Study on Causes of Exfoliation of Cylindrical Roller Bearing Outer Ring Raceway
In some conditions of use, rolling bearings often suffer from early damage due to internal or external factors that do not reach their calculated life. Analysis of the early damage of the rolling bearing, in which the bearing outer ring raceway spalling is one of the important factors. Based on the previous experimental results, this paper analyzes the causes of spalling of the outer ring raceway of cylindrical roller bearings and proposes corresponding improvement measures.
2 Analysis of past test results
1. Macroscopic analysis: The outer ring of the bearing where the raceway is peeled off is visually inspected. The spalling area is mostly distributed on one side of the raceway. In the spalling zone, many heated oxidative discoloration is dark brown on the cylindrical surface of all the rollers. The strip has a oxidative discoloration on the side of the roller corresponding to the flake stripping, and there are many indentations on the surface. The end face of the roller is worn and scratched, and the other end face is slightly near the outer diameter. The oxidized color changing ring is light brown.
2. Chemical composition analysis: Analyze the chemical composition of the outer ring of the bearing.
3. Hardness measurement: Hardness (HRC) measurement results.
Rim position end face (typed face) end face (non-type face) outer diameter inner diameter (raceway face) hardness value 61.8,62.8,62.362,62,6260,60.4,60.460.2,60.2,60.1
4, material quality analysis: non-metallic inclusions (grade) microstructure (grade) oxide sulfide point deformation sulfide with carbide liquid precipitation network carbide 1.52.001.501.5
At present, most of the foreign bearing materials use vacuum deoxidizing steel, the oxygen content is specified below 15ppm, and only some steel mills in China can meet this requirement. Most other steel mills do not have the conditions, resulting in roller material organization greater than 4, More cracks.
In the material quality analysis, non-metallic inclusions and microstructures were compared and analyzed using the YJZ84 standard, and the level of sulfide impurities in the ferrule exceeded the standard. The peeling outer ring was tested. At the stripping source, the metallographic sample was longitudinally ground from 0.5 mm to 1 mm from the source. It was observed that there were chain brittle inclusions in the range of 0.36 mm to 0.49 mm from the peeling surface. There are also fine lines in the object. On the same metallographic sample, chain-like brittle inclusions were also present at a distance of about 0.8 mm from the source. The metallographic sample was milled longitudinally along the stripping source, and chain brittle inclusions were also observed at and near the source. There was a microcrack between the inclusions at a distance of 0.3 mm from the peeling surface, and a chain-like brittle inclusion having a length of about 0.56 mm was also present at 0.68 mm from the peeling surface.
The above shows that there are more chain-like brittle inclusions on the surface of the outer raceway, and some have exceeded the qualification level specified in the YJZ84 standard.
For the metallographic structure of the outer ring, the structure under the surface of the exfoliation is finely crystallized martensite fine needle martensite fine granular carbide band-like distribution retained austenite a small amount of points, needle-shaped troostite. At the edge of the peeling point, although the surface of the raceway is not peeled off, there are parallel cracks under the surface. The structure of the raceway surface is fine crystal martensite fine needle martensite fine granular carbide retained austenite a small amount of needle, needle Quercus. As the interior penetrates, the non-martensite structure increases, but at 3 mm from the surface, the non-martensitic structure exceeds the specified qualification level.
5, the quality analysis of the ferrule heat treatment according to the bearing parts heat treatment quality inspection standards inspection, its outer ring quenching, tempering structure. Distance to surface depth / mm surface layer 1.02.03.0 organization level / level 6 <7 <99
From the perspective of macroscopic organization, the peeling is biased on the side of the raceway. This is mainly because the bearing is biased in the direction of use, causing uneven contact between the roller and the raceway, and an overload load is generated in a limited area of the bearing raceway, resulting in the bearing outer raceway. Early fatigue spalling. Therefore, during the installation of the rolling bearing, the inner casing should be prevented from tilting, so that the roller can be evenly contacted on the raceway to avoid local overload. At the same time, the bearing tilting should be avoided as much as possible during the use of the bearing. In addition, the cause of the force deviation is also related to the strength of the bearing housing and the shaft. Due to the poor strength of the support box or the shaft or the unreasonable fit between the parts, the rigidity is not enough, causing the inclination of the shaft to the outer casing, so that the stress is not distributed. In the market prospect of strong cylindrical wet machining system, experts pointed out that the wet machining machining chip removal and coolant purification system has just started in China, and most machining companies still lack understanding. If the system can be promoted and applied, it will have significant economic and social benefits, and the market prospect is very broad. It is understood that the wet machining system has been widely adopted in foreign industrialized countries, which has properly solved a series of problems in the metal cutting process and promoted the development of production. In China, single-machine cooling lubrication is currently used, and centralized cooling lubrication systems are used in only a few of the more advanced plants. According to the national plan, by 2010, the annual output of China's automobiles will reach 6 million, and it is necessary to carry out technical transformation of large engine plants. For this reason, it is necessary to promote the application of wet machining systems in some mass-produced machining factories and bearings, motorcycles, tractors and other industries. It can promote more and faster entry of China's mechanical products into the international market, generate foreign exchange for the country, and reduce imports of such equipment. The fifth phase of the mechanical engineer must predict the modern mold technology. Du Zhijun, Xu Cheng, Xin Xin, Feng Huawei, Tang Xiaohui, Zhong Gaoyan, Liu Feng, Dong Zhaolin, Ren Yubo, Cong Juan, Bai Chengzhi, Hong Liang, Zhang Youzhen, Li Jun, Han Chenghe. The development trend of pressure vessel structure large-scale automatic lathe tailstock automatic feed Drilling shaft hole short straight edge indexable scraping hob C616 lathe CNC conversion CNC lathe processing petroleum tubing thread using AutoCAD to draw parts catalogue group technology in CAD application locomotive axle grinding online measurement system development simple car Design and manufacture of brake drum boring machine Design measures to improve the structural strength of PTFE parts Rolling and its application Three examples of improved design of a pipeline filter Improved sealing device to solve the outer raceway of oil cylinder oil leakage roller bearing On the entire width, but concentrated on one side, forming a point contact, so causing one side to peel off. Therefore, it should be ensured that the bearing housing and the shaft have sufficient strength during design, and the fit between the parts is reasonable to ensure the rigidity.
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