Bearing failure reason analysis

2020 - bearing failure cause analysis 03 - 02 Han Yulong ( Mechanical and electrical design and research institute of Shanxi Province) To failure of the mining damage to the bearings of planetary gear reducer as an example, analyzed the damage of bearing parts chemical composition, hardness, microstructure, to determine the causes of bearing failure. 1, appearance inspection roller surface with indentation, pitting and extrusion deformation are traces of local spalling damage, inner ring guard circumferential failure. Marks extrusion on the surface of the outer ring fracture broken, visible circular raceway surface traces to the processing of grain. 2, chemical composition and hardness test testing fruit showed that the bearing outer ring, inner ring material chemical composition, respectively, in accordance with high carbon chromium bearing steel GCr15SiMn composition, roller material chemical composition accords with GCr15 composition; Bearing inner ring and outer ring and roller hardness values conform to the hardness of high carbon chromium bearing steel rolling bearing parts requirements. 3, metallographic examination, the failure of bearing in the test room for low power hot acid leaching test, the low power hot acid leaching test results show that the dendrite segregation exist in the inner ring and outer ring steel, steel roller exist in the central zonal segregation, affect the mechanical properties of bearing steel, heat treatment and machining process may also be affected. 4, analysis of fracture surface of the outer ring raceway marks extrusion, circular raceway surface visible to the processing of grain traces, outer ring raceway surface is rough, the trough of the raceway surface is larger, they are like Angle gaps and cracks, sensitive to stress concentration, cause and cylindrical roller surface contact stress increase, affect the bearing performance and service life, is a major cause of premature failure of the bearing. Used in bearing inner ring and outer ring and used unbroken roller hardness value consistent with high carbon chromium bearing steel rolling bearing parts hardness requirements. Bearing damaged pieces of inner ring and outer ring, roller material chemical composition can meet the demands of high carbon chromium bearing steel components respectively. Low power hot acid leaching test results show that the dendrite segregation exist in the inner ring and outer ring steel, steel roller exist in the central zonal segregation, segregation, and affect the mechanical properties of bearing steel, heat treatment and machining process may also be affected. Non-metallic inclusion test analysis showed that the roller C inclusion in steel level does not accord with standard requirements. Carbide nonuniformity analysis shows that the roller banded carbide to 2. Level 5, carbide network is greater than 3. Level 0, and GB/T18254 - And JB/T1255-2002 The bearing steel parts in 2001 carbide network is not greater than 2. The requirements of grade 5. Segregation, non-metallic inclusions in bearing steel and carbide morphology and distribution is influence the main factors of mechanical performance and service life of bearing parts; Cylindrical roller bearing is line contact way, contact stress is large, under every point on the cylindrical surface of roller can all be working point, the segregation, non-metallic inclusions and carbide morphology and distribution uniformity have more strict requirements; Damaged roller center banded segregation internal defects, class C inclusions in steel level does not accord with standard requirement, damaged roller carbide network is greater than 3. Level 0 do not tally with the standard requirements; Non-metallic inclusion, reticulate carbide segregation and overweight, is a major cause of bearing roller failure. Five, conclusion bearing inner and outer ring and roller material chemical composition are conform to the composition of high carbon chromium bearing steel. Bearing inner ring and outer ring, roller hardness conforms to high carbon chromium bearing steel rolling bearing parts hardness requirements. The circumference of the outer ring raceway surface is visible to the processing of grain, rough surface, causes and cylindrical roller surface contact stress increase, is a major cause of premature failure of the bearing. Bearing roller segregation, non-metallic inclusions in steel and carbide network, is the main factor of bearing roller failure. Source: 'mechanical engineering and automation' 01, 2019