Patent GB-1071185-A (GB)
Title: Improvements relating to refractories
IPC: C04B35/10
Filed: 1964-07-10
Abstract: A sintered refractory body is made by sintering in an oxidizing atmosphere a powder mixture comprising by weight 10-50% of Al or an Al base alloy of minus 80 mesh and 50-90% of refractory particles, at least half being minus 140 mesh, consisting of one or more of the carbides of Al, B, Si, Ti and W; the nitrides of Al, B, Ti, U, Si and Zr; and the borides of Cr, Mo, Ti, W, Si and Zr; the mixture being formed into a compact having a porosity of at least 20% and the sintering being effected between 600 DEG C. and the melting temperature of the refractory particles for a sufficient time to oxidize at least 90% of the Al. The mixture may also contain 0.2-10%, based on the Al, of a fluxing agent such as oxides of alkali metals, alkaline earth metals, V, Cr, Mo, W, Cu, Ag, Zn, Sb, and Bi, acetates, benzoates, bisulphates, bisulphites, bromates, nitrates, silicates, sulphates, sulphites and thiosulphates of the above metals, trialkyl tin oxide and lead silicate.  0.1-2% of a binder such as water, ethyl alcohol, ethylene glycol, acetone, carboxymethyl cellulose, rubber, gum arabic, naphthalene, polyvinyl alcohol, gums, glue and cement may also be added.  Sintering is carried out in air, oxygen or a mixture of oxygen and an inert gas and is controlled so that the refractory temperature does not exceed the furnace temperature by more than 100 DEG C.  The preferred fired refractory contains 35-83% SiC which is bonded by a crystalline matrix of Al2O3 and mullite having a porosity of 20-50% and containing cells 0.4-5 mils in diameter.ALSO:A sintered refractory body is made by sintering in an oxidizing atmosphere a powder mixture comprising by weight 10-50% of Al or an Al base alloy of minus 80 mesh and 50-90% of refractory particles, at least half being minus 140 mesh, consisting of one or more of the carbides of Al, B, Si, Ti and W; the nitrides of Al, B, Ti, U, Si and Zr; and the borides of Cr, Mo, Ti, W, Si and Zr; the mixture being formed into a compact having a porosity of at least 20% and the sintering being between 600 DEG  C. and the melting temperature of the refractory particles for a sufficient time to oxidize at least 90% of the Al.  The mixture may also contain 0.2-10%, based on the Al, of a fluxing agent such as oxides of alkali metals, alkaline earth metals, V, Cr, Mo, W, Cu, Ag, Zn, Sb, and Bi, acetates, benzoates, bisulphates, bisulphites, bromates, nitrates, silicates, sulphates, sulphites and thiosulphates of the above metals, trialkyl tin oxide and lead silicate.  0.1-2% of a binder such as water, ethyl alcohol, ethylene glycol, acetone, carboxymethyl cellulose, rubber, gum arabic, naphthalene, polyvinyl alcohol, gums, glue and cement may also be added.  Sintering is carried out in air, oxygen or a mixture of oxygen and an inert gas and is controlled so that the refractory temperature does not exceed the furnace temperature by more than 100 DEG  C.  The preferred fired refractory contains 35-83% SiC which is bonded by a crystalline matrix of Al2O3 and mullite having a porosity of 20-50% and containing cells 0.4-5 mils in diameter.