| 摘要 |
PURPOSE:To improve chemical durability, abrasion resistance, rolling life, etc., of a sintered silicon nitride by mixing a raw Si3N4 with a sintering additive in a specified proportion, and calcining after crushing, granulating, and molding said mixture. CONSTITUTION:(A) Si3N4 powder, (B) at least one kind of sintering additive selected from oxides of rare earth elements, ZrO2, oxides of alkaline earth metals, and Al2O3 are mixed in a proportion that a weight ratio of a sum or a content of SiO2 in the component (A) and a content of SiO2 in the component (B) to the content of metal oxides other than SiO2 in the component (B) is 1:4-4:1. The mixture is then crushed, granulated, and then dried forcibly, and a molded body is obtd. by molding the dried product. Then, the molded body is calcined primarily at 1,400-1,600 deg.C in N2 atmosphere under normal pressure, then pressed hydrostatically at 1,500-1,900 deg.C in N2 atmosphere under 200-1,700atm. Thus a highly dense sintered Si3N4 having <=0.5% porosity, >=15Gpa Knoop hardness (300g load), and 4:1-1:4 ratio of SiO2 in grain boundary glass phase compsn. to metal oxides other than SiO2, is obtd. |
