Mullite-corundum articles based on a phosphate binder

Abstract

By comparison with the sintered corundum filler, the electrosmelted product is a lower quality corundum article in relation to density, strength, and thermal shock resistance [1-3] but better in the resistance of the refractory to wear. To improve the thermal-shock resistance, silica-containing additives are added to the composition [3-7] and these form mullite encrustations. The best properties in corundum articles on a corundum-mullite binder are provided by the addition of a disthene--sillimanite concentrate and the worst when refractory clay is used.To improve the pressability, increase the density, and improve the strength of the articles, an addition of 4-6% of orthophosphoric acid is made [8].

Corundum-chromite refractories with improved thermal-shock resistance

“…In accordance with the results in [5], in order to increase the thermal-shock resistance of the specimens the compositions 9 and 12 were repeated (composition A and B), by altering the preparation procedure; the grains of the filler were moistened partly with aluminophosphate bond, and then chromium oxide was rolled on to them (A), or aluminochrome scrap (B). After hardening the shells we again wetted the grains with the remaining part of the bond; then we introduced finely milled alumina, i.e., we formed a chrome-containing shell around the grains.…”

“…The incorporation of chromium oxide by rolling on the bond-moistened grains of corundum (A) gave the expected [5] increase in thermal-shock resistance, but in industrial conditions it is difficult to mold laminated structure. Using nontraditional sources of raw material not only extends the raw material base for refractories production but also uses up scrap from certain chemical production.…”