Comalco Aluminum Limited

Comalco Aluminium Limited

Rodney A Legge

John A Eady

Joseph R Ponteri

Rodney E Proposch

Christopher J Heathcock

Kevin P Rogers

Peter L Kean

A mould assembly comprising mould segments of generally non-thermally conductive material which define a mould cavity is upwardly filled with liquid metal through at least one in-gate. A thermal extraction member of a high thermally conductive material contacts a portion of the mould cavity through which heat is extracted rapidly to establish positive thermal gradients in the casting and thereby promote directional solidification. The mould assembly is also provided with a seal to selectively isolate the mould assembly from the liquid metal source to allow the mould assembly to be removed from the casting station and transferred to the cooling station, providing a more efficient use of the casting station. In addition, once a shell has solidified then the mould segments and metal contained therein can be transferred to the cooling station.

Casting of metal objects

The mould assembly comprises mould segments of generally non-thermally conductive material which define a mould cavity for receiving liquid metal through at least one in-gate. A thermal extraction member of a high thermally conductive material contacts a portion of the mould cavity through which heat can be extracted rapidly to establish positive thermal gradients in the casting and thereby promote directional solidification. The mould assembly is also provided with a seal to selectively isolate the mould assembly from the liquid metal source to allow the mould assembly to be removed from the casting station to the cooling station before any substantial solidification has occurred, providing a more efficient use of the casting station.

A cast hypereutectic Al-Si alloy with from 12-15% Si, having excellent wear resistance and machinability, improved fatigue strength and good levels of ambient and elevated temperature properties is provided, as well as a method of producing such alloy. The alloy and a melt used in the method contains Sr in excess of 0.10% and Ti in excess of 0.005%, the alloy further comprising: Cu 1.5 to 5.5%, Ni 1.0 to 3.00%, Mg 0.1 to 1.0%, Fe 0.1 to 1.0%, Mn 0.1 to 0.8%, Zr 0.01 to 0.1%, Zn 0 to 3.0%, Sn 0 to 0.2%, Pb 0 to 0.2%, Cr 0 to 0.1%, Na 0 to 0.01%, B (elemental) 0.05% maximum, Ca 0.003% maximum, P 0.003% maximum. Others 0.05 maximum each, the balance, apart from incidental impurities, being Al. The level of Sr in excess of 0.10% and Ti in excess of 0.005% is such that the alloy has a microstructure in which any primary Si formed is substantially uniformly dispersed and is substantially free of segregation, and in which substantially uniformly dispersed Sr intermetallic particles are present but are substantially free of such particles in the form of platelets, with the microstructure predominantly comprising a eutectic matrix.

Growing community of inventors

Woodend, Australia

Rodney A Legge