GB440296A - Improvements in and relating to methods of casting - Google Patents

Abstract

440,296. Moulding processes. AKERLUND, E. G., 7, Riddaregatan, and ELMQVIST, C., 5, Snickaregatan, both in Stockholm. Dec. 3, 1934, No. 34676. [Class 83 (i)] Patterns.-Metal castings are produced from a pattern by casting an elastic negative from glue material round the pattern, casting wax or other fusible material in the negative to form a hollow positive, casting a refractory core in the positive and a refractory mould about the positive, melting out the positive and replacing it by casting metal. The pattern 10 is first coated with a layer of clay 11 which is then surrounded by plaster of Paris 9 which may be removed in sections. The clay is removed and an elastic material is poured into the space between the pattern 10 and mould 9. The elastic material may comprise a mixture of glue or gelatine, glycerine and alum, in the proportions 93 per cent, 5 per cent, and 2 per cent by weight. The elastic negative is removed, if necessary by slitting, and is treated with alum, formic or tannic acid, &c. to toughen it. The negative is then replaced in the mould 9 and is coated internally with a material having a lower melting point than the negative. Thus wax may be poured into the negative and applied to the walls by rotation. The interior of the wax positive is filled with a fluid investment material 14, which hardens. A suitable material comprises plaster of Paris, pulverized quartz or sand, and aluminium silicate clay. The elastic negative is removed and supports 15 are inserted in the wax which is then encased in similar investment material 16. The entire assemblage is heated to 600‹ C., thus drying the investment and causing the wax to melt and run out through a vent 18. The space previously occupied by the wax is finally filled with molten metal and the investment removed. The supports 15 are pulled out and the surface of the cast is smoothed.