Study On The Influence Of Rare Earth Elements On Inclusion In High Purity Bearing Steel

- Mar 15, 2018-

As one of the marks of metallurgical quality, non-metallic inclusions in bearing steel have important influence on the performance of bearing steel, such as type, distribution, size and shape.Al2O3 and MnS are the main non-metallic inclusions in steel.Irregular hard brittle Al2O3 inclusions thermal expansion coefficient is less than the bearing steel substrate, in the hot working process is easy to scratch matrix, and caused by stress concentration after heat treatment, serious deterioration of bearing steel contact fatigue performance, reduce its service life.

The scholars of the institute of metals of the Chinese academy of sciences adopted the method of high purity RE in the high purity bearing steel, and studied the influence of different RE content on the inclusion of high purity bearing steel.By means of metallographic microscope, SEM, EDS and image-proplus software, the inclusions in steel were characterized and analyzed.Results show that the proper amount of the addition of RE can deteriorate inclusions in steel, makes the inclusion distribution more uniform and the size is more small, irregular shape of Al2O3 inclusions and cords of MnS inclusions and metamorphism is ball or elliptic spherical rare earth inclusions, thus improving the quality of bearing steel with high degree of cleanliness.With the increase of RE addition, the inclusion size gradually increased, the appearance was more irregular, and the metallurgical quality of the high purity bearing steel decreased.In addition, the increase of RE addition also makes the mechanism of inclusion size increase from the evolution of precipitate to polymerization.Considering the modification of inclusions and the performance optimization of bearing steel, the best RE quality score of high purity bearing steel should be controlled at about 0.02%.