GB461104A - Process for the manufacture of precision castings from metals and alloys of high melting point - Google Patents

Abstract

461,104. Mould materials; moulding processes. KROSTA, V. May 22, 1936, Nos. 14457, 14458, and 14459. Convention dates, May 25, 1935, Feb. 20, 1936, and Feb. 20, 1936. [Class 83 (i)] In order to compensate for the shrinkage, on cooling, of castings of metals of the iron group and alloys thereof with metals of the third to the sixth group of the Periodic System and melting at 1000 to 1600‹ C. the mould is made entirely or chiefly of #-quartz and is heated, before pouring, so that the quartz is converted into tridymite or cristobalite thus causing the mould to expand. The amount of expansion can be varied according to the size of grain and origin of the quartz used, i.e. quartzite, kieselguhr, precipitated silica; so called silicious materials &c. or by adding catalysts, such as tungsten trioxide or phosphates, borates, silicofluorides, or already formed tridymite or cristobalite. The silica may be mixed with binders such as quartz ground to colloidal form, water glass which also acts as a catalyst, glue, dextrin and mastic or colophony dissolved in carbon tetrachloride. The moulds are heated in muffles of silicon-carbide. To prevent any chemical action between the mould and the cast metal or oxide thereon, substances of the same composition as those which might be formed by such action or substances which furnish the same reaction product on heating, are added to the mould material or the mould is not heated so highly, e.g. an alloy containing 70 per cent of nickel and 30 of chromium is cast in a mould at 700-800‹ C.