Abstract: Based on the thermodynamic calculation of complex deoxidization with Al-Si-Mn, a two-step deoxidization process was proposed for Q235 steel. The first deoxidization step was carried out during BOF tapping, with suitable amounts of silicon, manganese and small amounts of aluminum; and the final deoxidization step was carried out during LF refining with aluminum wire feeding. The equilibrium state of the liquid steelslag system was calculated by the thermodynamic software Thermo-Calc. The results show that the dissolved oxygen mass fraction of the molten steel is 1×10-6 and the sulfur mass fraction of the molten steel is 1.5×10-6at LF end. The experiment results show that when the total aluminum mass fraction is 0.004 %～0.015 %, the total oxygen mass fraction is (20－35)×10-6 in steel and the sulfur mass fraction is less 0.012 % in steel at the end of LF refining, and the cost of deoxidized alloys can save 4.2 yuan/t.

Key words: Si-Al killed steel, BOF tapping, two-step deoxidization process, LF refining