The metallurgical quality of bearing steel basic request

The use of the rolling bearing life and reliable level and the metallurgical quality of bearing steel have a close relationship. Due to the nature of bearing steel has, on the request of the metallurgy quality than ordinary steel used in industry are much more severe.     1 the chemical composition of strict request & emsp;   Ordinary rolling bearing steel high carbon chromium bearing steel, the carbon content 1%, to 1. About 5% of chromium and contains a small amount of manganese and silicon hypereutectoid steel. As long as the chemicals in the strict control of bearing steel, after heat treatment process wait to satisfy the bearing performance of talent structure and hardness.     2 high dimensional accuracy & emsp;   On request of rolling bearing steel steel dimension precision is higher, this is due to the large local are through processing and shaping pressure bearing parts. Frugal data and progress to the labor consumption rate, most local bearing ring type are formed after forging, 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, can't accurate calculation of blanking size and weight, can't ensure the quality of bearing parts production volume, easy to form a set & emsp;   Prepare and mould damage.     3 special severe degree of pure request & emsp;   Steel in the pure degree is to point to a few contain nonmetallic inclusion in steel, pure degree is higher, the lower the content of non-metallic inclusions in steel. Oxide, silicate, dot deformation of bearing steel inclusion harmful inclusions is incurred such as bearing early fatigue spalling, significantly reduce the bearing life of the main reasons. And brittle inclusion in the grinding process is peeling off easily from the metal substrate, seriously affect the appearance quality of bearing parts after finishing. In order to advance the use of bearing life and strong sex, must reduce the amount of non-metallic inclusions in bearing steel.     4 serious macrostructure and microstructure, At high magnification) Organization request & emsp;   Bearing steel macrostructure means normal loose, loose center, and segregation, microstructure, At high magnification) Organizations including annealing of bearing steel, carbide mesh, strip and liquid chromatography. The merits of the low and high power organization performance and use life of the rolling bearing has a great influence. So, in the bearing steel material specification has strict request for low and high power organization.     5 special stern appearance defects and internal defects request & emsp;   For bearing steel, including appearance appearance defects cracks, slag inclusion, burr, folding, scarring, scale, etc. , internal defects including shrinkage cavity, bubbles, white spots, burnt, severe osteoporosis and segregation, micro pore, etc. These defects of bearing processing, the bearing performance and using life has a great influence, in bearing steel material specification written rules do not allow these defects.     6 particularly severe carbide not mean sex request & emsp;   In the bearing steel, if the present carbides distribute uneven, easy to form the organization in the process of heat treatment processing and uneven hardness. In the area of carbides distribute less, constitute a martensite acicular structure, hardness is low. In the rolling bearing parts heat treatment technical conditions, the structure, hardness and hardness after the heat treatment of the average sex has the strict request, moreover, carbide average sex is not easy to make the bearing parts during quenching cracks, carbide unequal sex also incur lower bearing life.     The decarburization layer 7 special stern appearance request & emsp;   In bearing steel material specification for the appearance of steel decarburized layer has strict rules, if the decarburization layer appearance is beyond the scope of standard rules, before the heat treatment process in not to clear it all away, so easily in the process of heat treatment quenching, quenching cracks form the scrap parts.