Research on TiN inclusion modification in 20CrMnTi gear steel by rare earth Ce during Si-Ca-Ba-Ce composite deoxidation

Abstract

The size and distribution of TiN inclusions in 20CrMnTi gear steel directly affect its service performance. A reasonable method for controlling the size of TiN inclusions is a prerequisite for obtaining high-quality 20CrMnTi gear steel. This study focuses on the modification behaviour of TiN inclusions in 20CrMnTi gear steel under the conditions of Si-Ca-Ba single deoxidation and Si-Ca-Ba-Ce composite deoxidation, and their effects on the fatigue performances of the steels. The results show that after Si-Ca-Ba-Ce composite deoxidation, in addition to TiN inclusions, TiN containing composite inclusions such as Al₂O₃-TiN and CaAl₁₂O₁₉-TiN are also generated in the steel. When the ratio of Si-Ca-Ba to Ce in the Si-Ca-Ba-Ce composite deoxidiser is 5:1, the effective modification rate of TiN reaches 48.6%, which is better than 44.8% at 7:1 and 45% at 2.4:1, and the average size of the inclusions in the steel is 2.5 μm, which is better than 2.8 at and 3 μm at 2.4:1. At this point, the effect of the TiN inclusion modification in the steel is good, and the fatigue performance of the 20CrMnTi gear steel has been improved.