Patent ID: 7121319

Claim:
A metal flow system, for use in pressure casting of magnesium alloy in a pressure casting machine selected from hot chamber and cold chamber die casting machines and having a supply of molten magnesium alloy and a mould or die which defines a die cavity; wherein the metal flow system includes a die or mould tool means which defines: (I) a runner adapted for receiving molten magnesium alloy under pressure from the supply of the pressure casting machine, and (ii) a controlled expansion region through which alloy received from the runner is able to pass before being injected through a gate defining an inlet to the die cavity; wherein the flow system has a form providing for control of alloy flow velocities therein, said form of the flow system comprising: (I) an effective cross-sectional area of the runner for determining the flow velocity of alloy received under pressure therein from the supply of the pressure casting machine; and (ii) a form of said expansion region which enables alloy flow therein to spread laterally, with respect to its direction of injection, and thereby undergo a reduction in flow velocity in the expansion region relative to the alloy flow velocity in the runner such that said flow velocity in the runner and said reduction in flow velocity in the expansion region change the state of the alloy from a molten state in the runner into a semi-solid state for flow through the gate and into the die cavity.