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Research on the Reasons for the Spalling of the Outer Ring Raceway of Cylindrical Roller Bearings

by:JNSN     2022-09-26
1 Introduction Under certain conditions of use, rolling bearings often fail to reach their calculated life and cause early damage due to the influence of internal or external factors. Analysis of the early damage of rolling bearings, in which the peeling of the outer ring raceway of the bearing is one of the important factors. On the basis of studying the previous test results, this paper analyzes the reasons for the spalling of the outer ring raceway of cylindrical roller bearings, and proposes corresponding improvement measures. 2 Analysis of previous test results 2.1 Macroscopic analysis The outer ring of the bearing with raceway spalling is visually inspected. The spalling area is mostly distributed on one side of the raceway. In the spalling area, there are many thermal oxidative discoloration on the cylindrical surface of all rollers. It is a dark brown strip. On the roller side corresponding to the peeling of the raceway, the oxidation discoloration is more serious, and there are many indentations on the surface. The end face of the roller is worn and scratched, and the end face of the other side is close to the outer diameter. There is a slight oxidative discoloration ring, which is light brown. 2.2 Chemical composition analysis The chemical composition of the bearing outer ring is analyzed, and the results are shown in the following table: Table 1 Chemical composition/% c mn si cr s p 1.02 0.36 0.30 1.55 0.013 0.004 2.3 Hardness determination The hardness (hrc) test results are shown in Table 2: 2 The end face of the ferrule position (typing face) End face (non-typing face) Outer diameter and inner diameter (raceway face) Hardness value 61.8, 62.8, 62.3 62, 62, 62 60, 60.4, 60.4 60.2, 60.2, 60.1 2.4 Material quality analysis Table 3 Non-metallic inclusions (grade) Microstructure (grade) Oxide sulfide point deformation sulfide belt carbide liquified network carbide 1.5 2.0 0 1.5 0 1.5 At present, most of the foreign bearing materials use vacuum deoxidized steel , the oxygen content is stipulated below 15ppm, and only a few steel mills in my country can meet this requirement, and most other steel mills do not have the conditions, resulting in roller material organization greater than grade 4 and more cracks. In the material quality analysis, the non-metallic inclusions and microstructures were compared and analyzed using the yjz84 standard, and the sulfide impurity level in the ferrule exceeded the standard. The peeling outer ring was tested. At the peeling source, the metallographic sample was ground longitudinally at a distance of 0.5mm to 1mm from the source. It was observed that there were chain-like brittle inclusions within the range of 0.36mm-0.49mm from the peeling surface. These inclusions There are also micro-shock lines at the object. On the same metallographic sample, there are also chain-like brittle inclusions at a distance of about 0.8 mm from the peeled surface. The metallographic samples were ground longitudinally along the exfoliation source, and chain-like brittle inclusions were also observed at and near the source. There are tiny cracks between the inclusions at 0.3 mm from the peeled surface, and there are also chain-like brittle inclusions with a length of about 0.56 mm at 0.68 mm from the peeled surface. The above situation shows that there are many chain-like brittle inclusions on the surface of the outer raceway, some of which have exceeded the qualified level specified in the yjz84 standard. For the metallographic structure of the outer ring, the structure under the exfoliation surface at the exfoliation source is fine crystalline martensite + fine needle martensite + small granular carbide band distribution + retained austenite + a small amount of dots, needle-like Tropicana body. At the edge of the peeling place, although the surface of the raceway is not peeled off, there are parallel cracks under the surface. The microstructure of the surface of the raceway is fine crystalline martensite + fine needle martensite + fine granular carbide + retained austenite + Few points, needle-like troostite. The non-martensitic structure increases as it goes inward, but at 3 mm from the surface, the non-martensitic structure exceeds the specified acceptable level. 2.5 The heat treatment quality analysis of the ferrule shall be checked according to the heat treatment quality inspection standard of bearing parts. The quenched and tempered structure of the outer ring is shown in Table 4. Table 4 Depth from surface/mm Surface 1.0 2.0 3.0 Tissue level/level 6
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