GB1191037A - Forming Holes in Hot Pressed Articles - Google Patents

Abstract

1,191,037. Hot press moulding of refractories. NORTON CO. 6 Aug., 1968 [7 Aug., 1967], No. 37504/68. Heading B5A. [Also in Divisions C1 and C7. Hard refractory compounds are moulded to high density articles by the hot pressing thereof, and are formed with a hole therethrough or a cavity therein by incorporating a removable insert of a mixture of carbon, e.g. graphite powder, with a hard refractory compound powder having at least as high a coefficient of thermal expansion as the refractory of the article and a melting point above the hot pressing temperature, the insert being removed by sand blasting. The refractory of the article may comprise Al 2 O 3 , B 4 C, TiB 2 , TiC, ZrO 2 , for which insert mixtures are specified comprising graphite with the same refractory or a mixture thereof with a different refractory. The article refractory and the insert mixture preferably incorporate a binder, e.g. wax. The article and the insert may both be separately preformed prior to the hot pressing. Alternatively the article refractory may be disposed around the insert prior to the hot pressing. An example is given wherein the article and insert are respectively preformed, with wax binder, from boron carbide, and a mixture of 50% B 4 C and 50% C. The assembly is hot pressed at 1000 to 2000 p.s.i. at 2200‹ C. for 5 minutes within a graphite mould coated with a mould release agent comprising flake graphite slurry in a polyethylene glycol/methylene chloride vehicle.