Method for improving wear resistance of bearing

Abstract

The invention relates to the technical field of bearing surface treatment, in particular to a method for improving the wear resistance of a bearing, which comprises the following steps: S1, pretreating the working surface of the bearing, and fixing the bearing on a lathe for turning treatment after pretreatment; s2, after turning treatment, carrying out electric pulse treatment on the working surface of the bearing; and S3, after the electric pulse treatment, carrying out ultrasonic rolling treatment on the working surface of the bearing. Electric pulse treatment is carried out before ultrasonic rolling treatment is carried out on the working surface of the bearing, the pulse current and the ultrasonic rolling technology are combined, the plastic flow of the surface layer of the workpiece is increased through the electric pulse current, and micro cracks are accelerated to heal under the ultrasonic rolling effect; the method can effectively solve the problem that the thickness of a strengthened layer is small due to ultrasonic rolling strengthening, micro cracks on the surface of a sample can be avoided, comprehensive strengthening treatment on the surface of a bearing steel material is achieved, the material surface strengthening effect is enhanced, and the service performance of a structural part is improved.

Description

Technical Field

[0001] The invention relates to the technical field of bearing surface treatment, and in particular to a method for improving the wear resistance of a bearing. Background Art

[0002] Bearings are key basic components of mechanical transmission systems and are widely used in major technical equipment such as aerospace, high-speed rail units, and large shield machines. They often serve under harsh working conditions such as variable loads, variable speeds, high DN values, intermittent service, and oil outages.

[0003] When the bearing is working, the rolling element will have a small relative movement near the contact area of ​​the raceway, which makes it impossible for the lubricating oil to be redistributed on the contact surface and causes the metal surfaces to contact directly, causing wear of the metal on the contact surface. This phenomenon is called fretting wear of the bearing. Fretting wear can cause scratches and pits on the bearing surface. In severe cases, it can cause the initiation and expansion of fretting cracks on the bearing surface, and even fracture failure. Since most of the wear starts from the surface of the parts, an effective surface modification method is sought to improve the wear resistance of the bearing.

[0004] At present, the main method of surface processing of bearing rings is grinding after heat treatment. As a relatively new surface strengthening technology, surface ultrasonic rolling combines traditional rolling technology and ultrasonic processing technology. It uses ultrasonic high-frequency vibration to impact the pressure head with a certain static pressure on the surface of the workpiece at high frequency, so that the metal material produces a large elastic-plastic deformation, thereby achieving the effect of processing strengthening on the surface of the workpiece. As an emerging surface strengthening technology, ultrasonic rolling technology has the advantages of significantly improving surface quality, simple process, energy saving and environmental protection, and high efficiency. It has been widely used in the automotive industry, gear manufacturing industry, aerospace and other fields. Compared with laser polishing and laser shot peening technology, the processing cost of ultrasonic rolling technology is lower, the equipment maintenance is very convenient, and the precision control during the processing process is also easier. Therefore, the use of ultrasonic rolling surface strengthening technology to strengthen the wear resistance of bearings has good application prospects. However, the disadvantage is that the significant hardening of the surface strengthening layer caused by severe plastic deformation greatly hinders the further plastic deformation and strengthening of the metal inside, which leads to a small thickness of the surface hardened layer of the sample after ultrasonic rolling technology treatment. Patent CN 114438307 A combines laser impact and ultrasonic rolling to obtain residual compressive stress with larger amplitude and deeper affected layer. However, this technology requires the sample to be processed twice, the process steps are relatively complicated, and it takes a long time.

[0005] As an advanced field treatment technology for metal materials, electric pulses can affect the plasticity, recrystallization, phase transformation, microstructure evolution, as-cast microstructure and fatigue life of metal materials. When pulse current passes through metal materials, a large number of free electrons with directional drift are generated. The drifting electron group frequently and directionally hits the dislocations, which will produce an electron wind force similar to the external stress on the dislocation segment, promoting the movement of the dislocation on its slip plane. When electric pulses are applied to the plastic processing of metal materials, the electric pulses accelerate phase transformation, dislocation mobility and atomic diffusion, significantly reducing the work hardening of the material and the number of defects, thereby reducing the deformation resistance and significantly improving the surface quality of the parts.

[0006] There is no related report on the composite strengthening of bearings using pulse current-ultrasonic rolling in the prior art. Summary of the invention

[0007] In view of the technical problem of wear on the working surface of a bearing, the present invention aims to provide a method for improving the wear resistance of a bearing, thereby improving the hardness and wear resistance of the working surface of the bearing.

[0008] The present invention provides a method for improving the anti-wear performance of a bearing, comprising the following steps: S1. Pre-treat the working surface of the bearing. After pre-treatment, fix the bearing on a lathe for turning. S2. After turning, the working surface of the bearing is subjected to electric pulse treatment; S3. After the electric pulse treatment, the working surface of the bearing is subjected to ultrasonic rolling treatment.

[0009] Furthermore, in step S1, the method for pre-treating the working surface of the bearing includes sequentially grinding, polishing, and ultrasonic cleaning the working surface of the bearing.

[0010] Furthermore, in step S1, the turning process conditions include a turning speed of 25-30 m / min and a feed speed of 0.05-0.1 mm / rev.

[0011] Furthermore, in step S2, the electric pulse treatment includes applying a pulse current treatment to the working surface of the bearing using a pulse power supply.

[0012] Furthermore, the process parameters of the electric pulse treatment include pulse voltage of 6~8kV, pulse width of 55~65μs, pulse frequency of 580~620Hz, and root mean square current density of 0.60~1.40A / mm 2 , peak current density is 4.70~9.70A / mm 2 .

[0013] Furthermore, in step S3, the ultrasonic rolling treatment includes using an ultrasonic rolling head perpendicular to the tangent line of the bearing working surface to perform ultrasonic rolling treatment on the bearing working surface.

[0014] Furthermore, the ultrasonic rolling head is a hard alloy ball.

[0015] Furthermore, the ultrasonic rolling treatment process parameters include an ultrasonic rolling amplitude of 6 to 10 μm, an ultrasonic rolling frequency of 25 to 30 kHz, an ultrasonic rolling static pressure of 500 to 1100 N, and an ultrasonic rolling number of 5 to 15 times.

[0016] Furthermore, the bearing is made of GCr15 steel.

[0017] The principle of the present invention is: the present invention performs electric pulse treatment on the working surface of the bearing before ultrasonic rolling treatment, combines pulse current with ultrasonic rolling technology, and uses electric pulse current to increase the plastic flow of the surface of the workpiece, so that microcracks are accelerated to heal under the action of ultrasonic rolling. It can effectively solve the problem of small thickness of the strengthening layer caused by ultrasonic rolling strengthening, and can avoid the appearance of microcracks on the surface of the sample, realize comprehensive strengthening treatment of the surface of the bearing steel material, enhance the surface strengthening effect of the material, and improve the service performance of the structural parts.

[0018] The beneficial effects of the present invention are: (1) Compared with the existing complex methods such as improving the production process and optimizing the components to improve the wear resistance of the bearing working surface, the treatment method of the present invention is simple in process and low in cost.

[0019] (2) The present invention utilizes a combination of pulse current and ultrasonic rolling technology to significantly improve the working surface quality of the bearing. It does not require subsequent fine grinding, polishing, grinding and other complicated processes, and can directly meet the processing requirements, thereby reducing the complexity of multiple processes, reducing costs and improving processing efficiency.

[0020] (3) The present invention can refine the grains of the surface layer of the bearing metal material and generate a large number of microstructures such as dislocations and twins, thereby effectively improving the fatigue strength and wear resistance of the bearing. The hardness of the bearing working surface after treatment is 840~850HV 0.2 Compared with untreated bearings, the hardness is increased by 20%~30%, the micro-friction coefficient is reduced by 20%, the wear is reduced, the fatigue strength and service life are improved. At the same time, compared with bearings treated only with ultrasonic rolling, the thickness of the hardened layer is increased by more than 1 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a curve chart of the microhardness variation trend of bearings in Examples 1 and 2 and Comparative Examples 1 and 2 according to the specific implementation manner of the present invention.

[0023] Figure 2 It is a curve chart showing the variation trend of the bearing friction coefficient of Examples 1 and 2 and Comparative Examples 1 and 2 according to the specific implementation manner of the present invention.

[0024] Figure 3 EBSD images of the surface grains of the bearings of Example 2 and Comparative Example 2 according to the specific implementation manner of the present invention; Figure 3 Figure A is the EBSD image of the surface grains of the bearing of comparative example 2, and Figure B is the EBSD image of the surface grains of the bearing of embodiment 2. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] Example 1 A method for improving the wear resistance of a bearing comprises the following steps: (1) The working surface of the GCr15 steel bearing was ground and polished with 2000# sandpaper to make the surface smooth, and then the surface was cleaned by ultrasonic cleaning in anhydrous ethanol for 5 minutes and dried with a hair dryer for later use to complete the pretreatment.

[0027] (2) The bearing after the work surface pretreatment in step (1) is fixed on the machine tool for turning, with a turning speed of 25 m / min and a feed speed of 0.05 mm / rev.

[0028] (3) The working surface of the bearing treated in step (2) is subjected to electric pulse treatment. The electric pulse uses a pulse power supply to apply a pulse current. The pulse current is a positive sharp wave high-energy narrow pulse width current: the pulse voltage is 6 kV, the pulse width is 55 μs, the pulse frequency is 580 Hz, and the root mean square current density is 0.60 A / mm 2 , the peak current density is 4.70A / mm 2 .

[0029] (4) Ultrasonic rolling treatment of the working surface of the bearing treated in step (3): The ultrasonic rolling head is always perpendicular to the tangent of the working surface of the bearing, and the working surface of the bearing is subjected to ultrasonic rolling treatment. The ultrasonic rolling head is a carbide ball, and the process parameters of the ultrasonic rolling treatment are set as follows: amplitude of 8 μm, frequency of 27 kHz, static pressure of 500 N, and rolling times of 10 times.

[0030] Example 2 A method for improving the wear resistance of a bearing comprises the following steps: (1) The working surface of the GCr15 steel bearing was ground and polished with 2000# sandpaper to make the surface smooth, and then the surface was cleaned by ultrasonic cleaning in anhydrous ethanol for 5 minutes and dried with a hair dryer for later use to complete the pretreatment.

[0031] (2) The bearing after the working surface pretreatment in step (1) is fixed on the machine tool for turning, with a turning speed of 25 m / min and a feed speed of 0.05 mm / rev.

[0032] (3) The working surface of the bearing treated in step (2) is subjected to electric pulse treatment. The electric pulse uses a pulse power supply to apply a pulse current. The pulse current is a positive sharp wave high-energy narrow pulse width current: the pulse voltage is 7 kV, the pulse width is 60 μs, the pulse frequency is 590 Hz, and the root mean square current density is 0.90 A / mm 2 , the peak current density is 6.40A / mm 2 .

[0033] (4) Ultrasonic rolling treatment of the bearing working surface treated in step (3): The ultrasonic rolling head is always perpendicular to the tangent of the bearing working surface, and the bearing working surface is subjected to ultrasonic rolling treatment. The ultrasonic rolling head is a carbide ball, and the ultrasonic rolling treatment process parameters are set as follows: amplitude of 10 μm, frequency of 30 kHz, static pressure of 800 N, and rolling times of 12 times.

[0034] Example 3 A method for improving the wear resistance of a bearing comprises the following steps: (1) The working surface of the GCr15 steel bearing was ground and polished with 2000# sandpaper to make the surface smooth, and then the surface was cleaned by ultrasonic cleaning in anhydrous ethanol for 5 minutes and dried with a hair dryer for later use to complete the pretreatment.

[0035] (2) The bearing after the working surface pretreatment in step (1) is fixed on the machine tool for turning, with a turning speed of 30 m / min and a feed speed of 0.10 mm / rev.

[0036] (3) The working surface of the bearing treated in step (2) is subjected to electric pulse treatment. The electric pulse uses a pulse power supply to apply a pulse current. The pulse current is a positive sharp wave high-energy narrow pulse width current: the pulse voltage is 8 kV, the pulse width is 65 μs, the pulse frequency is 620 Hz, and the root mean square current density is 1.40 A / mm 2 , the peak current density is 9.70A / mm 2 .

[0037] (4) Ultrasonic rolling treatment of the working surface of the bearing treated in step (3): The ultrasonic rolling head is always perpendicular to the tangent of the working surface of the bearing, and the working surface of the bearing is subjected to ultrasonic rolling treatment. The ultrasonic rolling head is a carbide ball, and the process parameters of the ultrasonic rolling treatment are set as follows: amplitude of 6 μm, frequency of 25 kHz, static pressure of 1100 N, and rolling times of 5 times.

[0038] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not contain step (3).

[0039] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the GCr15 steel bearing in Comparative Example 2 is not treated.

[0040] Test Case The bearings obtained in the embodiments and comparative examples were tested as follows: (1) Microhardness Figure 1 The microhardness variation trend curves of the bearings in Examples 1 and 2 and Comparative Examples 1 and 2 are shown. Figure 1 It can be seen that the microhardness of the surface layer of the GCr15 bearing in Comparative Example 2 that has not been treated by the present invention is about 675 HV 0.2 The surface microhardness of the comparative example 1 which was subjected to ultrasonic rolling treatment only was about 820 HV. 0.2 , the hardened layer is about 100μm. The surface microhardness of Examples 1 and 2 of the present invention can reach 840~850HV 0.2 , which is 20% to 30% higher than that of comparative example 2, and the thickness of the hardened layer is increased to 200μm. At the same time, it can be seen that compared with ordinary bearings that are only subjected to ultrasonic rolling treatment, the microhardness of the surface layer and the thickness of the hardened layer of the bearings treated by the method of the present invention are significantly improved, and the thickness of the hardened layer is increased by 1 times.

[0041] (2) Fretting friction coefficient Figure 2 The variation trend curves of the bearing friction coefficients of Examples 1 and 2 and Comparative Examples 1 and 2 are shown. Figure 2It can be seen that all bearing parts experience a running-in period with a rapid increase in friction coefficient, and finally enter a stable running-in period with a stable friction coefficient. Compared with the untreated comparative example 2, the micro-friction coefficients of the bearing samples of Examples 1 and 2 treated by the present invention are reduced. The micro-friction coefficient of the bearing of Comparative Example 2 that has not been treated by the present invention is about 0.45, and the micro-friction coefficient of the samples of Examples 1 and 2 treated by the method of the present invention is about 0.36, and the micro-friction coefficient of the present invention is reduced by about 20%.

[0042] (3) Microstructure Figure 3 The EBSD images of the surface grains of the bearings of Example 2 and Comparative Example 2 are shown. Figure 3 A is the EBSD image of the surface grains of the bearing in comparative example 2, and B is the EBSD image of the surface grains of the bearing in embodiment 2. It can be seen that the surface grain size of the bearing obtained in embodiment 2 of the present invention is significantly reduced, resulting in grain refinement, indicating that the processing method of the present invention can significantly refine the surface microstructure of the material and produce a fine grain strengthening effect.

[0043] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person skilled in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and they shall be within the scope of protection of the present invention.

Claims

1. A method for improving the wear resistance of a bearing, characterized in that: The steps include: S1. Pre-treat the working surface of the bearing. After pre-treatment, fix the bearing on a lathe for turning. S2. After turning, the working surface of the bearing is subjected to electric pulse treatment; S3. After the electric pulse treatment, the working surface of the bearing is subjected to ultrasonic rolling treatment.

2. The method for improving the anti-wear performance of a bearing according to claim 1, characterized in that: In step S1, the method for pre-treating the working surface of the bearing includes sequentially grinding, polishing, and ultrasonic cleaning the working surface of the bearing.

3. The method for improving the anti-wear performance of a bearing according to claim 1, characterized in that: In step S1, the turning process conditions include a turning speed of 25-30 m / min and a feed speed of 0.05-0.1 mm / rev.

4. The method for improving the anti-wear performance of a bearing according to claim 1, characterized in that: In step S2, the electric pulse treatment includes applying a pulse current treatment to the working surface of the bearing using a pulse power supply.

5. The method for improving the anti-wear performance of a bearing according to claim 4, characterized in that: The process parameters of the electric pulse treatment include pulse voltage of 6~8kV, pulse width of 55~65μs, pulse frequency of 580~620Hz, and root mean square current density of 0.60~1.40A / mm 2 , peak current density is 4.70~9.70A / mm 2 .

6. The method for improving the anti-wear performance of a bearing according to claim 1, characterized in that: In step S3, the ultrasonic rolling treatment includes using an ultrasonic rolling head perpendicular to the tangent line of the bearing working surface to perform ultrasonic rolling treatment on the bearing working surface.

7. The method for improving the anti-wear performance of a bearing according to claim 6, characterized in that: The ultrasonic rolling head is a carbide ball.

8. The method for improving the anti-wear performance of a bearing according to claim 6, characterized in that: The ultrasonic rolling treatment process parameters include ultrasonic rolling amplitude of 6~10μm, ultrasonic rolling frequency of 25~30kHz, ultrasonic rolling static pressure of 500~1100N, and ultrasonic rolling times of 5~15 times.

9. The method for improving the anti-wear performance of a bearing according to any one of claims 1 to 8, characterized in that: The bearing material is GCr15 steel.

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