Determination of process parameters for refining of ultra-low sulfur steels in ladle furnace

A thermodynamic calculation method was used to determine the process parameters of ladle furnace for the refining of ultra-low sulfur steels. The ultra-low sulfur content in liquid steel can be reached by using high basicity slag, deeply deoxidizing both slag and liquid steel, reducing initial sulfur contents in slag and steel, and properly controlling slag amount in the furnace. The production practice by a 150 t ladle furnace showed that the sulfur content in steel is 0.0044% after LF refining and 0.0027% after VD treatment, under the conditions determined by the processing parameters proposed by this study. Moreover, the extremely low sulfur steels with less than 0.002% of sulphur content can be produced in a ladle furnace by means of controlling the initial sulfur content to less than 0.058%, or increasing the sulfur partial ratio between slag and metal to more than 250,or applying double slag operation.