Study Of The Mechanics Of Ladle Slag Buildup And The Slag Melting Agent

The slag buildup of ladle lining has become a very important factor influencing the normal continuous casting process in recent years. Aiming at the buildup of ladle lining of a steel works, the residual ladle lining, the physicochemical property of fused slag, the ladle lining refractory after slag corrosion test were investigated in this paper, then extracted the mechanics of slag buildup of ladle lining and developed a slag melting agent. The results are obtained as follows:(1) The original material of slag line is alumina-magnesia brick, and the original material of ladle wall is alumina-magnesia-chromium brick. The CA₂ and C₂S formed at the slag buildup layer, the zonal distribution MA spinel at the action layer, the prismatical phase CA₆ in alternate direction and continuous grainy MA at penetration layer in the slag line sample. The well grown FA phase formed at the slag buildup layer, the phase CA₆ in the spindly shape at the reaction layer, a plentiful MA spinel at the permeation layers in the ladle lining sample. The corundum grain and MA formed at the hyle layer.(2) The Al₂O₃ content raised while CaO content declined generally with the going of refining process. The melting point of fused slag ranged from 1242℃to 1428℃, however the relation of melting points and viscosity with chemical composition and alkalinity were not clear. The XRD results show that some slag were at amorphous state, some were at the calcium ferrite, calcium silicate, spinel, melilite and some complex solid solution form.(3) The slag corrosion test showed that the major phase of slag line brick was MA spinel after corroded by the grain-oriented silicon steel slag, and the link of spinel grain was incompact; while the major phase of brick were plentiful prismatical CA₂ and CA₆ phase after corroded by the Aluminum killed steel slag, and plentiful MA spinel formed at penetration layer near the hyle layer.(4) Because of the blocking layer has been destroyed by the low melting point phase CA existing as a discontinuous layer, the corrosion and penetration increased with the increased CaF₂ content in the slag melting agent.(5) The components of ladle brick and fused slag penetrated into each other, then the CA₂, CA₆, MA phase formed at the acting surface of brick. The presence of phase CA₂, CA₆, FA, MA of high melting point forms a blocking layer between slag and brick, some formed at the hole of brick, the pore space of grain, intercrystalline as a clogging phase which could inhibited the further penetration of slag into brick. The new action product layer formed at the blocking layer, then the ladle lining become thicker, the slag buildup become more severe when the Aluminum steel smelted. However, the incompact blocking layer would destroyed because of the high temperature, vacuum and mechanical washing under RH refining process, then the ladle lining become thinner when the grain-oriented silicon steel smelted.