The behavior of slag penetration into MgO refractory was investigated by combining in‐situ X‐ray observation with microstructural analysis of the samples after penetration experiments. The following results are obtained. The slag penetrates rapidly into the refractory, reacting with MgO particles in the refractory. The slag penetrates unevenly into the refractory with uneven pore size in a route like a tree, firstly along the main route (the surface of large MgO particles), and then extending to the branch route, while evenly into the refractory with even pore size. The rate of slag penetration increases with increasing pore radius and apparent porosity of the refractory, T · Fe concentration in the slag and temperature, and with decreasing the slag basicity (C/S ratio). In the case of the Al2O3‐bearing slag, the rate of slag penetration is less than that of Al2O3‐free slag in the initial stage. The penetration also stops much earlier than that of the Al2O3‐free slag, and then the penetration height remains almost constant. In the initial stage of penetration, the penetration height is proportional to the square root of penetration time. Slag penetration is deduced as stopping due to the following: (1) the melting point and viscosity of the penetrated slag increase, and the surface tension of the penetrated slag decreases with decreasing the FetO concentration in the penetrated slag consumed by the reaction between FetO and MgO particles; (2) in the 10mass% Al2O3‐bearing slag, the pore size in the refractory is reduced by the spinel formed on the pore surface by the reaction between Al2O3 in the penetrated slag and MgO particles in the refractory.

-1 Sensui-cho, Tobata-ku, Kitakyushyu-shi 2-1 0-1 1 Ano, Yahatanishi-ku. Kitakyushu-shi, 806-0049Japan. 804-8550The behavior of MgO-C refractory-slag-metal

The local corrosion of MgO-C crucible by molten slag (Ca0-Si02-Al 2 03-(Fe,0)) and metal is greatly influenced by the bubbles generated at the crucible-slagmetal three-phase boundary and at the crucible-metal interface. Bubbles generated at the crucible-slag-metal three-phase boundary suppress the local corrosion, while bubbles generated at the crucible-metal interface enhance the local corrosion. Mechanism of the bubble generation was studied by in-situ X-ray observation and also by theoretical analysis. It is revealed that bubbles form mainly according to the reaction between (FeO) in the slag film between crucible and metal and C (s) in the crucible: (FeO)+C( S) =Fe ( i ) +CO (g) . (FeO) in the slag film comes from the reaction: 2Fe+(Si0 2 )=2(Fe0)+Sj for the FeO-free slag-electrolytic iron system.