| 摘要 |
PURPOSE:To obtain moldings having excellent dimensional accuracy, good surface roughness and specific rates of nitriding in moldings of Si3N4 sintered after reaction by specifying the rate of packing of Si in the molding stage, the initial reaction temp. with the N2 of the moldings and the heating rate and temp. thereafter. CONSTITUTION:This molding is a molding of Si3N4 contg. metallic Si wherein 20-80% of metallic Si is converted to Si3N4. In order to obtain the same, fine powder of Si is so packed as to contain >=64vol% of the molding and is molded to the molding. If the ratio is <64%, the dimensional accuracy is not kept and deformation arises in the heating stage of removing the binder. The molding is sintered after the removal of the binder and at this time the molding is brought into contact with N2 at 1,000-1,100 deg.C to convert the surface of Si particles to Si3N4 to prevent the sintering of the Si particles, whereby high dimensional accuracy is obtained. Further the molding is heated to intensify strength, wherein the molding is heated to 1,200-1,380 deg.C at <=20 deg.C/hr heating rate under repetition of contact with N2 or holding in a vacuum and introducing of N2. When the heating rate exceeds the above-mentioned limit, surface smoothness is lost by spheroidal deposition of Si. Within the above-described temp. range, the rate of conversion to Si3N4 is maintained at necessary and sufficient rate, i.e. 20-80%. |
