GB563358A - Method and means for forming metal castings - Google Patents

Abstract

563,358. Moulds. CASTINGS PATENT CORPORATION. Feb. 1, 1943, No. 1682. Convention date, April 8, 1942. [Class 83 (i)] The rate of cooling of each part of a casting 10 is controlled to ensure a desired rate of cooling and direction of movement of the zone of solidification by using a mould comprising a highly conductive shell 14, 16 lined with a low conductive investment 4, the thickness of the lining being varied to give the desired result. The part of the casting desired to solidify first may make direct contact with the shell, i.e. at 32. A shrink bob 27 may be provided for each casting and these may be arranged and connected to the sprue 5 as described in Specifications 546,906 and 546,991. The lining may comprise separately moulded blocks made from calcined gypsum, asbestos fibre, and water, the major portion of the water being subsequently removed to increase porosity. The shell is of high heat-absorbing capacity, e.g. metal, is varied in thickness, and is vented at 24. Casting processes.-If, owing to the complicated form of the article 40, Fig. 3, required and the alloy cast, e.g. beryllium copper, it is impossible to obtain a part 42 free from defects, this part may be cast thicker, as at 52, and the excess, which contains the defects, is subsequently removed by machining.