Effect of Mn and Si on the Microstructure and Mechanical Properties of Bearing Steel

Two bearing steels, with higher Mn and Si content than GCr15, were refined in 50kg vacuum induction furnace followed by multi-pass rolling to 12mm thick flat on two-high mill. Mechanical properties and microstructures were measured and observed. The results show that higher content of Mn and Si decreases the martensite starting temperature (Ms), which is beneficial to the forming of martensite. The microstructure changes from martensite plus troostite to martensite, leading to higher hardness of steel and improvement of wear resistance. However, the band microstructure is easily formed by increase of Mn and Si, which is harmful to transverse property.