Patent ID: 7111663

Claim:
A metal flow system for high pressure die casting of alloys using a machine having a pressurised source of molten alloy and a mould defining at least one die cavity, wherein the system defines a metal flow path by which alloy received from the pressurised source is able to flow into the die cavity, wherein: (a) a first part of the length of the flow path includes a runner and a controlled expansion port (CEP) which increases in cross-sectional area, in the direction of alloy flow therethrough, from an inlet end of the CEP at an outlet end of the runner to an outlet end of the CEP; and (b) a CEP exit module (CEM) which forms a second part of the length of the flow path from the outlet end of the CEP; and wherein the increase in cross-sectional area of the CEP is such that molten alloy, received at the CEP inlet end at a sufficient flow velocity, undergoes a reduction in flow velocity in its flow through the CEP whereby the alloy is caused to change from a molten state to a semi-solid state, and wherein the CEM has a form which controls the alloy flow whereby the alloy flow velocity decreases progressively from the level at the outlet end of the CEP whereby, at the location at which the flow path communicates with the die cavity, the alloy flow velocity is at a level significantly below the level at the outlet end of the CEP, such that the change in state generated in the CEP is maintained substantially throughout filling of the die cavity and such that the alloy is able to undergo rapid solidification in the die cavity and back along the flow path towards the CEP.