Method for determining residual stress of bearing ring curved surface

Abstract

The present application relates to a kind of bearing ring curved surface residual stress determination method, belong to bearing part residual stress detection technical field.The bearing ring curved surface residual stress determination method of the present application, comprising the following steps: according to the shrinkage of the measured surface of the measured bearing ring before and after heat treatment in circumferential direction, calculate strain value;Based on the corresponding relationship between stress and strain, calculate and determine the residual stress of the measured surface;The material of the measured bearing ring is GCr15;The temperature of the heat treatment is 500 DEG C;Martensite microstructure of the measured bearing ring is 2~3 grade, and the Rockwell hardness of the measured bearing ring is 58~62.The bearing ring curved surface residual stress determination method of the present application has the advantages of simple operation and high accuracy of result.

Description

TECHNICAL FIELD

[0001] The application relates to a bearing ring curved surface residual stress determination method and belongs to the technical field of bearing part residual stress detection. BACKGROUND

[0002] It is known that the detection and evaluation of bearing part residual stress has been a problem concerned by the bearing industry. GCr15 material is widely used in bearing manufacturing due to high and uniform hardness after quenching and tempering, high wear resistance, high anti-fatigue strength, good hot workability and good comprehensive performance. With the continuous improvement of bearing processing capacity and level, people pay more and more attention to the related common technical problems of bearings made of GCr15 material, especially the processing control and evaluation of bearing working surface residual stress.

[0003] At present, residual stress measurement methods are mainly divided into two categories: mechanical method and non-destructive testing method. Most of the non-destructive testing methods belong to physical methods, and the basic principle is as follows: based on the basic premise that residual stress will cause a change in a certain physical quantity of the material, the relationship between the physical quantity and the residual stress is established, and the residual stress is calculated by measuring the physical quantity. The destructive testing method is to remove a part of the measured workpiece by mechanical processing, and the local residual stress is released to produce corresponding strain and displacement. By using the corresponding strain and displacement, the residual stress can be determined, and the original residual stress of the workpiece can be calculated according to the related mechanical principle.

[0004] In the actual detection process of bearing processing enterprises, considering the accuracy and reliability of the detection results, the surface residual stress detection usually adopts the X-ray diffraction method, which is more accurate and is a method recognized by the industry. However, due to the high price of X-ray diffraction equipment, the detection area and depth are small, and it is difficult to measure the stress of the inner and outer surfaces of small-sized parts and the working surface with large curvature. SUMMARY

[0005] The application aims to provide a bearing ring curved surface residual stress determination method, which can solve the problem of high price in the detection of bearing ring curved surface residual stress by using the X-ray diffraction method.

[0006] In order to achieve the above purpose, the technical scheme of the bearing ring curved surface residual stress determination method adopted by the application is as follows:

[0007] The application discloses a method for determining the residual stress of a bearing ring curved surface, and comprises the following steps: calculating the strain value according to the circumferential direction expansion and contraction amount of the to-be-measured curved surface of a to-be-measured bearing ring before and after heat treatment; and determining the residual stress of the to-be-measured curved surface based on the corresponding relationship between stress and strain. The material of the to-be-measured bearing ring is GCr15, the temperature of the heat treatment is 500 DEG C, the martensite microstructure of the to-be-measured bearing ring is 2-3 grade, and the Rockwell hardness of the to-be-measured bearing ring is 58-62. The calculation formula of the residual stress is as follows:

[0008]

[0009] Wherein, sigma is the residual stress, the unit is MPa; epsilon is the strain value; E is the elastic modulus, the unit is MPa.

[0010] The method for determining the residual stress of the bearing ring curved surface has the advantages of simple operation and high result accuracy.

[0011] Preferably, the roughness Ra of the to-be-measured curved surface is less than or equal to 6.4.

[0012] Preferably, the roughness Ra of the to-be-measured curved surface is less than or equal to 1.6.

[0013] Preferably, the heat treatment time is 2h.

[0014] Preferably, the to-be-measured curved surface is the inner diameter, the outer diameter or the raceway of the to-be-measured bearing ring.

[0015] Preferably, the to-be-measured curved surface is the inner diameter of the to-be-measured bearing ring, and the circumferential direction expansion and contraction amount is determined by measuring the diameter change of the inner diameter; the to-be-measured curved surface is the outer diameter of the to-be-measured bearing ring, and the circumferential direction expansion and contraction amount is determined by measuring the diameter change of the outer diameter; the to-be-measured curved surface is the raceway of the to-be-measured bearing ring, and the circumferential direction expansion and contraction amount is determined by measuring the diameter change of the raceway.

[0016] Preferably, the calculation formula of the strain value is as follows:

[0017]

[0018] Wherein, is the size parameter of the to-be-measured curved surface of the to-be-measured bearing ring before heat treatment, the unit is mm; is the size parameter of the to-be-measured curved surface of the to-be-measured bearing ring after heat treatment, the unit is mm; epsilon is the strain value.

[0019] Compared with the prior art, the beneficial effects of the present application are as follows: the bearing ring with a material of GCr15 is subjected to heat treatment at 500 DEG C, and the martensite microstructure of the bearing ring before heat treatment is controlled to be 2-3 levels, and the Rockwell hardness is 58-62, and the relationship between the strain and stress obtained by the circumferential direction expansion and contraction amount of the to-be-tested curved surface of the bearing ring before and after heat treatment can be more accurately determined to determine the residual stress of the to-be-tested curved surface of the bearing ring. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The appearance picture of the to-be-tested bearing ring in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0021] The determination method of the residual stress of the curved surface of the bearing ring of the present application is an opening invention. In view of the problems that the X-ray diffraction method is expensive and difficult to measure the inner and outer surfaces and the working surface with large curvature of the small-sized parts at present, the present application detects the strain values of the to-be-tested curved surface before and after heat treatment, and calculates and determines the residual stress of the to-be-tested curved surface by using the corresponding relationship between the stress and the strain.

[0022] The technical solutions of the present application are described in detail in combination with specific embodiments.

[0023] Embodiment 1

[0024] The determination method of the residual stress of the curved surface of the bearing ring of the present embodiment takes the bearing ring with a material of GCr15 as shown in Figure 1 the to-be-tested bearing ring, and the bearing ring includes a heat treatment step of quenching and tempering in the processing, and the bearing ring as a whole has no abnormal shape such as oval deformation and warping, and the outer diameter of the bearing ring is taken as the to-be-tested curved surface, and specifically includes the following steps:

[0025] (1) According to the method in the standard GB / T34891-2017, the microstructure of the to-be-tested bearing ring is analyzed and the martensite microstructure grade of the to-be-tested bearing ring is determined; according to the method in the standard GB / T230.1-2009, the Rockwell hardness HRC of the to-be-tested bearing ring is tested; and according to the method in the standard JB / T 7051-2006, the roughness of the to-be-tested curved surface of the to-be-tested bearing ring is tested; the test results are as follows: the martensite microstructure grade of the to-be-tested bearing ring is 3, the Rockwell hardness is 61.7HRC, and the roughness Ra of the to-be-tested curved surface is 0.18 μm.

[0026] (2) The measurement accuracy of the five-axis coordinate measuring machine and the temperature accuracy of the box-type resistance furnace are calibrated to ensure the stability and accuracy of the measurement results. The measurement accuracy of the five-axis coordinate measuring machine is 1.0 μm, and the temperature accuracy of the box-type resistance furnace is 0.1℃. The test temperature range of the box-type resistance furnace is room temperature to 1000℃, and the box-type resistance furnace is equipped with a temperature sensor.

[0027] (3) The diameter of the outer diameter of the bearing ring to be measured is detected using the five-axis coordinate measuring machine , and the position of the initial origin O of the measurement is determined, and the relevant parameters of the instrument during detection are recorded. The measurement result of the diameter of the outer diameter measured in this embodiment is 110.0214 mm.

[0028] (4) The bearing ring to be measured is placed horizontally in the central position of the box-type resistance furnace, and the bearing ring to be measured is heated to 500℃ with the furnace, and the temperature is maintained for 2h. After the temperature maintaining is completed, the bearing ring to be measured is cooled to room temperature with the furnace.

[0029] (5) The bearing ring to be measured cooled with the furnace is placed on the five-axis coordinate measuring machine again, and the diameter of the outer diameter of the bearing ring to be measured is measured under the conditions of the instrument related parameters and the initial origin O position in step (3) . The measurement result of the diameter of the outer diameter measured in this embodiment is 110.2128 mm.

[0030] (6) The residual stress is calculated using the detection results of the diameters of the outer diameters of the bearing ring to be measured before and after heat treatment; the calculation formula is as follows:

[0031]

[0032]

[0033] In the formula, D1 is the diameter of the outer diameter of the bearing ring to be measured before heat treatment, in mm; D2 is the diameter of the outer diameter of the bearing ring to be measured after heat treatment, in mm; ε is the strain value of the bearing ring to be measured before and after heat treatment; E is the elastic modulus, in MPa; σ is the residual stress, in MPa. In this embodiment, the elastic modulus E = 207 GPa.

[0034] Example 2

[0035] The method for determining the residual stress of the bearing ring curved surface in this embodiment takes a bearing ring with a material of GCr15 as the bearing ring to be measured. The bearing ring includes a heat treatment step of quenching and tempering during processing, and the bearing ring as a whole has no abnormal shape such as oval deformation and warping. The raceway of the bearing ring is taken as the curved surface to be measured, and the method specifically includes the following steps: ​​

[0036] (1) According to the method in standard GB / T34891-2017, the microstructure of the bearing ring to be tested is analyzed and the martensite microstructure grade of the bearing ring to be tested is determined; according to the method in standard GB / T230.1-2009, the Rockwell hardness HRC of the bearing ring to be tested is tested; according to the method in standard JB / T 7051-2006, the roughness of the test surface of the bearing ring to be tested is tested; the test results are as follows: the martensite microstructure grade of the bearing ring to be tested is 3, the Rockwell hardness is 61.5HRC, and the roughness Ra of the test surface is 0.18μm.

[0037] (2) The measurement accuracy of the five-axis coordinate measuring machine and the temperature accuracy of the box-type resistance furnace are calibrated to ensure the stability and accuracy of the measurement results, the measurement accuracy of the five-axis coordinate measuring machine is 1.0μm, the temperature accuracy of the box-type resistance furnace is 0.1℃, the test temperature range of the box-type resistance furnace is room temperature to 1000℃, and the box-type resistance furnace is equipped with a temperature sensor.

[0038] (3) The diameter of the raceway of the bearing ring to be tested is detected using the five-axis coordinate measuring machine , and the position of the initial origin O of measurement is determined, and the relevant parameters of the instrument during detection are recorded. The measurement result of the diameter of the raceway measured in this embodiment is 110.0956mm.

[0039] (4) The bearing ring to be tested is placed horizontally at the central position of the box-type resistance furnace, and the bearing ring to be tested is heated to 500℃ with the furnace, and the temperature is kept for 2h, and after the temperature keeping is finished, the bearing ring to be tested is cooled to room temperature with the furnace.

[0040] (5) The bearing ring to be tested cooled with the furnace is placed on the five-axis coordinate measuring machine again, and the diameter of the raceway of the bearing ring to be tested is measured . The measurement result of the diameter of the raceway measured in this embodiment is 110.2797mm.

[0041] (6) The residual stress is calculated by using the detection results of the raceway size parameters of the bearing ring to be tested before and after heat treatment; the calculation formula is as follows:

[0042]

[0043]

[0044] In the formula, D1 is the diameter of the outer diameter of the bearing ring to be tested before heat treatment, in mm; ​​D is the diameter of the outer diameter of the bearing ring to be measured after heat treatment, in mm; ε is the strain value of the bearing ring to be measured before and after heat treatment; E is the elastic modulus, in MPa; and σ is the residual stress, in MPa. In this embodiment, the elastic modulus E = 207 GPa.

[0045] Example 3

[0046] The difference between the method for determining the residual stress of the curved surface of the bearing ring of this embodiment and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of this embodiment, the roughness Ra of the curved surface to be measured is 1.6 μm.

[0047] Example 4

[0048] The difference between the method for determining the residual stress of the curved surface of the bearing ring of this embodiment and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of this embodiment, the roughness Ra of the curved surface to be measured is 6.4 μm.

[0049] Example 5

[0050] The difference between the method for determining the residual stress of the curved surface of the bearing ring of this embodiment and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of this embodiment, the microstructure grade of the bearing ring to be measured is Grade 2.

[0051] Example 6

[0052] The difference between the method for determining the residual stress of the curved surface of the bearing ring of this embodiment and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of this embodiment, the Rockwell hardness is 58 HRC.

[0053] Comparative Example 1

[0054] The method for determining the residual stress of the curved surface of the bearing ring of this comparative example uses a bearing ring made of GCr15 as the bearing ring to be measured. The bearing ring includes a heat treatment step of quenching and tempering when being processed. The bearing ring as a whole has no abnormal shape such as oval deformation or warping. The inner diameter of the bearing ring is used as the curved surface to be measured. The method specifically includes the following steps:

[0055] (1) According to the method in standard GB / T34891-2017, the microstructure of the bearing ring to be tested is analyzed and the martensite microstructure grade of the bearing ring to be tested is determined; according to the method in standard GB / T230.1-2009, the Rockwell hardness HRC of the bearing ring to be tested is tested; according to the method in standard JB / T 7051-2006, the roughness of the test surface of the bearing ring to be tested is tested; the test results are as follows: the martensite microstructure grade of the bearing ring to be tested is 3, the Rockwell hardness is 62.1HRC, and the roughness Ra of the test surface is 0.17μm.

[0056] (2) The measurement accuracy of the five-axis coordinate measuring machine and the temperature accuracy of the box resistance furnace are calibrated to ensure the stability and accuracy of the measurement results, the measurement accuracy of the five-axis coordinate measuring machine is 1.0μm, the temperature accuracy of the box resistance furnace is 0.1℃, the test temperature range of the box resistance furnace is room temperature to 1000℃, and the box resistance furnace is equipped with a temperature sensor.

[0057] (3) The diameter of the inner diameter of the bearing ring to be tested is detected by using the five-axis coordinate measuring machine , and the position of the initial origin O of measurement is determined, and the relevant parameters of the instrument during detection are recorded. The measurement result of the diameter of the inner diameter measured in the pair of examples is 110.0113mm.

[0058] (4) The bearing ring to be tested is placed horizontally in the central position of the box resistance furnace, and the bearing ring to be tested is heated to 500℃ with the furnace, and the temperature is kept for 2h, and after the temperature keeping is finished, the bearing ring to be tested is cooled to room temperature with the furnace.

[0059] (5) The bearing ring to be tested cooled with the furnace is placed on the five-axis coordinate measuring machine again, and the diameter of the inner diameter of the bearing ring to be tested is measured . The measurement result of the diameter of the inner diameter measured in the pair of examples is 110.1149mm.

[0060] (6) The residual stress is calculated by using the inner diameter size parameter detection results of the bearing ring to be tested before and after heat treatment; the calculation formula is as follows:

[0061]

[0062]

[0063] In the formula, is the diameter of the outer diameter of the bearing ring to be tested before heat treatment, in mm; D is the diameter of the outer diameter of the bearing ring to be measured after heat treatment, in mm; ε is the strain value of the bearing ring to be measured before and after heat treatment; E is the elastic modulus, in MPa; and σ is the residual stress, in MPa. In the present comparative example, the elastic modulus E = 207 GPa.

[0064] Comparative Example 2

[0065] The difference between the method for determining the residual stress of the curved surface of the bearing ring of the present comparative example and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of the present comparative example, the microstructure grade of the bearing ring to be measured is Grade 4.

[0066] Comparative Example 3

[0067] The difference between the method for determining the residual stress of the curved surface of the bearing ring of the present comparative example and the method for determining the residual stress of the curved surface of the bearing ring of Example 1 is that, in step (1) of the method for determining the residual stress of the curved surface of the bearing ring of the present comparative example, the Rockwell hardness is 63 HRC.

[0068] In order to evaluate the error between the residual stress determined in each example and each comparative example and the actual value of the residual stress, the residual stress of the curved surface to be measured of the bearing ring to be measured in each example and each comparative example was determined according to the standard “GB / T 7704-2017 Nondestructive Testing X-ray Stress Measurement Method”, and the actual determination result of the residual stress was obtained. The calculated value of the residual stress of each example and each comparative example and the actual determination result are summarized in Table 1. The error percentage in Table 1 = |calculated value of residual stress-actual determination result of residual stress| / actual determination result of residual stress x 100%.

[0069] Table 1 Determination results and actual determination results of residual stress in each example and each comparative example

[0070] Determination method Residual stress calculated value (MPa) Residual stress actual measurement result (MPa) Error percentage (%) Example 1 -360.1 -370.3 2.75 Example 2 -346.1 -352.7 1.87 Example 3 -323.5 -332.3 2.65 Example 4 -317.7 -329.8 3.67 Example 5 -297.8 -306.2 2.74 Example 6 -316.5 -309.5 2.26 Comparative Example 1 -194.9 -211.3 7.76 Comparative Example 2 -285.4 -339.4 15.91 Comparative Example 3 -327.2 -357.1 8.37

[0071] As shown in Table 1, by changing the initial conditions such as the surface roughness, microstructure grade, and surface hardness of the sample to be measured, the calculated residual stress value of the curved surface obtained by using the method of the present application, and the actual determination result of the surface residual stress by X-ray diffraction method, it can be seen that the change of the surface roughness of the sample to be measured has little effect on the measurement result of the residual stress, and when the microstructure grade and the surface hardness of the sample to be measured tend to the upper limit, the deviation between the calculated stress value and the actual determination result by diffraction method is larger; therefore, the martensite microstructure of the bearing ring to be measured is Grade 2-3, the Rockwell hardness of the bearing ring to be measured is 58-62, and the roughness Ra of the curved surface to be measured is ≤6.4 μm, more preferably the roughness Ra is ≤1.6 μm.

Claims

1. A method for determining the residual stresses of a bearing ring curved surface, the bearing ring comprising a quenching and tempering heat treatment step when machined, characterized in that, The method comprises the following steps: According to the circumferential direction expansion and contraction amount of the to-be-tested curved surface of the to-be-tested bearing ring before and after 500 DEG C heat preservation for 2h, the strain value is calculated; Based on the corresponding relationship between stress and strain, the residual stress of the to-be-tested curved surface is calculated and determined; the material of the to-be-tested bearing ring is GCr15; the martensite microstructure of the to-be-tested bearing ring is 2-3 levels, the Rockwell hardness of the to-be-tested bearing ring is 58-62, and the roughness Ra of the to-be-tested curved surface is less than or equal to 6.4; the to-be-tested curved surface is the inner diameter, the outer diameter or the raceway of the to-be-tested bearing ring, and the corresponding circumferential direction expansion and contraction amount is determined by measuring the diameter change of the inner diameter, the outer diameter or the raceway; the calculation formula of the residual stress is as follows: Wherein, sigma is the residual stress, the unit is MPa; epsilon is the strain value; E is the elastic modulus, the unit is Mpa; The calculation formula of the strain value is: wherein, is the size parameter of the measured surface of the bearing ring before heat treatment, in mm; is the size parameter of the measured surface of the bearing ring after heat treatment, in mm; and ε is the strain value.

2. The method of claim 1, wherein the step of determining the residual stress of the curved surface of the bearing ring is performed by the steps of: The roughness Ra of the to-be-tested curved surface is less than or equal to 1.

6. ​

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