Silicon nitride jig for hot rolling

Abstract

A ceramic jig for hot rolling is a sintered body consisting essentially of Si.sub.3 N.sub.4, a sintering aid and trace amounts of impurities. In the ceramic jig, crystallization is made among the Si.sub.3 N.sub.4 grains, and a crystalline phase among the grains comprises 80% or more of a J phase, 10% or less of an H phase and 5% or less of a K phase. A reaction of a jig component with iron and water can be inhibited, and the wear of the jig at the time of rolling can be reduced. The seizure of the jig on a steel material does not occur, so that scratches on products can be remarkably reduced.

Dependencies are inferred from the claim text.