The BN normal pressure sintering ceramics null which is superior in

摘要

PURPOSE:To obtain the title ceramic consisting of BN no-pressure sintered crystals and having excellent melting flacture resistance to a melt such as metal and glass by regulating its fundamental components to specific ratio or above of BN and the balance one or more kinds of ceramic components selected from SiO2, AlN and the oxide of rare earth elements. CONSTITUTION:BN powder, =40%, contg. amorphous BN powder at least in a part and one or more kinds of ceramic components selected from the groups of SiO2, Al2O3, AlN, B4C, the oxide of rare earth elements, TiB2, ZrB2 and the oxide of alkaline earth metals are mixed to prepare the fundamental components. The mixture is then formed, e.g., into the bar shape by rubber pressing and is thereafter subjected to no-pressure sintering at 1800 deg.C in an N2 atmosphere to obtain the objective BN no-pressure sintered ceramic. The ceramic has the characteristics of repelling molten steel in particular, has extremely small melting flacture amt. and furthermore has high strength.