MICROSCOPIC STUDY ON SLAGGED HIGH-ALUMINA ARC FURNACE ROOF BRICKS

An aspect is summarized of microscopic studies on certain slagged high-alumina bricks dismantled after arc furnace roof service with various steel smelt-ing operations in the past years since 1957. The bricks were attacked mainly byMgO, CaO and iron oxides. The MgO had its sources by evaporation and infiltra-tion from either magnesite fettling material or basic furnace wall under highertemperatures. It was identified by X-ray powder pattern and by microscopic ob-servation that the periclase grains or/and needles occur in the slagged zone ofbricks. The iron oxides, if presence, accumulated themself mostly on the surfacelayer of slagged zone, formed an assemblage of reaction products and convertedinto two systems of ferro-spinels as (MF')A and (F'M)F. However, only MAspinel was formed with less iron oxides content. Other equilibrium phases contain-ing CaO may be monticellite and anorthite. The reaction products observed seemto be calcium- hexaluminate and gehlenite in the inner layer of slagged zone,and a certain amount of glass is also present.