A quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel

Abstract

The present invention belongs to the field of heat treatment of steel materials, and is particularly a quenching heat treatment method for improving the homogeneity of the structure and fatigue life of high carbon chromium bearing steel. The method is suitable for solving the problem that after quenching and tempering heat treatment of high carbon chromium bearing steel, carbides, grains and residual austenite are unevenly distributed, resulting in large deformation of the workpiece, poor hardness uniformity, and low or unstable toughness and fatigue life. The present invention reasonably designs the parameters of the quenching heating process according to the tissue state parameters before quenching, changes the stress release, carbide precipitation and austenitization driving force of the high carbon chromium bearing steel, and thus reduces the problem of uneven parameters of the quenched structure (such as: carbide, residual austenite size and distribution, etc.) on a microscopic scale, and then performs tempering treatment according to the original or appropriately adjusted low temperature tempering (and necessary deep cryogenic treatment) heat treatment process, thereby significantly improving the deformation, hardness uniformity, toughness and fatigue performance stability of the high carbon chromium bearing steel workpiece.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment of steel materials, in particular to a quenching heat treatment method for improving the homogeneity of high carbon chromium bearing steel structure and fatigue life. Background Art

[0002] High-end bearings are heavily dependent on imports, which has become one of the major bottlenecks restricting my country's high-end manufacturing industry. In recent years, with the improvement of my country's bearing steel smelting level, the number and size of inclusions in bearing steel have been greatly reduced, effectively improving the purity of bearing steel. On the basis of the significant improvement in the purity of bearing steel, the microstructure uniformity of bearing steel, including the uniformity of residual austenite and carbide distribution, has become increasingly important for its service performance.

[0003] High carbon chromium bearing steel is the type of bearing steel with the longest history of use and the most extensive application. The production process of bearing parts prepared by high carbon chromium bearing steel mainly includes hot rolling, spheroidizing annealing, cold rolling, quenching, deep cooling and low temperature tempering and other thermal processing processes. A large number of scholars have conducted extensive research on the influence of each of the above process parameters on the microstructure of high carbon bearing steel, and obtained the optimized process parameters and successfully applied them. For example, for the quenching process, considering the control of matrix solid solution carbon, carbides and residual austenite in the quenched structure of bearing steel, the quenching temperature is generally selected at about 840℃, the holding time is about 0.5-2h, and the quenching oil temperature is usually controlled at about 80℃; low-temperature tempering mainly selects reasonable tempering temperature and tempering time based on the hardness requirements of the bearing service conditions. Generally, the tempering temperature is between 150 and 250℃, and the tempering time is generally between 2 and 6 hours; and the deep cooling temperature is generally selected between -60℃ and -120℃ to minimize or eliminate the residual austenite in the quenched structure while ensuring that the workpiece is less deformed.

[0004] It is worth noting that previous research and applications have paid little attention to the impact of heating history on the microstructural evolution and performance of bearing steel, which has led to the uneven quality of high-carbon chromium bearings produced by different domestic companies or even by the same company in different batches. Recent research by the applicant shows that with the improvement of the smelting level of bearing steel (such as inclusions, macro-segregation control, etc.), the homogeneity of bearing steel at the microscopic scale (such as carbide and residual austenite size and distribution) has an important influence on its performance (such as hardness, toughness and fatigue life, etc.).

[0005] Generally speaking, the average carbon concentration of the matrix and the content of the second phase (carbide and retained austenite) in high carbon chromium bearing steel are mainly affected by the quenching temperature, while the distribution of carbon concentration and second phase in the matrix is ​​closely related to the processing history (such as spheroidized initial structure, hot and cold deformation, heating and cooling history, etc.). Among them, the quenching and heating history process has the most significant effect on the carbide dissolution rate, austenite nucleation and carbon element distribution behavior during the quenching process of high carbon chromium bearing steel. It will directly determine the uniformity of the matrix solid solution carbon and the second phase distribution in the quenched structure, and then affect the deformation, hardness, toughness and fatigue performance stability of the high carbon chromium bearing steel workpiece. Summary of the invention

[0006] The purpose of the present invention is to provide a quenching heat treatment method for improving the homogeneity of the structure and fatigue life of high carbon chromium bearing steel, which is suitable for solving the problems of workpiece deformation, uneven hardness, low or unstable toughness and fatigue life due to uneven distribution of carbides, grains and residual austenite after quenching and tempering heat treatment of high carbon chromium bearing steel.

[0007] The technical solution of the present invention:

[0008] A quenching heat treatment method for improving the homogeneity of high carbon chromium bearing steel structure and fatigue life, the method comprising the following steps:

[0009] (1) Spheroidizing or cold-processing high carbon chromium bearing steel workpiece, heating rate Heating to the insulation platform area oscillates or is at a uniform temperature, the oscillation interval temperature or insulation platform temperature T, time t1 and vibration amplitude ΔT, according to the phase change point A c1 The comprehensive parameters of the Brinell hardness value H and spheroidized structure rating C of the high carbon chromium bearing steel workpiece before quenching heat treatment are and Among them, D max and D min They are the maximum and minimum cross-sectional dimensions of the inner and outer rings of the bearing respectively; K1 and K2 are empirical values, ranging from 20 to 120°C·mm 2 / min and 1~3℃ / HB;

[0010] (2) After the high carbon chromium bearing steel workpiece is heated evenly or oscillated, the heating rate is increased. Raise the temperature to 60-100℃ above Ac1 for complete austenitization, and keep warm for a certain time. Calculation; K3 and K4 are empirical values, respectively 50 ~ 350 ℃ · mm 2 / min and 20~60min / mm; after the insulation is completed, the high carbon chromium bearing steel workpiece is immediately taken out of the furnace and put into the quenching medium. The interval time between taking out of the furnace and putting into the quenching medium is controlled at t3≤5~10min. The cooling method is carried out according to the original quenching process of high carbon chromium bearing steel, that is: continuous quenching is adopted, and the quenching oil temperature is 60~100℃; or, isothermal salt bath quenching is adopted, and the quenching temperature is 180~350℃.

[0011] The quenching heat treatment method for improving the homogeneity of the high carbon chromium bearing steel structure and the fatigue life is as follows: the high carbon chromium bearing steel alloy elements mainly include, by weight percentage: 0.8% ≤ C ≤ 1.2%, Mn ≤ 2.0%, Si ≤ 1.2%, 0.5% ≤ Cr ≤ 3%, Mo ≤ 0.5%, Ni ≤ 0.5%, the total mass fraction of the alloy elements does not exceed 5%, and the remainder is Fe.

[0012] The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel, the alloying elements of high carbon chromium bearing steel also include one or more of trace alloying elements rare earth (REs), V, B, and the mass fraction of the trace alloying elements is ≤0.1%.

[0013] The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel is aimed at the cross-sectional size variation D max ≥2D min For high carbon chromium bearing steel workpieces, the heating rates in the first and second stages of heating are carried out according to the formulas listed in V1 and V2; Or high carbon chromium bearing steel workpieces with equal cross-section, the heating rate should not exceed 20℃ / min while meeting the furnace temperature uniformity requirements.

[0014] The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel is as follows: before quenching heat treatment, the Brinell hardness value H of the high carbon chromium bearing steel workpiece meets the requirements of the national standard GB / T18254-2016, and the spheroidizing structure rating is performed according to JB / T1225-2014.

[0015] The quenching heat treatment method for improving the homogeneity of the structure and fatigue life of high carbon chromium bearing steel comprises step (1) setting a temperature equalization or oscillation step during the heating process according to the initial structure of the high carbon chromium bearing steel before quenching, the workpiece size and economic benefits; or, decomposing the oscillation step into more than two steps, and adjusting the oscillation range as needed.

[0016] The quenching heat treatment method for improving the homogeneity of the high carbon chromium bearing steel structure and the fatigue life, the carbide size and distribution after quenching are uniform, ensuring that every 100μm 2 The number of carbide particles with a diameter greater than 0.1 μm is greater than 50, that is, no obvious carbide-poor region appears.

[0017] The quenching heat treatment method for improving the homogeneity of the high carbon chromium bearing steel structure and fatigue life, the quenching structure obtained by this method is: carbide + martensite, bainite or mapeite composite structure + a small amount of residual austenite; according to the original conventional low-temperature tempering process of high carbon chromium bearing steel or adjustment, combined with deep cryogenic treatment when necessary, the hardness of the high carbon chromium bearing steel workpiece is controlled between 58HRC and 62.5HRC, and the residual austenite is controlled within 15vol.%.

[0018] The design concept of the present invention is:

[0019] In order to solve the problems of large quenching deformation and structural uniformity caused by different bearing sizes, uneven wall thickness and differences in initial quenching structures, the present invention reasonably designs the quenching heating and insulation process according to the cross-sectional size (diameter) of the workpiece and the initial structural state parameters before quenching, changes the driving force of stress release, carbide precipitation and austenitization of high carbon chromium bearing steel, thereby alleviating the problem of uneven parameters of quenched structural state (such as carbide, residual austenite size and distribution, etc.) on the micro scale, and then performs tempering treatment according to the original or appropriately adjusted low-temperature tempering (necessary deep cold treatment) heat treatment process, thereby significantly improving the deformation, hardness uniformity, toughness and fatigue performance stability of high carbon chromium bearing steel workpieces.

[0020] The advantages and beneficial effects of the present invention are as follows:

[0021] 1. The present invention, without changing the chemical composition of high-carbon chromium bearing steel, only changes the internal stress release, carbide precipitation and austenitization driving force in the bearing steel through reasonable design of heating and heat preservation, etc., to reduce the problem of uneven quenching structure parameters of bearing steel on a microscopic scale, and then performs low-temperature tempering treatment (deep cooling if necessary), which can reduce the problem of uneven quenching structure parameters of bearing steel on a microscopic scale, thereby solving the problems of large quenching deformation, poor hardness uniformity, low or unstable toughness and fatigue performance of high-carbon chromium bearing steel workpieces in actual production. It can be seen that the invention does not require large-scale transformation of existing bearing steel heat treatment equipment, and significantly improves the stability of the structure and performance of high-carbon chromium bearing steel without increasing or increasing costs.

[0022] 2. The present invention is a quenching heat treatment method that can solve the problems of large quenching deformation, poor hardness uniformity, low or unstable toughness and fatigue performance of high carbon chromium bearing steel workpieces in actual production by setting reasonable temperature uniformity steps or oscillation insulation in the quenching heating stage according to the workpiece size and initial organizational state, thereby improving the organizational homogeneity and fatigue life of high carbon chromium bearing steel. This method can be adapted to continuous quenching or isothermal quenching processes, and can be based on the characteristics of high carbon chromium bearing steel workpieces (such as workpiece shape, deformation, A c1and tissue state) to optimize the number of insulation steps and the width of the oscillation interval.

[0023] 3. The process of the present invention is simple, the operation is easy to implement, and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the quenching heat treatment process of the present invention.

[0025] Figure 2 These are SEM images of the structures of the sample in Example 1 after conventional heat treatment (a) and the process of the present invention (b).

[0026] Figure 3 EBSD images of the sample in Example 1 after conventional heat treatment (a) and the process of the present invention (b).

[0027] Figure 4 This is the grain corrosion metallographic structure of the sample in Example 2 after conventional heat treatment (a) and the process of the present invention (b).

[0028] Figure 5 These are SEM images of the sample in Example 3 after conventional heat treatment (a) and the process of the present invention (b). DETAILED DESCRIPTION

[0029] In order to well reflect that the process of the present invention significantly improves the homogeneity of the high carbon bearing steel structure and the fatigue life effect. In the subsequent specific implementation scheme, the present invention also lists the traditional heat treatment process to illustrate the superiority of the present invention, but the traditional heat treatment process does not mean that it is protected and restricted by the present invention. At the same time, in order to prove that the present invention has a wide range of applications and prospects, and considering the feasibility of actual operation, the present invention selects three high carbon chromium bearing steel workpieces in different processing states before quenching: one is a high-precision machine tool bearing inner and outer ring of model 7008 produced by a certain enterprise, the material is GCr15, the initial state of the ring before heat treatment is spheroidizing annealing + cold rolling expansion + turning, and the quenching method adopts continuous quenching; one is a high carbon chromium bearing inner and outer ring for locomotives, the material is GCr15SiMn, the process before heat treatment of the ring is high temperature forging + spheroidizing annealing + turning, and the quenching method adopts isothermal quenching; one is a high carbon chromium bearing steel for the main shaft bearing roller of the shield machine, the material is GCr18Mo, and the initial state of the roller before heat treatment is spheroidizing + turning.

[0030] Below, the present invention is further described in detail by examples:

[0031] Example 1

[0032] In this embodiment, the heat treatment process for improving the service life and stability of the bearing ring of a precision machine tool is as follows:

[0033] (1) The chemical composition analysis of the inner and outer rings of the 7008 precision machine tool bearing provided by a certain enterprise was carried out. The test results were 0.95C (weight percentage, the same below), 0.05Si, 1.45Cr, 0.18Mn, 0.07Ni, 0.006P, 0.002S, and the balance was Fe. The results meet the requirements of the relevant standards for the chemical composition of GCr15 steel and fall within the scope of application of the present invention. The phase transition point A c1 756℃;

[0034] (2) 500 sets of machine tool bearing inner and outer rings are evenly placed in a material frame and then placed in a vacuum heat treatment furnace for heat treatment. Figure 1 As shown, the furnace is heated to 735℃ with a step oscillation at 160℃ / h, with an oscillation amplitude of 30℃ for 2h, and then slowly heated to 840℃ at a heating rate of 80℃ / h, austenitized and kept for 0.5h, and oil quenched immediately after being taken out of the furnace. The quenching oil temperature is controlled at 60℃~90℃, and the oil quenching time is controlled at about 20min.

[0035] (3) After quenching, the inner and outer rings of the machine tool bearing are cleaned and blown dry, and then placed in a low temperature box for deep freezing treatment at -120°C and kept warm for 2.5 hours. Finally, the inner and outer rings of the machine tool bearing are taken out of the box and defrosted and cleaned;

[0036] (4) According to the environment in which the machine tool bearing is used, the hardness of the inner and outer rings of the machine tool bearing should be around 61.5HRC, and the residual austenite should be controlled within 5%. Therefore, the inner and outer rings of the machine tool bearing are heated to 180℃ at a rate of 100℃ / h, tempered and kept warm for 2.5h, and then taken out of the furnace and air-cooled.

[0037] (5) In order to compare with the heat treatment process of the present invention, another 500 sets of inner and outer rings of machine tool bearings of the same batch (same material, cold / hot processing process and model) were treated according to the traditional heat treatment process used by existing enterprises. The specific heat treatment process was 840℃×0.5h quenching +-120℃×2.5h deep cold treatment + 180℃×2.5h tempering treatment. The quenching and tempering heating rates were about 100-200℃ / h. The quenching and tempering cooling methods were the same as the process of the present invention.

[0038] (6) The deformation (including ovality and taper) of 500 sets of inner and outer rings of machine tool bearings after heat treatment by the process of the present invention and the traditional heat treatment process were statistically analyzed, and the results are shown in the following Table 1. It can be seen that the average deformation of the inner and outer rings of machine tool bearings after heat treatment by the process of the present invention is less than that by the traditional heat treatment process.

[0039] Table 1 Average deformation of high-precision machine tool bearing rings under the process of the present invention and the traditional process

[0040]

[0041] (7) After the conventional heat treatment process and the process of the present invention were randomly selected, the inner and outer rings of the machine tool bearings were tested for Rockwell hardness and Vickers hardness. The results show that the Rockwell hardness values ​​of the inner and outer rings of the machine tool bearings obtained by the two heat treatment processes are about 61.5HRC, while the Vickers hardness (HV 10 ) The average Vickers hardness of 120 points is 736 and 735 HV, which are not much different. However, the standard deviations of the Vickers hardness of the inner and outer rings of the machine tool bearings under the two processes are 61.6 and 46.3 HV, respectively, indicating that the micro-hardness uniformity of the samples under the process of the present invention is better. Further XRD and TEM analysis of the retained austenite in the organization found that although the retained austenite inside the inner and outer rings of the machine tool bearings under the two processes is controlled at about 5%, the retained austenite under the process of the present invention is more evenly dispersed, and no blocky retained austenite is present.

[0042] (8) Scanning electron microscope observation and analysis found that the uniformity of carbide distribution in the inner and outer rings of machine tool bearings produced by the process of the present invention is significantly higher than that of the conventional process (see Figure 2 ). That is, the mottled area (consisting of obvious carbide-poor area and carbide-rich area) commonly seen in the microstructure of the traditional process is significantly reduced; further EBSD analysis of the inner and outer ring structures of machine tool bearings after heat treatment by the traditional heat treatment process and the process of the present invention (see Figure 3 ), which shows that the distribution uniformity of carbides and retained austenite in the inner and outer rings of machine tool bearings in the process of the present invention is significantly higher than that in the traditional process.

[0043] (9) The machine tool bearing rings obtained by the two heat treatment processes were further ground into high-precision machine tool bearing rings, and finally the qualified machine tool bearing rings were assembled into P4-level high-precision machine tool bearings for bench testing. Preliminary results show that the grinding yield rate of machine tool bearing rings obtained by the process of the present invention is significantly higher than that obtained by the traditional process, and the service life of high-precision machine tool bearings obtained by the process of the present invention can reach more than twice that of high-precision machine tool bearings obtained by the traditional process.

[0044] Example 2

[0045] In this embodiment, the heat treatment process for improving the service life and stability of the high carbon chromium bearing ring for locomotive is as follows:

[0046] (1) The chemical composition of the high carbon chromium bearing ring for locomotives was analyzed, and the test results were 0.98C (weight percentage, the same below), 0.65Si, 1.53Cr, 1.2Mn, 0.25Ni, 0.05Mo, 0.007P, 0.003S, and the balance was Fe. The results meet the requirements of the relevant standards for the chemical composition of GCr15SiMn steel and fall within the scope of application of the present invention. The phase transition point A c1 748℃;

[0047] (2) Figure 1 As shown, according to the hardness of the workpiece, the degree of cold working deformation and the A of the bearing steel c1 Temperature, the ring is heated at a rate of 150℃ / h, heated to about 720℃ for oscillation insulation, the oscillation temperature range is controlled at ±16℃, the oscillation insulation time is 2h, then heated to 835℃ at 80℃ / h for 1h for austenitization treatment, and finally salt bath treatment is adopted, the salt bath temperature is controlled at about 270℃, and the salt bath treatment time is 1h, then Mapei composite structure + carbide can be obtained, and the hardness of the inner and outer rings is about 60.5HRC;

[0048] (3) In order to compare with the heat treatment process of the present invention, the same batch of rings were treated using a conventional isothermal quenching heat treatment process. The specific heat treatment process was 835°C × 1h austenitizing treatment + 270°C × 1h salt bath treatment, the quenching heating rate was about 150°C / h, and the quenching medium and holding temperature were the same as those of the process of the present invention.

[0049] (4) The rings after heat treatment by the conventional heat treatment quenching process and the quenching process of the present invention were randomly tested for Vickers hardness (HV 10 ) 120 points, the average Vickers hardness of the two groups of samples was measured to be 716 and 709 HV, which is not much different, but the standard deviations of the Vickers hardness of the two samples are 58.3 and 37.4 HV, respectively, indicating that the microhardness uniformity of the samples under the process of the present invention is better; the corrosion metallographic structure of the original austenite grains under the two processes is as follows Figure 4 As shown, it can be seen that the grain size of the bearing ring of the process of the present invention is more uniform and fine;

[0050] (5) Samples were cut from the bearing rings of the two heat treatment processes to process tensile, impact and ultrasonic tensile-compression fatigue samples, and the mechanical properties of the high carbon bearing steel were tested. The specific results are shown in Table 2. It can be seen that under the condition of equivalent bearing steel strength, the impact toughness and stability of the bearing steel are significantly improved under the process of the present invention, and the ultrasonic fatigue life is increased by more than 2 times.

[0051] Table 2: Performance comparison of GCr15SiMn steel using the process of the present invention and the traditional heat treatment process in the embodiment

[0052]

[0053] Example 3

[0054] In this embodiment, the heat treatment process for improving the hardness uniformity and wear resistance of the shield machine main bearing roller is as follows:

[0055] (1) The chemical composition of the steel used for the main shaft bearing roller of a shield machine provided by a certain enterprise was analyzed. The test results showed that the steel was 1.01C (weight percentage, the same below), 0.27Si, 1.76Cr, 0.56Mo, 0.65Mn, 0.07Ni, 0.006P, 0.002S, and the balance was Fe. The results met the requirements of the relevant standards for the chemical composition of GCr18Mo steel and fell within the scope of application of the present invention. The phase transition point A was measured. c1 is 762℃, and the initial hardness before heat treatment is 208HBS;

[0056] (2) 30 shield machine main shaft bearing rollers are evenly placed in a material frame and then placed in a roller hearth furnace for heat treatment. Figure 1 As shown, the steel is heated to 735℃ for step oscillation tempering at 160℃ / h, with the oscillation amplitude not exceeding 20℃ for 3h, and then slowly heated to 860℃ at a heating rate of 50℃ / h, austenitized and kept for 80min, and oil quenched immediately after being taken out of the furnace. The quenching oil temperature is controlled at 60℃~90℃, and the residence time in the quenching oil is controlled at about 20min.

[0057] (3) After quenching, the shield machine main shaft bearing roller is cleaned and blown dry, and then immediately placed in a tempering furnace for tempering. The specific tempering heat treatment process is 200°C × 2.5h tempering treatment, and the tempering heating rate is about 150-300°C / h.

[0058] (4) According to the environment in which the shield machine bearing is used, the surface hardness of the shield machine main shaft bearing roller should be around 62.5HRC, the retained austenite should be controlled within 10%, the core hardness should not be less than 58.5HRC, and the retained austenite content should be controlled within 10%. Therefore, the shield machine main shaft bearing roller is heated to 200℃ at a rate of 100℃ / h, tempered and kept warm for 2.5h, and then taken out of the furnace and air-cooled.

[0059] (5) In order to compare with the heat treatment process of the present invention, another 30 shield machine main shaft bearing rollers of the same batch (same material, cold / hot processing process and model) were treated according to the traditional heat treatment process used by existing enterprises. The specific heat treatment process was 860℃×0.5h quenching + 200℃×2.5h tempering treatment. The quenching and tempering heating rates were about 100-200℃ / h. The quenching and tempering cooling methods were the same as the process of the present invention.

[0060] (6) The mechanical properties (including hardness and impact toughness) of 30 shield machine main shaft bearing rollers after heat treatment by the process of the present invention and the traditional heat treatment process were statistically analyzed, and the results are shown in the following Table 3. It can be seen that the hardness and room temperature unnotched impact toughness and uniformity of the shield machine main shaft bearing rollers after heat treatment by the process of the present invention are better than those of the traditional heat treatment process.

[0061] Table 3 Comparison of mechanical properties of shield machine main shaft bearing rollers under the process of the present invention and the traditional process

[0062]

[0063] like Figure 5 As shown, from the SEM images of the samples after conventional heat treatment (a) and the process of the present invention (b) in Example 3, it can be seen that the uniformity of carbide distribution in the main shaft bearing roller of the shield machine by the process of the present invention is significantly higher than that by the conventional process. That is, the mottled area (consisting of obvious carbide-poor areas and carbide-rich areas) commonly seen in the microstructure of the conventional process is significantly reduced.

[0064] The results of the above embodiments show that the present invention develops a quenching heat treatment process for high carbon chromium bearing steel according to the shape and initial state of the workpiece, which solves the problem that the uneven distribution of carbides, grains and residual austenite in the high carbon chromium bearing steel leads to large deformation of the workpiece, poor hardness uniformity, low or unstable toughness and fatigue life, and has important practical significance; while the quenching process of the present invention ensures that the hardness of the high carbon chromium bearing steel is equivalent, the quenching deformation of the workpiece is significantly reduced, the notch-free room temperature impact toughness can be increased by 30%, and the ultrasonic fatigue life can be increased by more than 2 times.

Claims

1. A quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel, characterized in that: The method comprises the following steps: (1) Spheroidizing or cold-processing high carbon chromium bearing steel workpiece, heating rate Heating to the insulation platform area oscillates or is at a uniform temperature, the oscillation interval temperature or insulation platform temperature T, time t1 and vibration amplitude ΔT, according to the phase change point A c1 The comprehensive parameters of the Brinell hardness value H and spheroidization structure rating C of the high carbon chromium bearing steel workpiece before quenching heat treatment are and Among them, D max and D min They are the maximum and minimum cross-sectional dimensions of the inner and outer rings of the bearing respectively; K1 and K2 are empirical values, ranging from 20 to 120°C·mm 2 / min and 1~3℃ / HB; (2) After the high carbon chromium bearing steel workpiece is heated evenly or oscillated, the heating rate is increased. Raise the temperature to 60-100℃ above Ac1 for complete austenitization, and keep warm for a certain time. Calculation; K3 and K4 are empirical values, respectively 50 ~ 350 ℃ · mm 2 / min and 20~60min / mm; after the insulation is completed, the high carbon chromium bearing steel workpiece is immediately taken out of the furnace and put into the quenching medium. The interval time between taking out of the furnace and putting into the quenching medium is controlled at t3≤5~10min. The cooling method is carried out according to the original quenching process of high carbon chromium bearing steel, that is: continuous quenching is adopted, and the quenching oil temperature is 60~100℃; or, isothermal salt bath quenching is adopted, and the quenching temperature is 180~350℃.

2. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: Measured by weight percentage, the alloying elements of high carbon chromium bearing steel mainly include: 0.8%≤C≤1.2%, Mn≤2.0%, Si≤1.2%, 0.5%≤Cr≤3%, Mo≤0.5%, Ni≤0.5%, the total mass fraction of the alloying elements does not exceed 5%, and the balance is Fe.

3. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 2, characterized in that: The alloying elements of the high carbon chromium bearing steel also include one or more of trace alloying elements rare earth (REs), V, and B, and the mass fraction of the trace alloying elements is ≤0.1%.

4. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: For cross-sectional size D max ≥2D min For high carbon chromium bearing steel workpieces, the heating rates in the first and second stages of heating are carried out according to the formulas listed in V1 and V2; Or high carbon chromium bearing steel workpieces with equal cross-section, the heating rate should not exceed 20℃ / min while meeting the furnace temperature uniformity requirements.

5. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: Before quenching heat treatment, the Brinell hardness value H of the high carbon chromium bearing steel workpiece meets the requirements of the national standard GB / T18254-2016, and the spheroidizing structure rating is carried out according to JB / T1225-2014.

6. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: During the heating process of step (1), a uniform temperature or oscillation step is set according to the initial structure of the high carbon chromium bearing steel before quenching, the size of the workpiece and for economic benefits; alternatively, the oscillation step is decomposed into two or more steps, and the oscillation range is adjusted as needed.

7. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: The carbide size and distribution after quenching are uniform, ensuring that every 100μm 2 The number of carbide particles with a diameter greater than 0.1 μm is greater than 50, that is, no obvious carbide-poor region appears.

8. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 1, characterized in that: The quenched structure obtained by the method is: carbide + martensite, bainite or mapeite composite structure + a small amount of residual austenite; according to the original conventional low-temperature tempering process of high-carbon chromium bearing steel or adjusted.

9. The quenching heat treatment method for improving the homogeneity and fatigue life of high carbon chromium bearing steel according to claim 8, characterized in that: Combined with cryogenic treatment, the hardness of the high carbon chromium bearing steel workpiece is controlled between 58HRC and 62.5HRC, and the retained austenite is controlled within 15vol.%.

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