Optimization of Refining Slag Composition and the Deoxidation Practice of Liquid Steel in BOF-CAS-CC Process

摘要

The cleanliness level in the slabs of micro-alloy structure steel produced in the BOF-CAS-CC process was studied by optimizing the compositions of molten steel and refining slag in trial heats. When the slag composition was controlled in the range of CaO = 45-53 wt%, Al2O3 = 28-32 wt%, SiO2 = 6-11 wt% and MgO = 5-10 wt% in CAS, the steel composition should be in the range of [Al-s] = 0.025-0.035 wt% and a([O]) = 0.8-1.5 ppm. After CAS treatment without feeding calcium, the results showed that the removal ratio of total oxygen content increased to 61% and the nitrogen content decreased from 34 to 13 ppm in the improved process. The residual micro-inclusions in slabs mainly consisted of SiO2-Al2O3-TiO2 and sulfides, and the particle size was predominately below 5 mu m.