Modification Effect and Mechanism of La-Ce on Inclusions in GCr15 Bearing Steel

Abstract

In order to investigate the effect of Rare Earth La-Ce on the modification of inclusions in GCr15 bearing steel， a high-temperature tube furnace with a nominal capacity of 1 kg was used to smelt 6 heats of GCr15 bearing steel ingots with different La-Ce contents. Characterization methods such as optical microscopy and scanning electron microscopy were used， and the transformation law of inclusions in GCr15 steel at different La-Ce contents was studied using FactSage thermodynamic software. The results show that the typical inclusions in GCr15 bearing steel without adding La-Ce are Al2O3 and MnS， and the addition of La-Ce will modify it to more complex Rare Earth inclusions. With the increase of La-Ce content， the transformation law of inclusions in steel at 1 600 ℃ is Al2O3→REAlO3→ RE2O3→ RE2O2S → RE2O2S + RExSy（RE is La、Ce）. With the increase of La-Ce content， the density of inclusions and the average aspect ratio in the steel both decrease first and then increase. When the La-Ce content is 96 ×10-6， Al2O3 and MnS were both transformed into spherical RE2O2S·RExSycomposite rare earth inclusions. The number of inclusions in the steel was at a low level and the overall morphology of the inclusions was well controlled.

Keywords

• gcr15 bearing steel； rare earth； inclusion modification； thermodynamic calculations