The metallurgical quality of bearing steel basic requirements - bearing knowledge

by:Waxing     2020-05-31
The service life and reliability of the rolling bearing to a great extent and the metallurgical quality of bearing steel have a close relationship. Because of bearing steel with the properties, of the metallurgical quality requirement is more strict than the general industrial steel.     1 the chemical composition of strict requirements & emsp;   General rolling bearing steel high carbon chromium bearing steel, the carbon content 1% the left and right sides, add 1. About 5% of chromium and contains a small amount of manganese and silicon hypereutectoid steel. Only strict control of the bearing steel chemical composition, can through the heat treatment process wait to satisfy the bearing performance of the organization and hardness.     2 high dimensional accuracy & emsp;   Requirements for rolling bearing steel steel dimension precision is higher, this is because most are through processing and shaping pressure bearing parts. In order to save material and improve labor productivity, the vast majority of bearing ring have been forging forming, steel ball cold heading or hot forging forming, small size of the roller is through the cold heading forming, if the size of the steel precision is not high, will not be able to accurately calculate the size and weight, can't ensure the quality of bearing parts, easy to cause a & emsp;   Prepare and mould damage.     3 special strict purity requirements & emsp;   Purity of steel is to point to contain nonmetallic inclusion in steel, the higher the purity, the lower the content of non-metallic inclusions in steel. Bearing steel of oxide and silicate inclusions, dot deformation harmful inclusions are bearing early fatigue spalling, the main reason for the lower bearing life significantly. And brittle inclusion in the grinding process is peeling off easily from the metal substrate, seriously affect the quality of bearing parts after finishing surface. In order to improve the service life and reliability of the bearing, it is necessary to reduce the amount of non-metallic inclusions in bearing steel.     Strictly the macrostructure and microstructure of 4 ( At high magnification) Organization requirements & emsp;   Bearing steel macrostructure is refers to the general loose, loose and center segregation, microstructure, At high magnification) Organizations including annealing of bearing steel, carbide mesh, strip and liquid chromatography. Low, high quality of performance and service life of rolling bearing has a great influence. So, in the bearing steel material in the standard of low and high power organization has strict requirements.     5 special strict surface defects and internal defects requirements & emsp;   For bearing steel, including surface crack, surface defect on the surface of slag, burr, folding, scarring, scale, etc. , internal defects including shrinkage cavity, bubbles, white spots, burnt, severe osteoporosis and segregation, micro pore, etc. These defects for the processing, the bearing performance and service life of bearing has a great influence, enshrined in the bearing steel material standard is not allowed. These defects.     6 special carbide not uniformity requirements & emsp;   In bearing steel, if appear uneven distribution of carbides, in the process of heat treatment can cause non-uniform structure and hardness. Based on the distribution of the carbide less area, formed martensite acicular structure, hardness is low. Because in the condition of rolling bearing parts heat treatment technology of heat treatment on structure, hardness and hardness uniformity has strict requirements, and the carbide inhomogeneity is easy to make the bearing parts during quenching crack, carbide inhomogeneity is resulting in a loss of bearing life.     7 special strict surface decarburization layer requirements & emsp;   In the bearing steel material standard has strict rules on the surface of the steel decarburized layer, if the surface decarburization layer beyond the prescribed scope of the standard, before the heat treatment process, no will clear away all the, so easily in the process of heat treatment quenching, quenching cracks cause scrap parts.
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