GB1370329A - Metal casting process - Google Patents

Abstract

1370329 Casting processes PRECISION METALSMITHS Inc 7 Dec 1971 [9 Dec 1970 28 May 1971] 56757/71 Heading B3F A method of casting metal in a gas-permeable mould 120 comprises applying a vacuum to the opening 122 of the mould, introducing molten metal under vacuum into the mould through said opening, increasing the pressure on the metal in the mould, and applying a vacuum to the outside of the mould prior to solidification of the metal. The increased pressure applied to the metal in the mould may be provided by releasing the vacuum applied to the opening of the mould. The mould 120 is located in a housing 18 secured to a framework 15. A second housing 19 provided with wheels 47 is movable along rails 40 between a position above the housing 18 and the broken line position shown in Fig. 1. The rails 40 are pivoted at one end to the framework 15 and at their other end are connected to a piston and cylinder unit 44 which is used to raise and lower the rails. When the rails are in their lowered position the housing 19 engages the housing 18 to form a sealed enclosure having a pouring chamber 65 and a mould chamber 66, the two chambers being isolated from one another. The mould is contained within a perforated flask 128 and is located on a metal plate 72 provided with a gasket 73. A refractory core is positioned within a mould passage 123. The pouring chamber 65 is provided with a laddle 95 which may be tilted by an external handle 102 and filled through an opening 103 in the housing 19. In operation, the mould is placed in the housing 18, the housing 19 moved into engagement with the latter, both chambers 65 and 66 are evacuated, the metal is poured from the ladle 95 into the mould, and the vacuum is released in the chamber 65 whilst maintaining the vacuum in the chamber 66 during at least partial solidification of the metal. When casting an aluminium alloy, the mould may be preheated to between 300‹ and 800‹ F. and the metal poured at 1300‹ F. In a modification, Fig. 6 (not shown), two lower housings are provided, the upper housing being moved into engagement with each alternately. An induction melting furnace may be provided in the pouring chamber instead of a ladle.