abstract
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The rate of corrosion of silica and alumino-silicate refractories in Armco iron and iron-carbon melts was measured. An interpretation of the rate data required an experimental investigation of the kinetics of the reactions between iron oxide and silica, and carbon and silica.
A standard "immersion" technique was used under both static and dynamic conditions. The corrosion of the refractories in Armco iron melts was initially controlled by a chemical reaction process but changed rapidly to a steady-state, diffusion-controlled process. A liquid silicate product layer built up at the interface during the induction period. The steady-state rate of corrosion was independent of the oxygen content of the melt and was also found to be a linear function of the peripheral velocity of the refractory specimen. The rate of corrosion for the various refractories was measured and found to be controlled by diffusion of iron and oxygen in the silicate layer.
The rate of corrosion of these refractories in carbon-saturated iron melts was also studied. The rate was found to be independent of the silicon concentration and the carbon concentration in the melt (in the range 2.3%C to saturation). The rate was independent of the rate of rotation of the refractory specimen. The results were interpreted in terms of chemical reaction control at the refractory/metal interface, with the dissociation of silica proposed as the controlling reaction. The rate was found to be strongly temperature dependent indicating reaction control.
This experimental investigation has provided new insights into the mechanism of corrosion of silica and alumino-silicate refractories in iron melts.