When the original carbides are small, because carbide easily into the austenite, so after quenching hardness peaks shift to lower temperature and in short of austenitizing time, in order to make the material factors affecting SKF bearing life at its best, first of all need the original organization control before quenching steel, technical measures can be taken a: high temperature (1050 ℃) austenitic fast cooling to 630 ℃isothermal normalizing gain quasi-eutectoid fine pearlite, or cool to 420 ℃isothermal treatment, obtain bainite forging waste heat can be used to obtain rapid annealing, fine granular pearlite in steel, in order to ensure the fine and homogeneous distribution of the carbide the original microstructure in the quenching austenitization, in addition to dissolve in austenite and carbide, undissolved carbide will gather fine-grained whole camshaft bearing should be complex in tension, compression, bending, shear, alternating stress and high stress, high speed, long time working. Therefore, in the process of production, bearing steel quality control inspection items, control range is narrow, strict production process, complex, require certain equipment, inspection means and a certain level of villain technology. In order to ensure the SKF bearing has good performance and high life, on the quality of bearing steel requirements are as follows:
( 1 ) chemical composition: chemical composition is the most essential factor of bearing steel. The physical, chemical, steel, mechanical properties and microstructure are determined by chemical composition, changing the chemical composition, changes the basic properties of the steel. Therefore, chemical composition of bearing steel must conform to the standards prescribed limits.
( 2 ) the internal quality: can be divided into the macroscopic and microscopic quality quality.
The macro quality: requirements of bearing steel is not allowed to have white spots, shrinkage, slag, and metal, crack, overheating, such as subcutaneous blowhole defect. Requirements of internal segregation, the eccentric bearing steel osteoporosis is controlled in a certain range. In a word, bearing steel interior to be tight, does not allow the substrate to visible defects separate steel.