Experimental method for exfoliation and reproduction of white tissue and application of experimental method

Abstract

The invention relates to a white tissue exfoliation reproduction experimental method and application thereof. The method comprises the following steps: hydrotreating a bearing test piece to obtain a hydrogen-embedded test piece; fixing the test piece in a reciprocating motion device, applying pressure in the direction perpendicular to the reciprocating motion, starting the reciprocating motion device, and enabling the test piece pre-buried with hydrogen to do reciprocating motion under the action of the pressure until white tissues are peeled off. By using the method provided by the invention, the occurrence time of white tissue peeling can be greatly reduced. For example, a bearing used for new energy motor equipment and high-carbon chromium bearing steel treated by an oxidation blackening process can be simulated within about 90 hours by using the experimental method disclosed by the invention, which is equivalent to 320 hours of the traditional test, and the time of the bearing exceeds 5 years in actual use. The method provided by the invention is simple, convenient and cheap, has higher efficiency, can be used for simulating the test of white tissue peeling, and realizes the performance test of white tissue peeling and bearing detection during bearing production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bearing detection, and particularly relates to a white structure spalling reproduction experimental method and application thereof. BACKGROUND

[0002] White etching cracks (WEC) is a kind of fatigue failure, which is different from subsurface origin type fatigue failure. When WEC failure occurs, white structure and cracks preferentially occur at original grain boundaries and are generated in deeper near-surface layer, which is more harmful. WEC failure will greatly reduce the bearing life, and the bearing life distribution is more concentrated, and the failure time is only 1 / 10 of the designed calculated life.

[0003] In the wind power industry, the variable pitch bearing is a key component of the wind turbine generator set, responsible for adjusting the angle of the wind turbine blades to adapt to different wind speed conditions, thereby optimizing the efficiency of wind energy capture and utilization. However, the variable pitch bearing may encounter white spalling problems during operation, which not only affects its performance, but also may cause more serious failures. In new energy vehicles, bearings may also encounter similar problems.

[0004] For these key component bearings, such as motor bearings, their performance against white spalling needs to be tested during research and development and production. In the prior art, a conventional bearing rotation method is usually used for testing, such as using an FE-8 bearing life tester for testing. This device is expensive, costing 2 million yuan per unit, and requires large bearings, and the cost of a test also needs to be tens of thousands of yuan. More importantly, the above-mentioned testing method is time-consuming, and the bearing experiment takes more than 300 hours.

[0005] The present application uses a simple reciprocating test device, which is inexpensive, with a device cost of several ten thousand yuan, and a test cost of only a few hundred yuan, to simulate the conventional bearing rotation test method and reproduce white structure spalling (WEC). SUMMARY

[0006] The purpose of the present application is to provide a white structure spalling reproduction experimental method to solve the problems in the prior art.

[0007] The purpose of the present application can be achieved by the following scheme: The present application provides a white structure spalling reproduction experimental method, comprising the following steps: S1, hydrogenating a bearing test piece to obtain a pre-embedded hydrogen test piece; S2, fixing the pre-embedded hydrogen test piece in a reciprocating motion device, applying pressure in a direction perpendicular to the reciprocating motion, starting the reciprocating motion device, and making the pre-embedded hydrogen test piece reciprocate under the action of the pressure until white structure spalling occurs.

[0008] In step S1, the material of the bearing test piece is one of stainless steel, carburizing steel, heat-resistant steel, high-carbon chromium bearing steel treated by oxidation and blackening process, preferably high-carbon chromium bearing steel AISI 52100.

[0009] In the field of wind power and new energy vehicles, in order to improve the hardness, wear resistance and corrosion resistance of the bearing surface, the oxidation and blackening process is usually used to form a dense black film.

[0010] Oxidation and blackening process: immerse the bearing in an aqueous solution of alkaline salt (sodium hydroxide, sodium nitrite, etc.) at 130-150 °C for 10-20 min to form a 1-2 μm deep black surface layer (FeO, Fe2O3 and Fe3O4 mixture). Black oxide is a surface treatment formed by chemical reaction of the surface layer of bearing steel. When the part is immersed in an aqueous solution of alkaline salt, the reaction between iron in the iron alloy and the reagent produces an oxide layer on the outer layer of the bearing part, consisting of FeO, Fe2O3 mixture and generated Fe3O4, finally forming a deep black surface layer with a thickness of about 1-2 μm.

[0011] In step S1, hydrogenation treatment is soaking in aqueous ammonium thiocyanate solution or electrolytic hydrogen charging. The present application makes hydrogen exist in the bearing test piece through hydrogenation treatment.

[0012] Soaking in aqueous ammonium thiocyanate solution: immerse the bearing test piece in aqueous ammonium thiocyanate solution. The concentration of aqueous ammonium thiocyanate solution is 20wt%-40wt%, preferably 35wt%-40wt%. The soaking temperature is 45-55℃, and the soaking time is 48h-72h.

[0013] Electrolytic hydrogen charging: the bearing test piece is used as the cathode, platinum sheet is used as the anode, and they are placed in the electrolyte and subjected to electrolysis by passing direct current. The electrolyte includes sulfuric acid, thiourea and NaAsO2. The concentration of sulfuric acid in the electrolyte is 0.1-1 mol / L, the content of thiourea is 0.1-0.5 g / L, and the content of NaAsO2 is 0.01-0.05 g / L. The voltage of electrolysis is 1-10 V, and the time of electrolysis is 1-48 h.

[0014] In step S2, the reciprocating device includes a solid device that can fasten the bearing test piece, a motor that drives the solid device and the bearing test piece to reciprocate, and a pressure device that continuously applies pressure to the bearing test piece. The contact between the pressure device and the base part of the bearing test piece is spherical.

[0015] In step S2, the applied pressure is 40-60 N, preferably 50-60 N.

[0016] In step S2, the stroke of reciprocating motion is 0.8-1.5 mm, preferably 0.9-1.1 mm.

[0017] The frequency of the reciprocating motion in step S2 is 3-20 Hz, preferably 3-15 Hz, and more preferably 4-6 Hz.

[0018] In step S2, the groove of the reciprocating motion device is filled with base oil, lubricating oil or lubricating grease. The base oil is PAO.

[0019] The application also provides an application of the experimental method for reproducing the white tissue peeling in bearing detection.

[0020] The application also provides a bearing detection method for the white tissue peeling phenomenon, comprising the following steps: setting parameters by the experimental method, detecting qualified bearings, obtaining the time T h of the white tissue peeling, and detecting bearings of the same material but not subjected to detection by using the same parameters, and the time of the white tissue peeling is greater than (T-A) h, and the bearing is qualified.

[0021] A is 3-5.

[0022] The time T h can be tested for multiple times, preferably 3-5 times, and the average value is taken.

[0023] The qualified bearing is an actually used qualified bearing or a bearing detected by a conventional bearing rotation method. The conventional bearing rotation method is that a hydrogen-treated bearing is loaded on an FE-8 bearing life tester for detection. The parameters are that the bearing load is 6 KN, and the rotation speed is 1960 r / min.

[0024] Compared with the prior art, the application has the following beneficial effects: By using the method of the application, the time of the white tissue peeling is about 90 h, which can simulate the time of 320 h of the conventional test, and the time of the bearing is more than 5 years in actual use. The method of the application is simple and inexpensive, and has higher efficiency, and can be used for simulating the test of the white tissue peeling and realizing the performance test of the white tissue peeling in bearing production. BRIEF DESCRIPTION OF DRAWINGS

[0025] Other features, objects and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings: Figure 1 A photo of an MTF4000 reciprocating tester used in the experiment of the application; Figure 2 A photo of the upper part (left) and the lower part (right) of the MTF4000 reciprocating tester used in the experiment of the application; Figure 3 A bearing test piece before hydrogen embedding in Example 1; Figure 4 A bearing test piece after hydrogen embedding in Example 1; Figure 5 Schematic diagram of 1mm stroke of the bearing test piece of Example 1 for reciprocating rear surface; Figure 6 Metallographic analysis micrograph of white tissue cracks appearing on the bearing test piece of Example 1. DETAILED DESCRIPTION

[0026] The application will be described in detail below with reference to the drawings and specific examples. The following examples are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are provided, which will help those skilled in the art to further understand the application. It should be pointed out that the protection scope of the application is not limited to the following examples, and several adjustments and improvements made on the premise of the concept of the application all belong to the protection scope of the application.

[0027] The reciprocating decoration used in the application is a conventional FE-8 reciprocating tester, as shown in Figure 1 , Figure 2 , which includes a firm device for fastening the bearing test piece, a motor for driving the firm device and the bearing test piece to reciprocate, and a pressure device for continuously applying pressure to the bearing test piece. The pressure applied by the pressure device is perpendicular to the direction of reciprocation, and the contact between the pressure device and the base part of the bearing test piece is spherical.

[0028] Example 1 This example is directed to experimental conditions for reproducing white tissue peeling. The bearing test piece used in this example is a bearing for new energy motor equipment, which is a high-carbon chromium bearing steel (AISI 52100) treated by oxidation and blackening process. In actual use, white tissue peeling appeared after 5 years of actual use.

[0029] (1) The steps of the experimental method are as follows: S1, take the existing bearing test piece for new energy motor bearing equipment, as shown in Figure 3 , immerse it in a 40wt% ammonium thiocyanate aqueous solution with a temperature of 50℃ for 48h, and perform hydrogenation treatment to make hydrogen exist in the bearing test piece, to obtain a pre-embedded hydrogen test piece, as shown in Figure 4 ; S2, test using MTF4000 reciprocating tester, fix the pre-embedded hydrogen test piece in the reciprocating device, and apply a pressure of 50N perpendicular to the direction of reciprocation, start the reciprocating device, the stroke of reciprocation is 1mm, the frequency is 5Hz, make the pre-embedded hydrogen test piece reciprocate under the action of pressure, run for 92h, the number of cycles is 4.968*10 6 , the surface (1mm stroke) of the bearing test piece is as shown in Figure 5 , and the white tissue cracks appearing on the bearing test piece are as shown in Figure 6 .

[0030] (2) Without pre-embedded hydrogen treatment: Take the same bearing test piece, without pre-embedded hydrogen treatment, and the same as step (1), the same test is carried out, and white tissue peeling occurs at 500h.

[0031] (3) Conventional bearing rotation method: The same as step (1), the bearing is also subjected to hydrogen treatment, and the conventional bearing rotation (bearing life tester) method is used for testing, specifically, the hydrogen-treated bearing is loaded on the FE-8 bearing life tester, the bearing load is 6KN, and the rotation speed is 1960r / min. This method finally appears white tissue peeling after 320h of testing.

[0032] Using the above methods in (1) and (3), experiments are carried out on qualified bearings 1-3, and the same experiments are carried out on unqualified bearings 4-5, and the results are shown in Table 1 below: Table 1

[0033] Conclusion: Using the method of the present application, the time of white tissue peeling occurs is about 90h, which can simulate the time of 320h of conventional testing. The detection time of the present application is about 28% of the time of conventional testing. In actual continuous use, the bearing is actually used for about 5 years, and white tissue peeling occurs. For unqualified bearings, the detection time is also about 28% of the time of conventional testing. It can be seen that for this type of bearing, the detection time of the present application is >88h, and the bearing is qualified. The method of the present application is simple, inexpensive and more efficient, and can be used for testing of white tissue peeling. The performance test of white tissue peeling during bearing material research and development and production is realized.

[0034] Example 2 This example is a white tissue peeling reproduction experiment, and the steps are as follows: S1, take the same bearing test piece as in Example 1, immerse it in a 40wt% ammonium thiocyanate aqueous solution at a temperature of 50℃ for 48h, and carry out hydrogen treatment to make hydrogen exist in the bearing test piece, to obtain a pre-embedded hydrogen test piece; S2, use MTF4000 reciprocating tester for testing, fix the pre-embedded hydrogen test piece in the reciprocating device, and apply a pressure of 50N perpendicular to the reciprocating direction, start the reciprocating device, the reciprocating stroke is 1mm, and the frequency is 15Hz, so that the pre-embedded hydrogen test piece is subjected to reciprocating motion under the action of pressure, and white tissue peeling occurs at 72h.

[0035] Conclusion: It can be seen that the frequency of reciprocating motion is increased, and the experimental time is shortened, but the frequency is higher, and the service life of the device is shortened.

[0036] Example 3 The bearing test piece used in this example is a high-strength alloy steel (GCr15) treated by oxidation blackening process for a wind power main bearing. The experimental steps are the same as those in Example 1, and the experimental results of bearing test pieces 1-3 are shown in Table 2. Table 2

[0037] Example 4 This example is a white tissue peeling experiment, and the steps are basically the same as those in Example 1, with the only difference being that the 50N pressure is adjusted to 20N, 40N, 60N and 80N respectively.

[0038] Under the action of 20N pressure, white tissue peeling occurs at 150h.

[0039] Under the action of 40N pressure, white tissue peeling occurs at 110h.

[0040] Under the action of 60N pressure, white tissue peeling occurs at 65h.

[0041] Under the action of 80N pressure, white tissue peeling occurs at 62h.

[0042] Conclusion: It can be seen that further increasing the pressure does not significantly shorten the time, and selecting too large pressure will cause the service life of the device to be shortened, so the pressure applied by the present application is selected to be 40-60N.

[0043] Example 5 The bearing test piece (the same as in Example 1) is used as the cathode, and the platinum sheet is used as the anode, which is placed in the electrolyte (0.5mol / L dilute sulfuric acid, 0.2g / L thiourea, 0.02g / L NaAsO2), and direct current (voltage 3V) is passed for 5h.

[0044] The experimental steps are the same as those in Example 1, and the experimental results are shown in Table 3. Table 3

[0045] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or modifications within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. An experimental method for white tissue exfoliation reproduction, characterized by, The method comprises the following steps: S1, hydrogenating the bearing test piece to obtain a hydrogen-embedded test piece; S2, fixing the hydrogen-embedded test piece in a reciprocating device, applying pressure in a direction perpendicular to the reciprocating direction, starting the reciprocating device, and making the hydrogen-embedded test piece reciprocate under the pressure until white flaking occurs.

2. The experimental method of white tissue exfoliation reproduction according to claim 1, characterized in that, In step S1, the bearing test piece is one of stainless steel, carburizing steel, heat-resistant steel, and high-carbon chromium bearing steel treated by an oxidation and blackening process.

3. The experimental method for white tissue exfoliation reproduction according to claim 1, characterized in that, In step S1, the hydrogenation treatment is soaking in an ammonium thiocyanate aqueous solution or electrolytic hydrogen charging.

4. The experimental method for white tissue exfoliation reproduction according to claim 3, characterized in that, The soaking in the ammonium thiocyanate aqueous solution is soaking the bearing test piece in the ammonium thiocyanate aqueous solution; the concentration of the ammonium thiocyanate aqueous solution is 20wt%-40wt%; the soaking temperature is 45-55℃, and the soaking time is 48h-72h; And / or, the electrolytic hydrogen charging is placing the bearing test piece as a cathode and a platinum sheet as an anode in an electrolyte and electrolyzing by passing direct current; the electrolyte comprises 0.1-1mol / L sulfuric acid, 0.1-0.5g / L thiocyanic acid, and 0.01-0.05g / L NaAsO2.

5. The experimental method for white tissue exfoliation reproduction according to claim 1, characterized in that, In step S2, the reciprocating device comprises a firm device capable of fastening the bearing test piece, a motor for driving the firm device and the bearing test piece to reciprocate, and a pressure device for continuously applying pressure to the bearing test piece.

6. The experimental method of white tissue exfoliation reproduction according to claim 1, characterized in that, In step S2, the applied pressure is 40-60N.

7. The experimental method of white tissue exfoliation reproduction according to claim 1, characterized in that, In step S2, the reciprocating stroke is 0.8-1.5mm.

8. The experimental method of white tissue exfoliation reproduction according to claim 1, characterized in that, In step S2, the reciprocating frequency is 3-20Hz.

9. Application of the experimental method for reproducing white flaking according to claim 1 in bearing detection.

10. A bearing inspection method for white tissue shedding, characterized by, The method comprises the following steps: setting parameters by the experimental method according to claim 1, detecting qualified bearings, obtaining the time T h for white flaking to occur, and detecting bearings of the same material prepared but not detected by using the same parameters, and if the time for white flaking to occur is greater than (T-A) h, the bearing is qualified; A has a value range of 3-5.

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