Cylindrical roller bearing outer ring raceway spalling CAUSES
|
| Time：2016.09.10 News Sources：Shandong Xinkaite bearing Co.,Ltd. Views：
|
| 1 Introduction Rolling under certain conditions of use, often because of the impact of internal or external factors, does not reach its calculated life occurred early damage. Analysis of rolling bearing early damage occurs, wherein the bearing outer ring raceway spalling is an important factor. Based on the study on the basis of previous test results, for cylindrical roller bearing outer ring raceway spalling analysis of the causes, and the corresponding improvement measures. Analysis of test results in the past 2 2.1 macro analysis of the occurrence of bearing outer ring raceway spalling visual inspection, most of its distribution area peeled off the side of the raceway, peeling off the area, all the rollers cylindrical surface distribution of many thermal oxidation discoloration dark brown stripe in the raceway spalling at the corresponding side of the rollers, oxidation discoloration is more serious, there are many surface-marking, roller side face wear abrasion, the other end face near the outer diameter by mild oxidation discoloration ring, light brown. 2.2 Analysis of the chemical composition of the chemical composition of the bearing outer ring, with the results as follows: Table 1 chemical composition /% C Mn Si Cr SP 1.02 0.36 0.30 1.55 0.013 0.004 2.3 Determination of hardness hardness (HRC) determination results in Table 2: Table 2 position of the ferrule end surface coat (typing surface) end surface (non-typing surface) outer diameter of the inner diameter (raceway) 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 (level) microstructure (level) oxide sulfide dot deformation sulfide with carbide eliquation network carbide 1.5 2.0 0 1.5 0 1.5 currently, foreign bearing materials most used vacuum deoxidation steel , oxygen content in the provisions of 15ppm or less, while only individual mills in order to meet this requirement, most other mills do not have the condition, causing the roller material organization more than 4, more crack. In the analysis of the quality of materials, non-metallic inclusions and microstructure using YJZ84 standard comparative analysis of the ferrule sulfide impurity level exceeded. To peel off the outer ring is detected, the peeling at the source, from the source 0.5mm ~ 1mm longitudinal grinding metallographic sample observed in peeling away from the surface of 0.36mm-0.49mm range, there is a chain of brittle inclusions, such inclusions there was a fine place shock pattern. On the same metallographic sample, slightly off at the source, from the peel surface about 0.8mm at the chain there are also brittle inclusions. Peeling source along the longitudinal grinding metallographic sample, at the source and its vicinity, also observed a chain brittle inclusions. In the peeling surface 0.3mm pitch at the inclusions have tiny cracks, peeling away from the surface there are about 0.68mm 0.56mm at a chain brittle inclusions. Above shows the raceway in the outer surface there are many chain brittle inclusions, and some have more than specified on the YJZ84 standard quality level. For the outer ring of the microstructure in the release at the source of the release surface tissue into fine crystalline martensite needle fine granular carbide + martensite + residual austenite + zonal distribution of a small amount of points, needle Wyman body. At the edge of the peeling, flaking raceway surface has not yet, but under the surface there are parallel cracks raceway surface tissue into fine crystalline martensite needle fine granular carbide + martensite + residual austenite + a small amount of points, needle troostite. With the internal depth, non-martensite increased, but at 3mm from the surface, non-martensite exceeds a predetermined level qualified. 2.5 Analysis by heat treatment quality ring bearing parts heat treatment quality inspection standard inspection, the outer ring quenching, tempering tissue (Table 4). Table 4 depth from the surface / mm Surface 1.0 2.0 3.0 organizational level / grade 6 <7 <993 Conclusions 1. From the macroscopic organization, the peeling partial raceway side, mainly bearing force direction biased in use, so that roller contact with the raceway uneven bearing raceways produced a limited area overload load bearing outer ring raceway cause early fatigue spalling. Therefore, the rolling bearing during installation, you should avoid the inner and outer inclined, so that the rollers in the raceway uniform contact, avoid local overload, while in the course of the bearing, should try to avoid bearing inclination to work. In addition, the generated power is also due to the intensity of the partial bearing housing and the shaft about because with the strength of the support shaft or housing or part of the difference between the irrational, rigid enough, resulting in the tilt axis of the jacket, so that stress is not distributed in strong cylindrical wet machining systems market prospects experts pointed out, wet machining chip removal and coolant purification system in China has just started, most of the machining businesses of their lack of understanding. Such as to promote the application of the system, will have a significant economic and social benefits, the market has broad prospects. It is understood that wet machining systems have been widely used in foreign industrial countries, and properly solve the metal cutting process in a series of problems, and promote the development of production. In China, now widely used in stand-alone cooling and lubrication, only in a few technologically advanced plant uses a centralized cooling and lubrication systems. According to the national plan, by 2010, Chinas auto output to reach 6 million, the need for large-scale technological transformation engine plant. For this reason, in some high-volume production machining factory and bearings, motorcycles, tractors and other industries to promote the application of wet machining system it is very necessary. It can promote Chinas machinery products more quickly into the international market, foreign exchange revenue for the country while reducing imports of such equipment. Mechanical Engineers Trailer Section 5 ISSUE modern mechanized mold technology renewal Fenghua Wei Cheng Du Zhijun said Tang Xiaohui Zhonggao Yan Liu Feng Dong Zhaolin Renyu Bo Cong Juan loud white Chengzhi Zhang You Xin Li Jun Han Sung Ho pressure vessel structure of large-scale development trend of automatic feed lathe tailstock boring shaft hole short and straight edge to scrape CNC indexable hob C616 lathe CNC lathe with a modified oil pipe thread with AutoCAD drawing parts catalogs group technology Development easy car CAD application locomotive axle grinding line measurement system brake drum boring machine design and manufacturing to improve the structural strength of parts of polytetrafluoroethylene design measures and its application three cases of one kind of rolling pipe filter improved design improved sealing means to solve the fuel tank leakage roller bearing outer race across the entire width, but on the side, forming a point contact, so while causing spalling. Therefore, the design should ensure that the bearing housing and the shaft has sufficient strength, and reasonably fit between the various parts, to ensure its rigidity. 2. the quality of materials analysis found that the outer raceway spalling source outside the chain there are more brittle inclusions and carbide zonal distribution, the presence of a chain of brittle inclusions destroy the continuity of the matrix, it is conducive to crack initiation carbide zonal distribution as favorable to crack initiation. Visible, non-metallic inclusions is inherent causes early chipping of the raceway. Therefore, in the metallurgical quality bearing steel should be strictly controlled. In addition, by oxygen steel spot checks found that some steel oxygen content as high as 35ppm, far beyond the standard. Some steel did not take any measures deoxygenated, causing bearing life severely affected. It should therefore be strictly bearing raw materials, steel selection of quality raw materials. 3. Quality of ferrule heat treatment in order to obtain martensite, and the heating temperature must be increased by rapid quenching oil, and this has brought the heat treatment of stress concentration and other issues, such as oil groove, typing, even surface collision moment, after the heat treatment will lead to stress cracking. Therefore, in order to prevent the accumulation of stress before the heat treatment step is necessary to lay the foundation in sewing, such as car oil groove, to make the tool holder Fengrui chamfer, to reduce typing words, reduced depth. Prevent bump injury in car transport labor movement and so on. Heat treatment process, try to press different "wall thickness" adjusting the heating temperature, the temperature control in the lower range, and fully cooled. With regard to organization heat treatment, according to the chemical composition of steel, shall determine the allowed level. In addition, a large area of the raceway spalling may also be related to the depth of martensite, martensite depth should be more than 3mm, and thus how to reduce the amount of martensite and less than 3mm quenching cracks will not cause future study. |
|
