Alumina-based sintered material

Abstract

A homogeneous alumina-based sintered material having excellent grindability, low porosity and high flexural strength, and which is free of color unevenness and fluctuations in density. Predetermined amounts of Al.sub.2 O.sub.3 powder, MgO powder, CaCO.sub.3 powder and SiO.sub.2 powder are measured out, and then mixed with stirring in a ball mill. The mixture is granulated using a spray dryer, and then hydrostatically pressed to obtain a molded product having a predetermined shape. Subsequently, the molded product is stored and sintered at a temperature of 1,550.degree. C. to 1,650.degree. C., particularly 1,600.degree. C. to 1,650.degree. C. under atmospheric pressure for 2 hours. As a result, an alumina-based sintered material having a 50 percent cumulative grain size distribution in diameter of from 4 to 15 .mu.m, a 90 percent grain diameter of two to three times the 50 percent grain diameter, and a porosity of not more than 5% can be obtained. The alumina-based sintered material thus obtained exhibits a maximum load current during grinding of not more than 1.0 A/mm, particularly not more than 0.5 A/mm, and a four-point flexural strength of not less than 300 MPa, thus providing excellent grindability as well as high strength.