Rolling to the tension, compression, bending under complex stress state, cut, alternating, etc., and high stress, high-speed, long-term work. Therefore, in the production process, quality control inspection items bearing steel more control range and narrow, strict production process, complex and requires a certain amount of tooling equipment, testing means and a certain level of villain technology. To ensure the bearings have good performance and a high life expectancy, the quality of bearing steel requirements are as follows:

     (1) The chemical composition: Chemical composition is the most essential factor of bearing steel. Steel physical, chemical, mechanical properties and microstructure are determined by the chemical composition, changing the chemical composition, to change the basic nature of the steel. Thus, the chemical composition of bearing steel must meet the standards specified allowable range.

     (2) Internal quality: quality can be divided into macro and micro quality.

     Macro Quality: Requires bearing steel is not allowed inside the white spots, shrinkage, slag, people kind of metal, crack, over-burning, skin bubbles and other defects. Requirements bearing steel internal segregation, loose control within a certain range. In short, the bearing steel to dense, not allowed to have visible flaws separate substrate steel.

     Microscopic quality: bearing steel internal organizational requirements should be uniform, higher purity.

     Bearing steel strip within the organization refers carbide, carbide mesh, carbide liquation and annealing tissue. Carbide is a major component of bearing steel, is an objective reality, how to make a uniform distribution of carbides, dispersed, small, is an important issue to improve the quality of bearing steel. In recent years, bearing steel major manufacturers use a high temperature diffusion process, controlled rolling new technology and continuous annealing equipment. Even so, the distribution of carbides can not achieve the desired extent. Therefore, the standard provisions allow their scope and level of control.

     Purity bearing steel refers to the degree of contamination of non-metallic inclusions in steel. Non-metallic inclusions are people substances bearing steel matrix, destroy the continuity of the matrix, is caused by bearing early fatigue, one of the main flaking. Therefore, the required amount of non-metallic inclusions in bearing steel as possible. In order to limit the control the presence of non-metallic inclusions in steel, in the standard, they conducted a rigorous level of control. Manufacturer except remelting furnace smelting processing, but also by the external electric smelting furnace plus refining, vacuum oxygen, argon treatment furnace powder processing and other technology, to try to make steel in the oxygen content is reduced to below 20ppm.

     (3) Surface quality: molding method bearing parts, there are currently forging, turning and cold-like. Depending on the method of forming the steel surface with varying degrees of quality requirements. Overall, the bearing steel surface without cracks, folding, crack, scarring and slag. Cold punch with the cold-drawn steel, in addition to not allow the above drawbacks, the surface should be clean, without rust, hemp concave defects. Bearing steel surface may not have serious decarburization phenomenon, according to the different requirements of bearing parts molding process, in the standard for steel surface decarburization depth different varieties have different restrictions.

     (4) Size tolerances: The bearing parts molding technology and production process of steel, in the standard of bearing steel of various varieties and specifications of dimensional tolerances have been specified. Forged steel dimensional tolerances generally according to GB908-72 standard, hot-rolled steel dimensional tolerances according to GB702-86, according to GB905-82 standard cold-drawn steel, cold-drawn steel wire according to YB245-64 standards.