Effect of Slag Composition on Inclusion Composition in Molten Steel

摘要

It is well known that MgO- Al_2O_3 spinel-type inclusions in steel products often cause cracking and surface flaws because of their high melting temperature and low deformability. In addition, they raise a serious problem for operation by causing nozzle clogging. Thus, it is necessary to control the composition of inclusions in steel in order to suppress the formation of spinel-type inclusions.Many researchers have studied the formation mechanism of spinel-type inclusions. Spinel-type inclusions are thought to be formed by the reaction between alumina-type inclusions and Mg, which is formed in the molten steel through the reduction of MgO in the slag or refractory by Al. Some researchers have pointed out that changes in the slag composition affected the formation of spinel-type inclusions When the slag basicity CaO/SiO_2 and CaO/Al_2O_3 is higher, reduction of MgO in the slag is suppressed. This means that decreasing slag basicity is effective for suppressing the formation of spinel-type inclusions. Although the qualitative control method for spinel-type inclusions is understood, few studies have mentioned the quantitative control method.