Abstract: Porous silicon carbide bodies are obtained by starting with a powder of particle size falling within a single sieve mesh range fraction and consisting either entirely of carbon particles or a mixture of carbon and silicon carbide particles of the same mesh fraction is mixed or coated with 15 to 30% by weight of a binder, moulded to shape, warmed in the temperature range from 40.degree. to 200.degree. C. to vaporize volatile material and then coked at a temperature rising to 850.degree. C. Then it is siliconized by raising the temperature to the range from 1650.degree. to 1950.degree. C. with gaseous silicon or impregnated with silicon by dipping the body into a silicon melt and convert it to carbide, with the excess silicon thereafter being removed by vaporizing out or by boiling in lye. Sieve mesh fractions in the region of a few hundred .mu.m are preferred, and the density of the porous body after pressing but before siliconizing should lie in the neighborhood of 0.6 to 0.7 g/cm.sup.3.

Abstract: Component bodies of silicon carbide base material, at least in their surface layers, are welded together without the provision of a binder at finely polished joining surfaces by virtue of the fact that at least one of the joint surfaces is of a silicon carbide material containing an excess of silicon (SiSiC). The component bodies are kept closely fitted together especially by an additional pressing force of at least 0.1 kg/cm.sup.2 during a heating stage at atmospheric or lower pressure at a temperature in the range from 1500.degree. C. to 1800.degree. C. for 15 to 100 minutes in an inert atmosphere, the excess of silicon at the boundary making it possible for silicon carbide crystal growth to take place across the boundary.

Abstract: A significant improvement of the silicon impregnation depth of a carbon precursor body in the siliconizing thereof to make a silicon carbide body is obtained, as well as an accelerated conversion into silicon carbide if activated carbon is used in whole or in part as the carbon powder component of the precursor body. The molding material is preferably 20 to 60% by weight of binder and 20 to 70% activated carbon. This molding material may also usefully contain 10 to 60% by weight of .alpha.-silicon carbide, which may be previously made by siliconizing carbon powder.