Casting metal shapes - involves metal drawn into mould by vacuum and then subjected to positive pressure

摘要

Molten metal is drawn upwards through one or more inlets into a mould in the process. A vacuum is applied so that the molten metal fills the mould and rises into at least one riser pipe. The metal in the inlets to the mould is caused to harden as soon as a required level in the riser has been reached, so that the molten metal is enclosed in the mould. The mould is then pressurised. The hardening of the metal in the inlet is produced by a redn. in the velocity, or a cessation, of the entry to the mould and is in the form of a slot whose width is less than that of the thinnest section of the shape being cast. The mould may be enclosed in a gas-tight cover for the application of the vacuum and pressurisation. USE/ADVANTAGE - Used in the casting of metal shapes for various uses. The molten metal is enclosed in the mould before it can harden, so that the application of an external pressure can be used to ensure that all of the mould is completely filled. No valves are used, thus making the process simple and economical, since it is difficult for valves to survive the temps. involved in the casting of molten metals.