Control of titanium nitride in bearing steel

The formation thermodynamics of the existed TiN inclusion and the control theory of titanium and nitrogen in bearing steel were studied. Then based on the theoretic calculation results, the industrial trials of GCr15 bearing steel were carried out in a steel plant. The results showed that the higher the titanium or nitrogen content in steel is, the higher the precipitation temperature of TiN, and the bigger the size of precipitates;the use of low-Ti alloy materials can effectively reduce the Ti content;using low-Ti molten iron and reducing the TiO₂ content to less than 1.0% in furnace slag can control the Ti content effectively. The use of low-titanium synthetic slag can make Ti content of the steel drop from the original 37×10^-6 to 30×10^-6. Optimized and improved refining processes protective casting process can reduce the N content of 33×10^-6. With the degree of solidification segregation decreases, the precipitation of TiN inclusion is reduced.