Abstract:

Aiming at the problems such as high total oxygen control and poor control of inclusion in the production of 20CrMnTi gear steel, the effects of bacisity of refining slag, ratio of w(CaO)/w(Al₂O₃), and MI index on the adsorptioncapacity of Al₂O₃ inclusions were mainly discussed through the calculation result of FactSage thermodynamics software in the paper. The results show that the main composition of refining slag suitable for the production of gear steel (20CrMnTi) in the steel plant is as below: w(CaO)=50 %-55 %，w(Al2O3)=22 %-26 %，w(SiO₂)=10 %-12 %，w(MgO)=5 %-7 %. And applying this refining slag in industrial tests, the total oxygen mass fraction decreased from 17×10^-6 to 14×10^-6. Besides, the average size of inclusions in billets also significantly decreased from 2.0 μm to 1.4 μm, and most of the observed inclusions change within the 1 500 ℃ liquidus, inclusion modification effect is good.

Key words: gear steel, LF refining slag, FactSage thermodynamics software, cleanliness