In‐situ observation of slag penetration into MgO refractory

Abstract

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.

On different modifications of the capillary model of penetration of inert liquid metals into porous refractories and their connection to the pore size distribution of the refractories

“…From this, one can conclude that the data of Table IV can be extrapolated for any liquid metal, penetrating into the same refractories, provided that the liquid metal is inert and its basic physical properties are known. Physical properties needed for such calculations and [15], using empirical values of Tables I and III (in (c), the theoretical pre-penetration limiting curve cannot be calculated, as experimental data at low h max values are missing from Fig. 5(c), and so ⌬P th,min is not known).…”

“…[14b] and [15], and are compared with the measured data in Figures 10(a) through (c). One can see that our theoretical limiting curves are indeed limiting all data points from the top, and are also reasonably close to the highest data points.…”

“…After the liquid front has passed the first pore with the smallest radius (the "bottle neck" of the refractory), at the given value of h, it will go up practically with no barrier along subcapillaries with larger diameters to the next bottle neck, situated higher by height L. However, at this height, it can be squeezed through the same smallest capillary radius again, if the outside pressure is higher by the gravity term · g · L. Thus, the average slope in coordinates h max Ϫ ⌬P o during the bulk-penetration period will equal L/( · g · L) ϭ 1/( · g), which is the same as for the classical capillary theory. Then, if the maximum penetration height at ⌬P o ϭ ⌬P th,max equals L, the dependence of the maximum height on the outside pressure in the bulk-penetration region can be described by the following equation: [15] In Figure 9(b), the schematic penetration diagram is shown, calculated by Eqs.…”

“…Therefore, in articles published in the field of metallurgy, usually the maximum height of penetration of a liquid metal is studied as a function of the applied pressure. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Thus, the main interest of metallurgists, foundrymen, and ceramists serving these industries is to avoid any penetration. Thereby, the main interest is the thermodynamic aspect of penetration, while kinetic issues are of secondary importance.…”

“…[16][17][18][19][20][21] Particularly, it was experimentally established by us [21] that the penetration diagram of nonwetting liquid metals into alumina refractories can be divided into two stages:…”