Behavior of Mold Slag Used for 20Mn23Al Nonmagnetic Steel During Casting

Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition. A new mold slag with low melting point and low basicity was proposed. The initial slag (the base mold slag) and two corresponding mold slags sampled after 8 min and 15 min were investigated, and the changes of mold slag composition and properties of molten slag were discussed. The results showed that the slag quickly changed in chemical composition to a slag that contained a small quantity of silica and a larger quantity of alumina, and the basicity increased obviously; the heat flux density through the slag film decreased slightly compared with the slag film at 0 min, 8 min and 15 min; the mold slag used for nonmagnetic steel was precipitated as CaF2 crystals. The casting experi, ment shows that the slab has good surface quality without longitudinal face cracks and slag inclusions; the Al2O3 content in the molten slag pool increased with time at the beginning stage, and it can approach equilibrium state after about 600 s.