Preparation process of bearing ring, bearing ring and generator

Abstract

The invention discloses a preparation process of a bearing ring, the bearing ring and a generator, and belongs to the technical field of hot working of parts. The preparation process comprises a thermal deformation procedure, and the thermal deformation procedure comprises the steps of S1, upsetting, S2, punching, S3, leveling, S4, pre-ring rolling, S5, furnace returning and heating and S6, ring rolling. The step S6 comprises the following steps that S6.1, high-temperature ring rolling is conducted, specifically, the machined part is subjected to ring rolling after being discharged out of the furnace in the step S5, and when ring rolling is started, the temperature of the machined part is 1000-1100 DEG C; and S6.2, low-temperature ring rolling is conducted, the machined part is subjected to ring rolling after high-temperature ring rolling is conducted, and when ring rolling is started, the temperature of the machined part is 900-950 DEG C. The strength, toughness and corrosion resistance of the bearing ring product can be synchronously improved, and the service life of the bearing ring product is further prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal processing of parts, and particularly relates to a preparation process of a bearing ring with refined austenite grains, a bearing ring prepared by the preparation process, and a generator using the bearing ring. Background Art

[0002] As a core component of mechanical equipment, the performance and service life of rolling bearings are directly related to the operational reliability, precision retention, and maintenance costs of the entire equipment. Bearing rings, as the primary load-bearing component of the bearing, are subject to complex alternating contact stresses. Their inherent quality, particularly their microstructure, is a key factor in determining bearing fatigue life. In modern industrial fields that pursue high precision, long life, and high reliability, improving the microstructural uniformity and grain refinement of bearing rings is of paramount engineering value.

[0003] The current manufacturing process for mass-produced bearing rings typically includes a series of hot deformation steps. These steps aim to efficiently transform raw bar or tube stock into ring forgings that approach the final shape, laying the foundation for subsequent finishing. The core process generally includes the following steps: Initially, the raw material is upset: upsetting the ends to increase the diameter, reduce the height, and initially compact the structure; followed by punching: removing material from the center to form the ring blank; then, flattening: correcting the ring blank's shape and improving dimensional and thickness uniformity; then, pre-rolling: preliminary ring rolling to reduce the wall thickness and expand the diameter, resulting in a pre-expanded ring close to the target size; then, the pre-expanded ring is returned to the furnace for heating to provide sufficient heat for the final, precise deformation; and finally, rolling: the finishing stage of ring rolling, achieving precise dimensions and high shape accuracy. This hot deformation process has become widely adopted in the pursuit of efficient and cost-effective mass production.

[0004] However, rolling belongs to the machinery industry, and the focus of production at home and abroad is on forming issues, including defects such as size, roundness, and folding. Little attention is paid to the refinement of austenite grains during hot rolling. Although the above process route is mature and stable, in actual production, some batches of bearing rings produced by this process often fail to meet the design expectations or ideal levels in terms of contact fatigue life and overall durability during service, resulting in a prominent problem of unsatisfactory service life. Through a large number of failure analyses and microstructural inspections, the root cause of this problem has gradually become clearer, pointing to internal microstructural defects in the ring material: ① Insufficient austenite grain coarsening and refinement: The core defect manifests itself as insufficient refinement of high-temperature austenite grains during thermal deformation and subsequent heat treatment, resulting in coarse austenite grains remaining in the final product or severely insufficient grain refinement. Coarse austenite grains often genetically transform into coarse quenched martensite upon cooling, significantly weakening the material's strength, toughness, and fatigue resistance.

[0005] ② Mixed-crystal defects: In some cases, the ferrule material not only suffers from coarse grains but also exhibits mixed-crystal phenomena. This manifests as the irregular coexistence of fine grains and unusually coarse grains within the same microscopic region. This dramatic fluctuation in grain size creates significant structural inhomogeneity. These inhomogeneities create stress concentration points, which become the primary source of fatigue crack initiation, significantly accelerating premature failure of the material.

[0006] In summary, existing thermal deformation processes often result in suboptimal austenite grain refinement and frequent mixed-grain defects in bearing ring materials, which has become a bottleneck restricting improvements in service performance and fatigue life. This urgently requires innovative optimization of existing processes or the introduction of new control methods. Summary of the Invention

[0007] The invention provides a preparation process of a bearing ring, the bearing ring and a generator.

[0008] The inventors have concluded through research and analysis of the prior art that: During the preparation of bearing rings, the reheating process will inevitably eliminate the effect of the previous thermal deformation on the refinement of austenite grains. This is because the reheating temperature is high (e.g., over 930°C) and the holding time is long, which causes the austenite grains to merge and grow rapidly through atomic diffusion. This makes the final rolling forming stage the decisive step in the refinement of the austenite grains of the entire bearing ring. The conventional rolling step is a one-time rolling process, that is, the steel is directly deformed after being returned to the furnace for heating. This operation has two hazards for the refinement of austenite grains: ① As mentioned above, high temperature is not conducive to the refinement of austenite grains. The temperature at the beginning of rolling (around 1100°C) and the temperature at the end of rolling (above 900°C) are both high, which hinders the refinement of austenite grains. ② After rolling, under the higher final rolling temperature environment, the size of the austenite grains will grow significantly for a second time, further coarsening the austenite grain size of the bearing ring.

[0009] The technical solution of the present invention is formed based on the above-mentioned understanding and is dedicated to solving the problem of poor service life of bearing ring products.

[0010] The specific technical solution is described below: A preparation process for a bearing ring includes a thermal deformation process, wherein the thermal deformation process includes the following steps: S1: upsetting, S2: punching, S3: leveling, S4: pre-rolling, S5: reheating, S6: rolling; The above step S6 includes the following steps: S6.1: High-temperature rolling: The workpiece is rolled after being taken out of the furnace in step S5. When rolling begins, the temperature of the workpiece is 1000-1100°C; S6.2: Low temperature rolling. The workpiece is rolled again after the above high temperature rolling. When the rolling begins, the temperature of the workpiece is 900~950℃.

[0011] In the above technical solution, the rolling step is divided into two stages. Partial rolling is first performed in the high-temperature rolling stage (which is a relatively easy-to-process stage) to reduce the difficulty of subsequent processing. Then, further rolling is performed in the low-temperature processing stage. The austenite grains in the workpiece are refined within the temperature range of the low-temperature processing stage. That is, this solution performs partial rolling operations in the initial stage of the rolling step to reduce the difficulty of subsequent processing, and then controls the final stage of the rolling step within a suitable temperature range to provide an environment for austenite grain refinement, so that the austenite grains are well refined and mixed crystal defects are eliminated, thereby obtaining a bearing ring product with simultaneously improved strength, toughness, and corrosion resistance, thereby further extending the service life.

[0012] Furthermore, in the technical solution of the present invention, there are at least the following three mechanisms for further refining austenite grains: ① Dynamic recrystallization of austenite is the phenomenon that during the high-temperature plastic deformation of metal materials, austenite grains form new grains through nucleation and growth; ②Austenite metadynamic recrystallization is a special recrystallization behavior that occurs in metal materials during hot working. It specifically refers to the process in which the formed dynamic recrystallization nuclei or ungrown recrystallized grains grow under high temperature holding conditions after the hot deformation stops. ③ Static recrystallization of austenite refers to the process in which, after the thermal deformation stops, austenite forms new non-distorted equiaxed grains through nucleation and growth during the high-temperature holding process, driven by the deformation storage energy; The present invention fully utilizes the above three austenite refinement mechanisms through the coordinated control of low temperature and deformation amount, thereby achieving significant improvement in austenite grain refinement and mixed crystal.

[0013] In the initial stage of rolling, the workpiece is difficult to roll, which is mainly manifested in the thickening of the workpiece. Therefore, in this stage, the workpiece is partially rolled at a higher temperature to form a specification shape that is easier to withstand stress and can be further rolled. Therefore, in a further embodiment, in S6.1, the deformation of the workpiece is 20~50%.

[0014] In a further embodiment, in S6.2, the deformation of the workpiece is 50-70%, subject to the final requirement of meeting the product specifications.

[0015] The final rolling temperature has a great influence on the grain growth during the cooling process of the product. If the final rolling temperature is too high, the austenite grains will grow further and form coarse grains. Therefore, in a further embodiment, in S6.2, at the end of rolling, the temperature of the workpiece is 820~880℃ to prevent further grain growth after the end of rolling.

[0016] In some embodiments, after step S6.1 is completed, the workpiece is cooled naturally to 900-950° C. before step S6.2 is started.

[0017] In some embodiments, after step S6.1 is completed, the time for the workpiece to naturally cool down is 85 to 105 seconds.

[0018] The bearing ring is prepared by the preparation process described in any of the above technical solutions.

[0019] In some embodiments, the bearing ring is made of high-carbon chromium-molybdenum bearing steel.

[0020] Increasing the deformation of the workpiece is beneficial to the refinement of austenite grains. This is because plastic deformation increases the dislocation density within the austenite, forming deformation bands and slip lines. The stored distortion can become the driving force for recrystallization. The greater the deformation, the higher the dislocation density, the more significantly the recrystallization nucleation rate increases, and the more obvious the refinement effect. In some fields, such as the wind power generation field, as wind turbines become larger, the size of bearings gradually increases, resulting in a decrease in the total deformation of the corresponding bearing rings during thermal deformation (relative to small-sized bearing rings), which is not conducive to the refinement of the bearing ring structure; therefore, in a preferred embodiment, the outer diameter of the bearing ring is greater than 6m and the inner diameter is greater than 5.2m.

[0021] The rotating component uses the bearing ring described in any of the above technical solutions.

[0022] In some embodiments, the rotating component is a generator; In some embodiments, the rotating component is a generator used in a wind power generation device.

[0023] In summary, the technical solution of the present invention has the following main beneficial effects: Compared with the existing technology, the technical solution of the present invention achieves a significant improvement in austenite grain refinement and mixed crystals through the coordinated control of low temperature and deformation amount, thereby improving the mechanical properties and service life of the bearing ring products.

[0024] Furthermore, in the initial stage of rolling, the workpiece is partially rolled at a higher temperature to form a part that is easier to process, and then further rolled after the temperature is lowered to meet the final product specifications.

[0025] Furthermore, by optimizing the final rolling temperature, further grain growth after the rolling is completed can be prevented.

[0026] Further or more detailed beneficial effects will be described in conjunction with specific examples in the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a state diagram of the workpiece in different steps in a specific implementation method.

[0028] In the figure: (a) is the state diagram of the workpiece in the upsetting step, (b) is the state diagram of the workpiece in the punching step, (c) is the state diagram of the workpiece in the pre-rolling step, (d) is the state diagram of the workpiece in the high-temperature rolling step, and (e) is the state diagram of the workpiece in the low-temperature rolling step. DETAILED DESCRIPTION

[0029] The present invention will be further explained with reference to the following embodiments: The core technical problem faced by the technical solution of the embodiment of the present application comes from the inventor's accurate understanding of the existing technology. Therefore, how to improve the service life of the bearing ring is a technical problem that the inventor urgently needs to solve.

[0030] It should be noted that the embodiments do not constitute a limitation on the scope of protection of the claims of the present invention. Based on the technical concepts provided / proven by the embodiments, all technical solutions that can be reasonably anticipated by technical personnel in the relevant technical field should be included in the scope of protection of the claims of the present invention.

[0031] The embodiments are described in detail as follows: Example 1:

[0032] Please refer to the attached for the status of the thermal processing process. Figure 1 A preparation process for a bearing ring is disclosed. The bearing ring uses 100CrMo7-3 bearing steel and is used for manufacturing wind power gearbox bearings. Based on basic theoretical reasoning, it can be seen that the process of this embodiment is also applicable to bearing rings of other brands.

[0033] The composition of 100CrMo7-3 bearing steel is Fe-0.94C-0.24Si-0.69Mn-1.68Cr-0.21Mo-0.17Ni-0.0004O (mass percentage). The billet is a spheroidized annealed bar with a diameter of 250 mm and a length of 580 mm.

[0034] First, the billet is heated to 1150°C in a heating furnace, kept at this temperature for 1.5-4 hours, and then taken out of the furnace and axially upset to 180 mm. Then, a punch with a diameter of 140 mm was used for punching; After punching, the blank is flattened to 180 mm; Then it is pre-rolled on a rolling mill to a thickness of 100 mm; Return to the original heating furnace and keep the temperature for 1 hour before preparing for fine rolling; After being taken out of the furnace, the rolling is carried out in two stages. In the first stage, the temperature of the billet when it starts to be rolled is 1100℃, the height of the workpiece gradually decreases from 180 mm to 170 mm, and the thickness gradually decreases from 100 mm to 75 mm. The thickness reduction is 25%, and the total compression ratio is 1.41.

[0035] After 94 s of holding temperature, the temperature of the billet dropped to 950°C and the second stage of rolling was carried out. The thickness gradually decreased from 75 mm to 50 mm, while the height remained unchanged. The total compression ratio was 1.5 and the final rolling temperature was 850°C.

[0036] The austenite grain size of the rolled workpiece was tested to be 62.4 μm, the grain size was relatively uniform, and there was no mixed crystal phenomenon.

[0037] Comparative Example 1: The raw materials and basic process were the same as in Example 1, with the only difference being that the rolling process after remelting was conventional, completing the deformation in one step. The final rolling temperature was 931°C. Observation of the microstructure after rolling revealed an average austenite grain size of 92.5 μm, with significant mixed grains.

[0038] Comparative Example 2: The raw materials and basic process were the same as in Example 1. After returning to the furnace, the rolling process was carried out in two stages. The difference was that the interval between the two stages was 54 seconds, resulting in a final rolling temperature of 901°C. Due to the insufficient interval and the high final rolling temperature, the austenite grain size was slightly finer than that in Comparative Example 1, reaching 75.4 μm. However, there was a significant mixed crystal phenomenon.

[0039] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0040] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A process for preparing a bearing ring, comprising a thermal deformation process, wherein the thermal deformation process comprises the following steps: S1: upsetting, S2: punching, S3: leveling, S4: pre-rolling, S5: reheating, S6: rolling; Its characteristics are: The above step S6 includes the following steps: S6.1: High-temperature rolling: The workpiece is rolled after being taken out of the furnace in step S5. When rolling begins, the temperature of the workpiece is 1000-1100°C; S6.2: Low temperature rolling. The workpiece is rolled again after the above high temperature rolling. When the rolling begins, the temperature of the workpiece is 900~950℃.

2. The preparation process according to claim 1, wherein: In S6.1, the deformation of the workpiece is 20~50%.

3. The preparation process according to claim 1 or 2, characterized in that: In S6.2, the deformation of the workpiece is 50~70%.

4. The preparation process according to claim 3, characterized in that: In S6.2, at the end of rolling, the temperature of the workpiece is 820~880℃.

5. The preparation process according to claim 1, wherein: After step S6.1 is completed, the workpiece is cooled naturally to 900-950°C and then S6.2 is started.

6. The preparation process according to claim 5, characterized in that: After step S6.1 is completed, the time for the workpiece to cool down naturally is 85~105s.

7. Bearing ring, characterized in that: Prepared by the preparation process according to any one of claims 1 to 6.

8. The bearing ring according to claim 7, characterized in that: Made of high carbon chromium-molybdenum bearing steel.

9. The bearing ring according to claim 7 or 8, characterized in that: The outer diameter of the bearing ring is greater than 6m, and the inner diameter is greater than 5.2m.

10. Rotating component, characterized in that: The bearing ring according to any one of claims 7 to 9 is used.

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