Method for producing a high strength feldspathic porcelain

摘要

High strength porcelain having an unglazed bending strength of greater than 1,400 kg/cm.sup.2 and consisting essentially of 22-85% by weight of SiO.sub.2, 10-73% by weight of Al.sub.2 O.sub.3, and 1.5-6.5% by weight of K.sub.2 O and/or Na.sub.2 O. The porcelain has a total degree of crystallinity of more than 40% by weight, and a crystalline grain size of not greater than 20 m, and it is free from defects of larger than 40 . mu.m. The porcelain is produced by pulverizing a starting material mixture of quartz-feldspar-alumina system so that 85- 95% by weight of particles thereof have a grain size of not greater than 10 m, calcining the mixture, adding clay-mineral material therein, pulverizing so that the clay-mineral-added mixture contains less than 85% by weight of particles with a grain size of not greater than 10 m, forming, drying, and firing at 1,100-1,400 C.