Practice of Sulfur Content Control During the Smelting of Ultra-low Sulfur X65QS Pipeline Steel

The production process of sulfur content control during the smelting of ultra-low sulfur X65QS pipeline steel in Yong Gang steel used 110 tons of electric furnace,LF refining,VD refining and continuous casting is present in this paper.The sulfur content at each individual process steep had been strictly controlled and average desulfurization rate is achieved at 16.35% for electric furnace.During tapping aluminum addition is 1 kg/t molten steel for deoxidation,at the same time the lime and synthetic slag for refining are added at rate of 6 kg/t and 2 kg/t,respectively.Al wire is used in the LF furnace,composited Si C and Al shot are added for the slag surface diffusion deoxidization.And the resulting high basicitgy white slag are used for deep deoxidization and desulphurization.Desulphurization rate averages at 89.2%for LF furnace.The average sulfur content is 0.000 93% after LF refining.The average resulfurization is 0.000 1% through the end of LF refining to continuous casting steps.And the end sulfur content is 0.000 9%.By controlling the sulfur content in the charge,improving deep desulfurization in the LF refining furnace,and preventing the resulfurization after refining,the sulfur content of X65QS round bloom is far below specified 0.002% level.