Criteria for choosing refractories in aluminum holding and melting furnaces

Refractories in aluminum holding and melting furnaces are corroded, in service, by the action of molten metal, under the influence of the surrounding atmosphere, as well as the thermal gradient lying across the metal line, where fluxing agents are often used. Such corrosion may involve internal and/or external corundum growth, depending on the position of the refractory material with respect to the metal line. Testing procedures and criteria are presented in this paper to permit the selection of refractories offering maximum resistance to corundum growth at and below the metal line in holding and melting furnaces. The effects of the materials' composition and porosity on their corrosion resistance, in such applications, are also discussed.