BODY COMPOSITION FOR LARGE-SIZED PORCELAIN AND PRODUCTION OF LARGE-SIZED PORCELAIN

摘要

PURPOSE:To decrease the cracking at the time of production of thin type large-sized porcelain in a roller hearth kiln and to allow efficient production by constituting essential components of specific ratios of clay, pottery stone, wollastonite, and cordierite. CONSTITUTION:The large-sized porcelain is obtd. by shaping the body compsn. for porcelain essentially consisting, by weight %, of 20 to 50 clay, 10 to 40 pottery stone, 5 to 25 wollastonite, and 3 to 10 cordierite, then drying and firing the shaped body in the roller hearth kiln. The shaping property and sinterability of the clay are poor if the ratio thereof is below the lower limit and the deformation at the time of the firing increases if the ratio exceeds the upper limit. The pottery stone requires the high-temp. firing for porcelainization to low moisture absorbance and increases deformation if the ratio is below the lower limit. The coefft. of thermal expansion near the silica transformation point increases and the cracking arises frequently in the cooling process after the firing if the ratio exceeds the upper limit. The strength holding effect of the wollastonite is low if the ratio thereof is below the lower limit and the cracking arises frequently in the cooling process if the ratio exceeds the upper limit. The cracking arises frequently if the ratio of the cordierite is below the lower limit and the high-temp. firing is required for the porcelainization to low moisture absorbance if the ratio is above the upper limit.