Development of Deep Desulphurization Process for X65 HIC Resistant Pipeline Steel

The effect of ladle slag composition, bottom stirring intensity, and refining duration on desulphurization (De-S hereafter) behavior was investigated in ladle furnace (180t) through production data analysis and plant scale experiments. The results show that the ladle slag composition for deep De-S is w(CaO): 50%-55%, w(CaF2): 3%-7%, w(Al2O3): 20%-25%, w (SiO2) <10%, w (MgO) <10%, and w(FeO) <0.5%; De-S ratio doubled from around 10% to around 20%, within the selected period of 8 min with the increase of Ar flowrate of bottom blowing from 400 L/min to 600 L/min; sulfur can be reduced to less than 10 ppm from around 35 ppm within 20 min if the Ar flowrate is kept at 600 L/min; during steelmaking trial of X65 HIC resistant steel, the sulfur content of final product was controlled to be below 10 ppm when sulfur content of the melt at BOF blowing end was kept below 60 ppm, De-S was carried out with the above mentioned slag, and 600 L/min Ar stirring for more than 20 min.