Resulfurization behavior of pipeline steel in a converter steelmaking process

The strategies for controlling resulfurization in a converter steelmaking process were clarified to produce pipeline steel with the KR–LD–RH–CC route, and the influence factors of resulfurization were investigated based on the industrial data and theoretical analysis. The results show that KR slag and lime account for the largest proportion of the sulfur-bearing materials of the sulfur in the converter. The influence of sulfur fluctuation in lime on the resulfurization was also significant. The removal ability of KR slag was greater by using a crawler loader than by using a slag-dredger. The steel resulfurization can be more effectively restrained by a conventional converter process than by a duplex converter process. Moreover, the rate-limiting step of the resulfurization in the converter is considered to be the mass transfer of sulfur from the interface toward the bulk of the slag phase, and slag with doubly saturated MgO and 2CaO•SiO2 was proposed to restrain the rate of resulfurization without changing the dephosphorization rate. The industrial experimental results show that the sulfur content of the steel before tapping into the ladle can be controlled at 0.002% to 0.003% when employing the above controlling strategies.