Study on the differential modification of TiN and sulfide inclusions in 20CrMnTi gear steel by rare earth La and Ce elements

Abstract

The occurrence form and size distribution of TiN and sulfide inclusions in 20CrMnTi gear steel directly affect the mechanical and service properties of the steel. Mastering efficient modification methods for TiN and sulfide inclusions in steel is of great significance. In this article, the differential behaviors of rare earth La and Ce on TiN and sulfide inclusions modification of 20CrMnTi gear steel are studied. The results show that the addition of rare earths La and Ce can modify the large TiN and sulfide inclusions into smaller composite inclusions. When rare earth La element (Abbreviated as RE La) is added to steel, the TiN and sulfide inclusions in steel are modified to small size LaAlO₃-TiN, LaAlO₃-MnS-TiN composite inclusions. When rare earth Ce element (abbreviated as RE Ce) is added to steel, the TiN and sulfide inclusions in steel are modified to small size CeAlO₃-TiN and CeAlO₃-MnS-TiN composite inclusions. The effect of RE Ce on TiN modification is better than that of RE La. When RE Ce is added, the average size of TiN inclusion in steel is 2.77 μm, and when La is added, the average size of TiN inclusion in steel is 3.24 μm. The modification effect of RE La on sulfide inclusion in steel is better than that of RE Ce. When La is added, the average size of sulfide inclusions in steel is 1.72 μm. When Ce is added alone, the average size of sulfide inclusions in steel is 2.08 μm.