A heat treatment method for high-toughness high-carbon chromium bearings

Abstract

The present invention discloses a heat treatment method for a high-toughness high-carbon chromium bearing, and belongs to the technical field of bearing heat treatment. The present invention sequentially performs solid solution pretreatment, spheroidizing annealing, austenitizing and isothermal quenching treatment on the high-carbon chromium bearing; the steps of the isothermal quenching treatment are: the austenitized high-carbon chromium bearing is rapidly cooled to a temperature of Ms-(10-40)°C and kept warm for 10-20 minutes, then placed at a temperature of Ms+(30-50)°C and kept warm for 50-70 minutes, and then cooled to Ms+(5-10)°C and kept warm for 180-220 minutes. The metallographic structure obtained by the above-mentioned heat treatment method has good uniformity, and the high-carbon chromium bearing after heat treatment has greatly improved toughness while maintaining high hardness, and has high strength and good wear resistance; at the same time, the heat treatment process is relatively simple, with low energy consumption and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of bearing heat treatment, and in particular to a heat treatment method for a high-toughness high-carbon chromium bearing. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] As the world's first generation of bearing steel, high carbon chromium bearing steel has been used to this day because of its high strength, hardness and excellent wear resistance. However, with the continuous development of industrial technology and the increasing application demand, traditional martensitic bearings have gradually exposed problems such as short service life and frequent accidents when dealing with harsh working conditions such as heavy loads, complex alternating stresses and large impact loads. Against this background, the emergence of bainitic bearings has brought new hope to the bearing industry. Compared with martensitic bearings, bainitic bearings show higher toughness and wear resistance while maintaining high hardness, enabling them to maintain stable performance under complex and changeable working conditions. For this reason, more and more high-end bearing products are beginning to use bainitic bearing steel to meet the market's urgent demand for high-quality, high-performance bearings.

[0004] Patent CN 112941274 B (grant date: 2023.02.28) discloses a method for improving the strength and toughness of high-carbon chromium steel and its application, which is to heat and forge the high-carbon chromium steel to be treated, and then perform isothermal salt bath and isothermal post-quenching in sequence to obtain a mixed structure mainly composed of bainite and martensite. It is claimed that the mixed structure is evenly distributed, dense and fine, and significantly improves toughness while maintaining high strength. Among them, the heating and forging treatment includes at least three different stages of forging process: high temperature forging, room temperature pre-deformation, and medium temperature forging. However, the preparation process of this patent is complicated and requires multiple forgings, which will consume a lot of energy, increase production costs, and cause greater environmental pollution.

[0005] Patent CN 116555530 A (publication date: 2023.08.08) discloses a heat treatment method for high carbon chromium bearing steel, which austenitizes the high carbon chromium bearing steel after spheroidizing annealing, and then performs pre-salt bath quenching, and then performs the first stage of isothermal salt bath quenching of the high carbon chromium bearing steel at a first temperature, and then performs the second stage of isothermal salt bath quenching at a second temperature, and then performs air cooling and tempering. This patent can obtain high carbon chromium bearing steel with a bainite content of 55-58%, and has excellent wear resistance. However, it can be seen from the patent that different heat treatment processes are used to adjust the metallographic structure ratio of each high carbon chromium bearing steel to be consistent, and the performance of the bearing steel will still show large differences; at the same time, the patent does not disclose the toughness and hardness data of the resulting bearing steel, and it is impossible to know how its heat treatment process affects the toughness and hardness.

[0006] Therefore, how to adopt a suitable heat treatment process to obtain bainitic high-carbon chromium bearings with high strength, high toughness and high hardness is an urgent problem to be solved. Summary of the invention

[0007] In view of this, the present invention provides a high-toughness high-carbon chromium bearing heat treatment method, which can obtain a high-carbon chromium bearing with a bainite content of more than 50%, which has high strength, high toughness, high hardness and high wear resistance, and has good structural uniformity and good comprehensive performance.

[0008] The present invention provides a high-toughness high-carbon chromium bearing heat treatment method, comprising the following steps:

[0009] The high carbon chromium bearing is sequentially subjected to solution pretreatment, spheroidizing annealing, austenitizing and isothermal quenching treatment; the isothermal quenching treatment comprises the steps of rapidly cooling the austenitized high carbon chromium bearing to a temperature of Ms-(10-40)°C and keeping the temperature for 10-20 minutes, then keeping the temperature at Ms+(30-50)°C and keeping the temperature for 50-70 minutes, and then cooling the bearing to Ms+(5-10)°C and keeping the temperature for 180-220 minutes.

[0010] Preferably, the step of the solid solution pretreatment is: heating the high carbon chromium bearing to 1000-1100° C. at a heating rate of 20-30° C. / min.

[0011] Preferably, the solution pretreatment holding time is 20 to 40 minutes.

[0012] Preferably, after the solution pretreatment step, quenching is performed by oil cooling.

[0013] Preferably, the spheroidizing annealing is performed by gradient cooling annealing.

[0014] Furthermore, the spheroidizing annealing step is: heating the high carbon chromium bearing after solution pretreatment to 760-790°C and keeping it warm for 20-40 minutes; then cooling it to 710-730°C and keeping it warm for 20-40 minutes; then cooling it to 640-660°C and keeping it warm for 20-40 minutes.

[0015] Furthermore, the heating rate of the spheroidizing annealing is 20-30°C / min, and the cooling rate is 20-40°C / h.

[0016] Preferably, after the spheroidizing annealing step, air cooling is performed to 350-550°C.

[0017] Preferably, the austenitizing step is: heating to 810-890° C. at a heating rate of 5-15° C. / min, and keeping the temperature for 50-70 minutes.

[0018] Preferably, the austempering step is performed in a nitrate bath.

[0019] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0020] (1) The present invention sequentially performs solid solution pretreatment, spheroidizing annealing, austenitizing and isothermal quenching treatment on the high carbon chromium bearing, so that the metallographic structure after heat treatment has good uniformity, and the high carbon chromium bearing after heat treatment has greatly improved toughness while maintaining high hardness, and has high strength and good wear resistance;

[0021] (2) The heat treatment process of the present invention is relatively simple, does not require multiple forging, and does not require tempering treatment, has low energy consumption and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a SEM picture of the sample after spheroidizing annealing in Example 1 of the present invention;

[0024] Figure 2 This is a SEM picture of the sample after spheroidizing annealing in Comparative Example 1 of the present invention;

[0025] Figure 3 is a metallographic structure diagram of the GCr15 bearing after heat treatment in Example 1 of the present invention;

[0026] Figure 4It is the metallographic structure diagram of the GCr15 bearing after the heat treatment of comparative example 3 of the present invention. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0028] The present invention provides a high-toughness high-carbon chromium bearing heat treatment method, comprising the following steps:

[0029] The high carbon chromium bearing is sequentially subjected to solution pretreatment, spheroidizing annealing, austenitizing and isothermal quenching treatment; the isothermal quenching treatment comprises the steps of rapidly cooling the austenitized high carbon chromium bearing to a temperature of Ms-(10-40)°C and keeping the temperature for 10-20 minutes, then keeping the temperature at Ms+(30-50)°C and keeping the temperature for 50-70 minutes, and then cooling the bearing to Ms+(5-10)°C and keeping the temperature for 180-220 minutes.

[0030] In the present invention, Ms is the temperature at which the high carbon chromium bearing starts to transform from austenite to martensite (martensite transformation start temperature).

[0031] The present invention first performs a solid solution pretreatment, heats the material to the solid solution temperature, dissolves the solute atoms into the matrix, and forms a uniform solid solution structure; then performs a spheroidizing annealing, heats the material to the spheroidizing annealing temperature, and then redistributes the solute atoms in the solid solution by cooling to form a spheroidal grain structure. The uniformity of carbides and spheroidization is ensured by first performing a solid solution pretreatment and then a spheroidizing annealing treatment, and a uniform solid solution structure and a spheroidal grain structure can be obtained, thereby improving the toughness, plasticity, and fatigue life of the material. In addition, the solid solution pretreatment can form a solid solution inside the crystal, improve the corrosion resistance and fatigue resistance of the material; the spheroidizing annealing can eliminate stress and defects, and improve the processing performance and deformation ability of the material.

[0032] After fully austenitizing, the present invention first cools to 10-40°C below the martensite transformation starting temperature (Ms point) and keeps warm to obtain a certain amount of lath martensite; then keeps warm in a salt bath at 30-50°C above the Ms point to quickly obtain a certain amount of lower bainite; then keeps warm at 5-10°C above the Ms point for a sufficient time to obtain a refined bainite structure, and the effect of this step is equivalent to tempering in traditional heat treatment, so there is no need to perform the tempering step. The metallographic structure obtained by the final heat treatment contains lath martensite, nano-bainite, a small amount of undissolved carbide and residual austenite, and the content of nano-bainite is between 50% and 60%. The high-carbon chromium bearing after heat treatment has both high toughness and high hardness, high strength and good wear resistance, is not easy to crack, break or deform during the application process, and has good application stability.

[0033] The steps of the solid solution pretreatment of the present invention are: heating the high carbon chromium bearing to 1000-1100° C. at a heating rate of 20-30° C. / min; and holding time of the solid solution pretreatment is 20-40 minutes.

[0034] The present invention performs quenching by oil cooling after the solution pretreatment step, so that the high-carbon chromium bearing is quickly cooled to room temperature and the carbon reaches a supersaturated state, which is convenient for precipitation of strengthening phases such as carbides with fine particles and uniform distribution during subsequent treatment. At the same time, the stress generated by cold and hot processing can be eliminated, which is convenient for alloy recrystallization.

[0035] The spheroidizing annealing of the present invention adopts a gradient cooling annealing method, and the gradient cooling can further ensure that the solute atoms in the solid solution are evenly distributed and form a spherical grain structure. The preferred spheroidizing annealing steps of the present invention are: heating the high carbon chromium bearing after solid solution pretreatment to 760-790°C and keeping it warm for 20 to 40 minutes; then cooling to 710 to 730°C and keeping it warm for 20 to 40 minutes; then cooling to 640 to 660°C and keeping it warm for 20 to 40 minutes. At this time, the carbide is fully spheroidized, and the organization is prepared for subsequent heat treatment. In the present invention, the heating rate when heating to the spheroidizing annealing temperature is 20 to 30°C / min, and the cooling rates of the two coolings are both 20 to 40°C / h.

[0036] After the spheroidizing annealing step, the present invention air cools to 350-550°C, and then fully utilizes the residual heat of the spheroidizing annealing treatment to perform austenitization. The austenitization step is specifically: heating to 810-890°C at a heating rate of 5-15°C / min, and keeping the temperature for 50-70min. Under the above conditions, sufficient austenitization can be ensured.

[0037] The isothermal quenching treatment step of the present invention is carried out in a nitrate bath. During the isothermal quenching treatment process, the nitrate bath is continuously stirred to ensure the uniformity of quenching.

[0038] In the present invention, the raw material for making the high carbon chromium bearing can be selected from GCr15 bearing steel, GCr15SiMn bearing steel, GCr9 bearing steel and the like.

[0039] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0040] Example 1

[0041] This embodiment provides a heat treatment method for a GCr15 bearing, whose Ms point is 210°C.

[0042] (1) Solution pretreatment: Prepare the GCr15 bearing specimens after forging and turning. Heat the specimens to 1050°C at a rate of 30°C / min in a heat treatment furnace and keep them at that temperature for 30 min. After the end of the heat preservation, take them out and immediately cool them to room temperature with oil.

[0043] (2) Spheroidizing annealing: Place the GCr15 bearing after solution pretreatment in a heat treatment furnace, first heat it to 760°C at a rate of 30°C / min, keep it at that temperature for 30 minutes, then cool it to 720°C at a rate of 30°C / h, keep it at that temperature for 30 minutes, then cool it to 650°C at a rate of 30°C / h again, keep it at that temperature for 30 minutes, and then take it out and air cool it to 500°C after the end of the heat preservation.

[0044] (3) Austenitization: The GCr15 bearing cooled to 500°C was heated to 860°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0045] (4) Isothermal quenching treatment: After the insulation is completed, it is immediately transferred to a 180°C salt bath furnace for insulation for 10 minutes. After the insulation is completed, it is immediately transferred to a 250°C salt bath furnace for insulation for 60 minutes. Then it is immediately transferred to a 215°C salt bath furnace for insulation for 200 minutes.

[0046] Example 2

[0047] This embodiment provides a heat treatment method for a GCr15 bearing, whose Ms point is 210°C.

[0048] (1) Solution pretreatment: Prepare the GCr15 bearing specimens after forging and turning. Heat the specimens to 1100°C at a rate of 25°C / min in a heat treatment furnace and keep them at that temperature for 30 min. After the end of the heat preservation, take them out and immediately cool them to room temperature with oil.

[0049] (2) Spheroidizing annealing: Place the GCr15 bearing after solution pretreatment in a heat treatment furnace, first heat it to 780℃ at a rate of 25℃ / min, keep it at that temperature for 30min, then cool it to 730℃ at a rate of 35℃ / h, keep it at that temperature for 30min, then cool it to 660℃ at a rate of 35℃ / h, keep it at that temperature for 30min, and then take it out and air cool it to 400℃.

[0050] (3) Austenitization: The GCr15 bearing cooled to 400°C was heated to 830°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0051] (4) Isothermal quenching treatment: After the insulation is completed, it is immediately transferred to a 180°C salt bath furnace for insulation for 10 minutes. After the insulation is completed, it is immediately transferred to a 250°C salt bath furnace for insulation for 60 minutes. Then it is immediately transferred to a 215°C salt bath furnace for insulation for 200 minutes.

[0052] Comparative Example 1

[0053] Compared with Example 1, the difference is that spheroidizing annealing is performed first, and then solid solution pretreatment is performed. The specific steps are as follows:

[0054] (1) Spheroidizing annealing: Prepare the GCr15 bearing specimens that have been forged and machined. Place the specimens in a heat treatment furnace, heat them to 760°C at a rate of 30°C / min, keep them at that temperature for 30 min, cool them to 720°C at a rate of 30°C / h, keep them at that temperature for 30 min, cool them to 650°C at a rate of 30°C / h, keep them at that temperature for 30 min, and take them out and air cool them to room temperature after the end of the heat preservation.

[0055] (2) Solution pretreatment: After spheroidizing annealing, the GCr15 bearing is heated to 1050℃ at a rate of 30℃ / min in a heat treatment furnace and kept at this temperature for 30min. After the end of the heat preservation, it is taken out and immediately oil-cooled to room temperature.

[0056] (3) Austenitization: The room temperature GCr15 bearing was heated to 860°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0057] (4) Isothermal quenching treatment: After the insulation is completed, it is immediately transferred to a 180°C salt bath furnace for insulation for 10 minutes. After the insulation is completed, it is immediately transferred to a 250°C salt bath furnace for insulation for 60 minutes. Then it is immediately transferred to a 215°C salt bath furnace for insulation for 200 minutes.

[0058] Comparative Example 2

[0059] Compared with Example 1, this comparative example does not perform solid solution pretreatment, but directly performs spheroidizing annealing, austenitizing and isothermal quenching treatment; the specific steps are as follows:

[0060] (1) Spheroidizing annealing: Place the GCr15 bearing sample after forging and turning in a heat treatment furnace, first heat it to 760℃ at a rate of 30℃ / min, keep it at that temperature for 30min, then cool it to 720℃ at a rate of 30℃ / h, keep it at that temperature for 30min, then cool it to 650℃ at a rate of 30℃ / h, keep it at that temperature for 30min, and then take it out and air cool it to 500℃.

[0061] (2) Austenitization: The GCr15 bearing cooled to 500°C was heated to 860°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0062] (3) Isothermal quenching treatment: After the insulation is completed, it is immediately transferred to a 180°C salt bath furnace for insulation for 10 minutes. After the insulation is completed, it is immediately transferred to a 250°C salt bath furnace for insulation for 60 minutes. Then it is immediately transferred to a 215°C salt bath furnace for insulation for 200 minutes.

[0063] Comparative Example 3

[0064] This comparative example adopts conventional isothermal quenching process + tempering process, and the specific steps are as follows:

[0065] (1) Solution pretreatment: Prepare the GCr15 bearing specimens after forging and turning. Heat the specimens to 1050°C at a rate of 30°C / min in a heat treatment furnace and keep them at that temperature for 30 min. After the end of the heat preservation, take them out and immediately cool them to room temperature with oil.

[0066] (2) Spheroidizing annealing: Place the GCr15 bearing after solution pretreatment in a heat treatment furnace, first heat it to 760°C at a rate of 30°C / min, keep it at that temperature for 30 minutes, then cool it to 720°C at a rate of 30°C / h, keep it at that temperature for 30 minutes, then cool it to 650°C at a rate of 30°C / h again, keep it at that temperature for 30 minutes, and then take it out and air cool it to 500°C after the end of the heat preservation.

[0067] (3) Austenitization: The GCr15 bearing cooled to 500°C was heated to 860°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0068] (4) Conventional isothermal quenching treatment: After the insulation is completed, it is immediately transferred to a 250°C salt bath furnace for insulation for 120 minutes, and then air-cooled to room temperature.

[0069] (5) Tempering: Heat to 210°C at a rate of 10°C / min, keep at this temperature for 1 h, and then air cool to room temperature.

[0070] Comparative Example 4

[0071] This comparative example adopts a conventional martensitic quenching heat treatment process, and the specific steps are as follows:

[0072] (1) Solution pretreatment: Prepare the GCr15 bearing specimens after forging and turning. Heat the specimens to 1050°C at a rate of 30°C / min in a heat treatment furnace and keep them at that temperature for 30 min. After the end of the heat preservation, take them out and immediately cool them to room temperature with oil.

[0073] (2) Spheroidizing annealing: Place the GCr15 bearing after solution pretreatment in a heat treatment furnace, first heat it to 760°C at a rate of 30°C / min, keep it at that temperature for 30 minutes, then cool it to 720°C at a rate of 30°C / h, keep it at that temperature for 30 minutes, then cool it to 650°C at a rate of 30°C / h again, keep it at that temperature for 30 minutes, and then take it out and air cool it to 500°C after the end of the heat preservation.

[0074] (3) Austenitization: The GCr15 bearing cooled to 500°C was heated to 860°C at a rate of 10°C / min and kept at this temperature for 60 min.

[0075] (4) Conventional martensitic quenching treatment: After the insulation is completed, it is immediately placed in the quenching oil tank and quenched to room temperature.

[0076] (5) Tempering: Heat to 210°C at a rate of 10°C / min, keep at this temperature for 1 h, and then air cool to room temperature.

[0077] Test example

[0078] 1. SEM determination:

[0079] The samples after spheroidizing annealing in Example 1 and Comparative Example 1 were measured by SEM, and the results were as follows: Figure 1 (Example 1) and Figure 2 As shown in (Comparative Example 1), it can be seen that the solid solution pretreatment is performed first and then the spheroidization annealing treatment is performed, the spheroidization is more uniform and the solid solution effect is better.

[0080] 2. Determination of the content of each component phase

[0081] The metallographic structure of the GCr15 bearings after heat treatment in Examples 1 to 2 and Comparative Examples 1 to 4 was measured, and the results are shown in Table 1.

[0082] Table 1 Metallographic structure content of GCr15 bearing after heat treatment of Examples 1-2 and Comparative Examples 1-4

[0083] Example / Comparative Example Martensite content (%) Bainite content (%) Other phase content (%) Example 1 34 55 11 Example 2 35 50 15 Comparative Example 1 38 44 18 Comparative Example 2 40 34 26 Comparative Example 3 42 36 22 Comparative Example 4 84 0 16

[0084] The metallographic structures of Example 1 and Comparative Example 3 are as follows: Figure 3 (Example 1) and Figure 4 (Comparative Example 3) As shown in FIG. 1 , it can be seen that the isothermal quenching process has a greater impact on the metallographic structure, and a suitable quenching process can enable the bearing to obtain a more excellent structure ratio.

[0085] 3. Mechanical properties determination

[0086] The hardness of the GCr15 bearings after heat treatment of Examples 1 to 2 and Comparative Examples 1 to 4 was measured using a Rockwell hardness tester. The impact toughness of the samples was tested using a pendulum impact tester. The room temperature tensile strength and yield strength of the samples were tested using a universal testing machine. The mechanical properties test results are shown in Table 2.

[0087] Table 2 Mechanical properties test results

[0088]

[0089] By comparing the mechanical properties of Examples 1 to 2 with Comparative Examples 1 to 3, it can be clearly observed that the austempering process has a significant effect on the mechanical properties of the bearings. The bearings in the examples have shown higher mechanical properties after optimized austempering. At the same time, compared with Comparative Example 4, the bearings treated with a reasonable austempering process have achieved varying degrees of improvement in mechanical properties such as toughness. This result fully demonstrates the importance of a reasonable heat treatment process for improving the mechanical properties of bearings.

[0090] 4. Friction and wear test

[0091] Friction and wear tests were performed on the GCr15 bearings after heat treatment in Example 1 and Comparative Example 3, and the GCr15 bearings in Comparative Example 4. The test load was 100N, the frequency was 4Hz, the reciprocating stroke was 4.5mm, and the time was 30min. The bearings were cleaned and weighed before and after friction and wear, and then the wear rate was calculated. The wear rate results are shown in Table 3. It can be seen that the wear resistance of the bearing after heat treatment in Example 1 is the best.

[0092] Table 3 Wear rate measurement results

[0093]

[0094]

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-toughness high-carbon chromium bearing heat treatment method, characterized in that: The steps include: The high carbon chromium bearing is sequentially subjected to solution pretreatment, spheroidizing annealing, austenitizing and isothermal quenching treatment; the isothermal quenching treatment comprises the steps of rapidly cooling the austenitized high carbon chromium bearing to a temperature of Ms-(10-40)°C and keeping the temperature for 10-20 minutes, then keeping the temperature at Ms+(30-50)°C and keeping the temperature for 50-70 minutes, and then cooling the bearing to Ms+(5-10)°C and keeping the temperature for 180-220 minutes; The spheroidizing annealing adopts a gradient cooling annealing method; the steps of the spheroidizing annealing are: heating the high carbon chromium bearing after solid solution pretreatment to 760-790°C and keeping it warm for 20-40 minutes; then cooling it to 710-730°C and keeping it warm for 20-40 minutes; then cooling it to 640-660°C and keeping it warm for 20-40 minutes; after the spheroidizing annealing step, air cooling it to 350-550°C, and then using the residual heat of the spheroidizing annealing treatment to perform austenitizing treatment.

2. The high-toughness high-carbon chromium bearing heat treatment method according to claim 1, characterized in that: The step of the solid solution pretreatment is: heating the high carbon chromium bearing to 1000-1100° C. at a heating rate of 20-30° C. / min.

3. The high-toughness high-carbon chromium bearing heat treatment method according to claim 2, characterized in that: The solution pretreatment heat preservation time is 20 to 40 minutes.

4. The high-toughness high-carbon chromium bearing heat treatment method according to claim 1, characterized in that: After the solution pretreatment step, quenching is performed by oil cooling.

5. The high-toughness high-carbon chromium bearing heat treatment method according to claim 1, characterized in that: The heating rate of the spheroidizing annealing is 20-30°C / min, and the cooling rate is 20-40°C / h.

6. The high-toughness high-carbon chromium bearing heat treatment method according to claim 1, characterized in that: The austenitizing step is: heating to 810-890° C. at a heating rate of 5-15° C. / min, and keeping the temperature for 50-70 minutes.

7. The high-toughness high-carbon chromium bearing heat treatment method according to claim 1, characterized in that: The austempering step is performed in a nitrate bath.

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