Efficient preparation method of bearing steel spheroidizing annealing structure sample

Abstract

The invention relates to an efficient preparation method of a bearing steel spheroidizing annealing structure sample, and belongs to the technical field of metallographic test piece preparation. In order to solve the problem that an existing bearing steel spheroidizing annealing structure sample is low in preparation efficiency, the invention provides an efficient preparation method of a bearing steel spheroidizing annealing structure sample, and the efficient preparation method comprises the steps of improving a sample grinding procedure, optimizing a manual polishing method and finely controlling the grinding speed. One-step polishing is reduced by adjusting the size of grinding particles, meanwhile, a sample is controlled to move on a grinding disc according to a circular rotating track during manual polishing, vectors of the sample in all directions are evenly distributed, it is guaranteed that granular pearlite in a spheroidizing annealing structure of the bearing steel is complete and clear, and the conditions of illusion and deformation structures are avoided; the temperature, time and the like of the bearing steel spheroidizing annealing process can be evaluated more comprehensively, and the problems that the bearing steel spheroidizing annealing structure sample preparation time is long, and the first-pass yield of sample preparation is low are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallographic specimen preparation, and in particular relates to a high-efficiency preparation method for a bearing steel spheroidizing annealing structure specimen. Background Art

[0002] The inspection of the spheroidized annealed microstructure of bearing steel mainly evaluates the size, shape and quantity of spheroidal pearlite and point-like carbides in the sample. Therefore, whether the microstructure can be accurately and quickly displayed in the sample preparation process is the basis of this project inspection. Since the shape of lamellar pearlite changes from lamellar to granular after spheroidizing annealing, it is difficult to prepare artificial samples. The granular pearlite in the microstructure caused by sample preparation is often irregular, directional and unclear.

[0003] The preparation of the existing bearing steel spheroidizing annealing microstructure metallographic sample gradually reduces the scratch depth and improves the surface finish through rough grinding, fine grinding, rough polishing, fine polishing and fine polishing, so as to provide a high-quality sample surface for subsequent microscopic observation and analysis. The main purpose of rough polishing is to remove the deep scratches and unevenness left on the sample surface by fine grinding, so as to make the sample surface smoother; the main purpose of fine polishing is to further smooth the sample surface and eliminate the fine scratches and defects left by rough polishing; and the process of fine polishing is to completely eliminate all scratches and defects on the sample surface so that the surface achieves a mirror effect. The three steps of rough polishing, fine polishing and fine polishing each undertake important tasks in the grinding process of the spheroidizing annealing microstructure sample. If the rough polishing is omitted, the fine polishing process will take longer time and more workload to eliminate the deep scratches left by fine grinding, and may not even achieve the ideal polishing effect; if the fine polishing is omitted, the fine polishing process will be affected by the residual scratches and defects on the sample surface, resulting in an unsatisfactory final polishing effect; and omitting fine polishing will cause the scratches and defects on the sample surface to seriously affect the results of microscopic observation, and may even lead to wrong conclusions.

[0004] How to further improve the efficiency of sample preparation for spheroidizing annealing microstructure of bearing steel on the basis of ensuring accurate sample preparation is an urgent problem to be solved in this field. Summary of the invention

[0005] In order to solve the problem of low efficiency in the preparation of existing bearing steel spheroidizing annealing structure samples, the present invention provides a high-efficiency preparation method for bearing steel spheroidizing annealing structure samples.

[0006] The technical solution of the present invention:

[0007] An efficient preparation method for a bearing steel spheroidized annealing microstructure sample comprises improving the sample grinding process, optimizing the manual polishing technique and finely controlling the grinding speed; the grinding process comprises coarse grinding, fine grinding, coarse polishing and fine polishing; the manual polishing technique is fine polishing using a circular polishing trajectory for polishing three times; the finely controlling the grinding speed is to set the grinding disc rotation speed to 100-200 rpm.

[0008] Furthermore, the grinding particle size of the coarse grinding is 42#, the grinding particle size of the fine grinding is 320#, the grinding particle size of the rough polishing is 800#, and the grinding particle size of the fine polishing is W5.

[0009] Furthermore, during the rough polishing and fine polishing, the grinding disc rotates in a clockwise direction.

[0010] Furthermore, during the first and second fine polishing, the sample is held in a hand and moves in a circular motion on the grinding disc along a circular polishing trajectory. During the motion, the sample is tilted appropriately so that the surface of the sample partially and briefly contacts the grinding disc, and the sample rotates in a clockwise direction while in contact.

[0011] Furthermore, during the first polishing of the fine polishing, the upper part of the sample surface is partially and briefly in contact with the grinding disc, and the angle of the sample rotation in the clockwise direction is 60 to 90 degrees.

[0012] Furthermore, during the second polishing of the fine polishing manual polishing, the lower half of the sample surface partially and briefly contacts the grinding disc, and the angle of the sample rotation in the clockwise direction is 60 to 90 degrees.

[0013] Furthermore, during the third polishing of fine polishing, the sample is held and moved in a circular motion on the grinding disc along a circular polishing track so that the entire surface of the sample contacts the grinding disc, and the sample does not rotate during the contact process.

[0014] Furthermore, the grinding disc rotation speed is set to 150 rpm.

[0015] Furthermore, the time for the rough grinding is 10 to 20 seconds, the time for the fine grinding is 10 to 20 seconds, the time for the rough polishing is 30 to 60 seconds, the time for the first polishing is 10 to 20 seconds, the time for the second polishing is 10 to 20 seconds, and the time for the third polishing is 10 to 20 seconds.

[0016] Beneficial effects of the present invention:

[0017] The present invention provides an efficient preparation method for a bearing steel spheroidizing annealing structure sample, which mainly optimizes the grinding and polishing process, including adjusting the size of the grinding particles to reduce one step of polishing, and at the same time combining the optimization of the manual polishing technique to improve the sample preparation efficiency and sample preparation quality. During manual polishing, the present invention controls the sample to move on a circular rotating trajectory on the grinding disc, so that the vectors of the sample in all directions are evenly distributed, and the roundness, size, and stacking of the granular pearlite structure can be fully displayed, ensuring that the granular pearlite in the spheroidizing annealing structure of the bearing steel is complete and clear, without false images and deformed structure conditions, and can more comprehensively evaluate the temperature, time, etc. of the spheroidizing annealing process of the bearing steel, solving the problem of a long preparation time for the spheroidizing annealing structure sample of the bearing steel and a low one-time qualified rate of the sample preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 and Figure 2 The metallographic micrograph of the spheroidizing annealing sample of the bearing steel prepared in Example 1;

[0019] Figure 3 and Figure 4 This is a microscopic photo of the metallographic structure of the spheroidizing annealing structure sample of the bearing steel prepared in Comparative Example 1;

[0020] Figure 5 This is a schematic diagram of the circular polishing trajectory of the first polishing of the fine polishing of the present invention;

[0021] Figure 6 This is a schematic diagram of the circular polishing trajectory of the second polishing of the fine polishing of the present invention;

[0022] Figure 7 This is a schematic diagram of the circular polishing trajectory of the third polishing of the fine polishing of the present invention;

[0023] Figure 8 It is a schematic diagram of the relationship between the grinding relative speed and the grinding disc rotation speed;

[0024] Fig. 9 Schematic diagram of the distribution of velocity vectors at different grinding disc speeds;

[0025] Fig.10 Schematic diagram of the conventional arc-shaped long-tail polishing trajectory in Comparative Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0027] Example 1

[0028] This embodiment provides an efficient preparation method for a spheroidized annealed microstructure sample of a bearing steel, including improving the sample grinding process, optimizing the manual polishing technique, and finely controlling the grinding speed.

[0029] In this embodiment, the grinding process includes coarse grinding, fine grinding, coarse polishing and fine polishing. The grinding particle size of coarse grinding is 42#, the grinding particle size of fine grinding is 320#, the grinding particle size of coarse polishing is 800#, and the grinding particle size of fine polishing is W5.

[0030] In this embodiment, the time for rough grinding is 10 seconds, the time for fine grinding is 10 seconds, and the time for rough polishing is 30 seconds.

[0031] During the rough polishing and fine polishing in this embodiment, the rotation direction of the grinding disc is clockwise, and the rotation speed of the grinding disc is 150 rpm.

[0032] In this embodiment, the fine polishing adopts a circular polishing track and polishes three times.

[0033] Fine polishing manual polishing During the first polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the upper part of the sample surface briefly contacts the grinding disc. Figure 5 As shown, the sample rotates clockwise at an angle of 45°; the first polishing time is 10S;

[0034] Fine polishing manual polishing During the second polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the lower half of the sample surface briefly contacts the grinding disc. Figure 6 As shown, the sample rotates clockwise at an angle of 45°; the second polishing time is 10S;

[0035] Fine polishing manual polishing During the third polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track, such as Figure 7 As shown, the entire surface of the sample is in contact with the grinding disc, and the sample does not rotate during the contact process; the third polishing time is 10S.

[0036] like Figure 8 , Fig. 9 As shown, the present invention analyzes and optimizes the grinding speed of the polishing process through the relationship between the grinding relative speed and the grinding wheel rotation speed and the distribution of the speed vectors of the grinding wheel at different rotation speeds during the grinding process. Through experiments and analysis, the grinding wheel rotation speed is set to 150 rpm as the optimal rotation speed, which can achieve a fast and high-quality polishing effect.

[0037] Example 2

[0038] This embodiment provides an efficient preparation method for a spheroidized annealed microstructure sample of a bearing steel, including improving the sample grinding process, optimizing the manual polishing technique, and finely controlling the grinding speed.

[0039] In this embodiment, the grinding process includes coarse grinding, fine grinding, coarse polishing and fine polishing. The grinding particle size of coarse grinding is 42#, the grinding particle size of fine grinding is 320#, the grinding particle size of coarse polishing is 800#, and the grinding particle size of fine polishing is W5.

[0040] In this embodiment, the time for coarse grinding is 15 seconds, the time for fine grinding is 15 seconds, and the time for rough polishing is 45 seconds.

[0041] During the rough polishing and fine polishing in this embodiment, the rotation direction of the grinding disc is clockwise, and the rotation speed of the grinding disc is 150 rpm.

[0042] In this embodiment, the fine polishing adopts a circular polishing track and polishes three times.

[0043] Fine polishing manual polishing During the first polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the upper part of the sample surface temporarily contacts the grinding disc. The sample rotates clockwise at a rotation angle of 60°. The first polishing time is 15S.

[0044] Fine polishing manual polishing During the second polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the lower half of the sample surface is partially in contact with the grinding disc for a short time. The sample rotates clockwise at a rotation angle of 60°. The second polishing time is 15S.

[0045] During the third polishing of fine polishing, hold the sample and make circular motion on the grinding disc along the circular polishing trajectory so that the entire surface of the sample contacts the grinding disc. The sample does not rotate during the contact process; the time for the third polishing is 15S.

[0046] Example 3

[0047] This embodiment provides an efficient preparation method for a spheroidized annealed microstructure sample of a bearing steel, including improving the sample grinding process, optimizing the manual polishing technique, and finely controlling the grinding speed.

[0048] In this embodiment, the grinding process includes coarse grinding, fine grinding, coarse polishing and fine polishing. The grinding particle size of coarse grinding is 42#, the grinding particle size of fine grinding is 320#, the grinding particle size of coarse polishing is 800#, and the grinding particle size of fine polishing is W5.

[0049] In this embodiment, the time for rough grinding is 20 seconds, the time for fine grinding is 20 seconds, and the time for rough polishing is 60 seconds.

[0050] During the rough polishing and fine polishing in this embodiment, the rotation direction of the grinding disc is clockwise, and the rotation speed of the grinding disc is 150 rpm.

[0051] In this embodiment, the fine polishing adopts a circular polishing track and polishes three times.

[0052] Fine polishing manual polishing During the first polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the upper part of the sample surface temporarily contacts the grinding disc. The sample rotates clockwise at a rotation angle of 90°. The first polishing time is 20 seconds.

[0053] Fine polishing manual polishing During the second polishing, hold the sample and make circular motion on the grinding disc along the circular polishing track. During the motion, tilt the sample appropriately so that the lower half of the sample surface temporarily contacts the grinding disc. The sample rotates clockwise at an angle of 90°. The second polishing time is 20 seconds.

[0054] During the third polishing of fine polishing, hold the sample and make circular motion on the grinding disc along the circular polishing trajectory so that the entire surface of the sample contacts the grinding disc. The sample does not rotate during the contact process; the time for the third polishing is 20S.

[0055] Comparative Example 1

[0056] This comparative example adopts a preparation method for a conventional bearing steel spheroidizing annealing tissue sample, and the grinding process includes coarse grinding, fine grinding, coarse polishing, fine polishing and fine polishing. The grinding particle size of coarse grinding is 42#, the grinding particle size of fine grinding is 280#, the grinding particle size of coarse polishing is 600#, the grinding particle size of fine polishing is W7, and the grinding particle size of fine polishing is W2.5; wherein the time for coarse grinding is 20S, the time for fine grinding is 20S, the time for coarse polishing is 60S, and the time for fine polishing is 60S.

[0057] The comparative polishing adopts an arc-shaped long tail polishing track, such as Fig.10 As shown, it is specifically an arc-shaped (1C / 4) long tail, polished twice, and the polishing time for both times is 20S. During the two polishings, the surface of the sample is completely in contact with the grinding disk, and the sample does not rotate during the contact process.

[0058] Figure 1 and Figure 2 This is a metallographic micrograph of the spheroidizing annealing sample of the bearing steel prepared in Example 1; the metallographic structure after optimizing the polishing method is displayed: the vectors in all directions of the sample are evenly distributed through a circular rotating trajectory, so that the roundness, size, and stacking of the granular pearlite structure can be fully displayed, and the temperature and time of the spheroidizing annealing process of the bearing steel can be evaluated more comprehensively.

[0059] Figure 3 and Figure 4 This is a metallographic micrograph of the spheroidizing annealing tissue sample of the bearing steel prepared in Comparative Example 1; as shown in the figure, after the sample is immersed in 4% nitric acid alcohol corrosion solution, part of the granular pearlite tissue morphology is inclined to the upper left corner, and the overall morphology of the spheroidal pearlite cannot be fully displayed. The roundness, size, and stacking of the spheroidal pearlite cannot be fully evaluated, and the temperature and time of the spheroidizing annealing process of the bearing steel cannot be fully evaluated.

Claims

1. An efficient preparation method for a bearing steel spheroidizing annealing structure sample, characterized in that: The method includes improving the sample grinding process, optimizing the manual polishing technique and finely controlling the grinding speed; the grinding process includes rough grinding, fine grinding, rough polishing and fine polishing; the manual polishing technique is fine polishing using a circular polishing trajectory for three times; the finely controlling the grinding speed is to set the grinding disc rotation speed to 100-200rpm.

2. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 1, characterized in that: The grinding particle size of the coarse grinding is 42#, the grinding particle size of the fine grinding is 320#, the grinding particle size of the rough polishing is 800#, and the grinding particle size of the fine polishing is W5.

3. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 1 or 2, characterized in that: During the rough polishing and fine polishing, the grinding disc rotates in a clockwise direction.

4. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 3, characterized in that: During the first and second polishing of fine polishing, hold the sample and make circular motion on the grinding disc along the circular polishing trajectory. During the movement, tilt the sample appropriately so that the surface of the sample briefly contacts the grinding disc locally, and at the same time, rotate the sample in the clockwise direction.

5. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 4, characterized in that: During the first polishing of fine polishing, the upper part of the sample surface is temporarily in contact with the grinding disc, and the angle of the sample rotation in the clockwise direction is 60 to 90 degrees.

6. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 5, characterized in that: During the second polishing of fine polishing, the lower part of the sample surface is partially and briefly in contact with the grinding disc, and the angle of the sample rotation in the clockwise direction is 60 to 90 degrees.

7. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 6, characterized in that: During the third polishing of fine polishing, hold the sample and make circular motion on the grinding disc along the circular polishing trajectory so that the entire surface of the sample contacts the grinding disc. The sample does not rotate during the contact process.

8. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 7, characterized in that: The grinding disc rotation speed was set to 150 rpm.

9. The method for efficiently preparing a spheroidizing annealing microstructure sample of a bearing steel according to claim 8, characterized in that: The time for the coarse grinding is 10 to 20 seconds, the time for the fine grinding is 10 to 20 seconds, the time for the rough polishing is 30 to 60 seconds, the time for the first polishing is 10 to 20 seconds, the time for the second polishing is 10 to 20 seconds, and the time for the third polishing is 10 to 20 seconds.

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