The wide variety of refractory materials used for the lining of melting furnaces is explained by the desire to eliminate the interaction between the molten metal and the lining material. Such interaction, apart from mechanical and thermal destruction, can manifest itself in several types: metallization, Exchange reactions between metal and refractory material, between metal oxides and lining, dissolution of the crucible material by metal or its oxides.
Metallization is the impregnation of refractory with metal under the influence of metallostatic pressure and capillary phenomenon. Very often, the metallization process is combined with the chemical interaction of metal with refractory oxides. Metallization of the lining is often found in the production of copper and lead -based alloys. During prolonged operation of the furnace, the metal penetrates to a depth of 1.5—2 m. The seams of the masonry are almost completely filled with metal.
Exchange reactions between the metal and the lining are possible when the chemical stability of the resulting oxide is higher than the strength of the oxide that is part of the refractory. The possibility of exchange reactions is approximately estimated by the standard heat of formation, the change in free energy and the elasticity of dissociation. Pure copper can be melted in furnaces with any lining. Refractory materials containing silicon dioxide are unsuitable for magnesium alloys.
