at a temperature of less than or equal to 50°C;

[0048] The heat preservation step involves keeping the quenched forgings at a heat level for 5 hours.

[0049] Tempering procedure: Temper at 600℃ for 3 hours.

[0050] Specifically, taking the total weight of the forgings as 100%, the forgings are passenger car steering knuckle forgings made of 40Cr alloy structural steel. The matrix of the forgings is Fe, and the chemical composition of the forgings also includes: 0.37%≤C≤0.44%, 0.17%≤Si≤0.37%, 0.5%≤Mn≤0.8%, P≤0.035%, S≤0.035%, 0.8%≤Cr≤1.1%, Ni≤0.3%, and Cu≤0.25%.

[0051] In the pre-cooling step, air cooling is used, and the cooling time is 30 seconds, so that the initial temperature T1 = AC3 + 80℃; in the quenching step, the quenching cooling time is 15 seconds; in the heat preservation step, the heat preservation temperature is 300℃.

[0052] Example 3

[0053] This embodiment is used to illustrate the high-temperature deformation heat treatment process for forgings.

[0054] The processing technology adopts the following steps:

[0055] The pre-cooling step involves cooling the hot-formed forging to a preliminary temperature T1.

[0056] Quenching step: Cool the cooled forging in water at a temperature of less than or equal to 50°C;

[0057] The heat preservation step involves keeping the quenched forgings at a heat level for 6 hours.

[0058] Tempering procedure: Temper at 650℃ for 4 hours.

[0059] Specifically, taking the total weight of the forgings as 100%, the forgings are passenger car steering knuckle forgings made of 40Cr alloy structural steel. The matrix of the forgings is Fe, and the chemical composition of the forgings also includes: 0.37%≤C≤0.44%, 0.17%≤Si≤0.37%, 0.5%≤Mn≤0.8%, P≤0.035%, S≤0.035%, 0.8%≤Cr≤1.1%, Ni≤0.3%, and Cu≤0.25%.

[0060] In the pre-cooling step, air cooling is used, and the cooling time is 20 seconds, so that the initial temperature T1 = AC3 + 120℃; in the quenching step, the quenching cooling time is 20 seconds; in the heat preservation step, the heat preservation temperature is 500℃.

[0061] Comparative Example 1

[0062] The method was implemented according to Example 1, except that the quenching medium cooling time was 5 seconds.

[0063] Comparative Example 2

[0064] The method was implemented according to Example 1, except that the quenching medium cooling time was 25 seconds.

[0065] Comparative Example 3

[0066] The method was carried out according to Example 1, except that the temperature of the quenching medium was 55°C.

[0067] Comparative Example 4

[0068] The method of Example 1 was implemented, except that the cooling time of the forging in the pre-cooling step was greater than 50s, and the initial temperature T1 was equal to the phase transformation temperature AC3 + 10℃ of the forging.

[0069] Comparative Example 5

[0070] The method of Example 1 is implemented, except that the cooling time of the forging in the pre-cooling step is less than 20s, and the initial temperature T1 is equal to the phase transformation temperature AC3 + 130℃ of the forging.

[0071] Comparative Example 6

[0072] The method was implemented according to Example 1, except that the heat preservation time in the heat preservation step was 3 hours.

[0073] Comparative Example 7

[0074] The method was implemented according to Example 1, except that the heat preservation temperature in the heat preservation step was 150°C.

[0075] Comparative Example 8

[0076] The method was implemented according to Example 1, except that the heat preservation temperature in the heat preservation step was 550°C.

[0077] According to the national standard GB-T699, the forgings in Examples 1-3 and Comparative Examples 1-8 are made of 40Cr alloy structural steel. According to the national standard, the phase transformation temperature of 40Cr alloy structural steel fluctuates between 820℃ and 920℃. The variation in the composition of 40Cr alloy structural steel has little impact on the phase transformation temperature, that is, it has little impact on the initial temperature in the pre-cooling step. In other words, the phase transformation temperature of 40Cr alloy structural steel is 800℃.

[0078] The phase transformation temperature of 800℃ for 40Cr alloy structural steel in the national standard GB-T699 was used as a benchmark to determine the temperature values ​​for the pre-cooling step.

[0079] The phase transition temperatures and initial temperatures of Examples 1-3 and Comparative Examples 1-8 are shown in Table 1.

[0080] Table 1 Phase transition temperature and initial temperature

[0081] Number AC3 transformation temperature preliminary temperature T1 Example 1 800℃ 820℃ Example 2 800℃ 880℃ Example 3 800℃ 920℃ Comparative Example 1 800℃ 820℃ Comparative Example 2 800℃ 820℃ Comparative Example 3 800℃ 820℃ Comparative Example 4 800℃ 810℃ Comparative Example 5 800℃ 930℃ Comparative Example 6 800℃ 820℃ Comparative Example 7 800℃ 820℃ Comparative Example 8 800℃ 820℃

[0082] The grain size was tested using the method of national standard GB / T6394-2002, the metallographic structure was tested using the method of national standard GB / T13320-2007, and the hardness was tested using the method of national standard GB / T231.1-2009. The test results of the tempered grain size, metallographic structure, and HB of Examples 1-3 and Comparative Examples 1-8 are shown in Table 2.

[0083] Table 2 Test Results of Forgings

[0084]

[0085]

[0086] See Table 2 and Figure 1 It can be seen that, Figure 1The metallographic diagram provided in Embodiment 1 of this application is shown. The forgings in Embodiments 1-3 all meet the requirements of tempering grain size ≥ 5, metallographic structure 1-4, and hardness HRC 26-32. Therefore, it can be seen that the forgings meet the required requirements after undergoing the pre-cooling, quenching, and tempering steps.

[0087] Referring to Table 2, when the quenching medium cooling time is less than 10 seconds, the test results of the forged parts show that the metallographic structure grade is insufficient and the hardness is insufficient, failing to meet the requirements. When the quenching time is greater than 20 seconds, the test results of the forged parts show cracks, failing to meet the requirements. When the temperature of the quenching medium is greater than 50℃, the test results of the forged parts show cracks, failing to meet the requirements.

[0088] When the cooling time of the forging in the pre-cooling step is greater than 50 seconds and the initial temperature T1 is less than the phase transformation temperature AC3 + 20℃ of the forging, the test results of the forged forging show that the tempered grain size and metallographic structure are insufficient, and the hardness of the forging is insufficient, failing to meet the required requirements. When the cooling time of the forging in the pre-cooling step is less than 20 seconds and the initial temperature T1 is greater than the phase transformation temperature AC3 + 120℃ of the forging, the test results of the forged forging show cracks, failing to meet the required requirements.

[0089] When the heat preservation time in the heat preservation step is less than 4 hours, the test results of the forged parts show that the tempered grain size grade and metallographic structure grade are insufficient, and cracks are also present, which does not meet the requirements.

[0090] When the holding temperature during the heat treatment step is less than 200℃, the test results of the forged parts show that the metallographic structure grade is insufficient and cracks are present, failing to meet the requirements. When the holding temperature during the heat treatment step is greater than 500℃, the test results of the forged parts show that the tempered grain size grade and metallographic structure grade are insufficient, and the hardness of the forgings is insufficient, failing to meet the requirements.

[0091] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0092] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0093] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0094] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high-temperature deformation heat treatment process for forgings, characterized in that, include: The pre-cooling step involves cooling the hot-formed forging to a preliminary temperature T1, where the preliminary temperature T1 = the phase transformation temperature AC3 of the forging + (20℃-120℃). The quenching step involves cooling the cooled forging in a quenching medium with a temperature of less than or equal to 50°C. The medium in the quenching step is water. The heat preservation step involves keeping the quenched forgings at a constant temperature for 4 to 6 hours, with the heat source coming from the residual heat of the quenched forgings. The tempering process involves holding the material at temperature T2 for 2-4 hours. The temperature during the heat preservation step is 200℃-500℃; the tempering temperature T2 is 580℃-650℃. Based on the total weight of the forgings as 100%, the chemical composition of the forgings includes: 0.37%≤C≤0.44%, 0.17%≤Si≤0.37%, 0.5%≤Mn≤0.8%, P≤0.035%, S≤0.035%, 0.8%≤Cr≤1.1%, Ni≤0.3%, Cu≤0.25%, and the remaining components of the forgings are Fe and impurities.

2. The high-temperature deformation heat treatment process for forgings according to claim 1, characterized in that, The phase transition temperature AC3 = 903 - 233.7 W C +438.5W P +30.49W Si +37.92W v -34.43W Mn -23W Ni -200 (W) C -0.54 +0.06 W Ni (℃).

3. The high-temperature deformation heat treatment process for forgings according to claim 1, characterized in that, The cooling time in the precooling step is 20s-50s.

4. The high-temperature deformation heat treatment process for forgings according to claim 1, characterized in that, The pre-cooling step uses air cooling.

5. The high-temperature deformation heat treatment process for forgings according to claim 1, characterized in that, The cooling time in the quenching step is 10s-20s.

Images