Conventional die castings can be made stronger using a dynamic gating system and a runner system developed at CSIRO.
The researchers who developed the systems claim that they produce high-integrity castings with fine-grained microstructure and low porosity by improving the feed of molten metal into the casting. Both are suitable for use with aluminium and magnesium alloys.
’This is accomplished by influencing the flow behaviour of the molten metal, the fill pattern of the die and the subsequent solidification,’ said Dr Rob O’Donnell, the leader of CSIRO’s research team of metallurgists and casting engineers.
’Our researchers realised that, by changing the way in which molten metal is delivered to the die, we could take advantage of the high pressure inherent in the process to make castings with finer microstructure and lower porosity,’ said O’Donnell.
The researchers manufactured high-quality castings by changing the architecture of the runners (the passages along which molten metal flows into the die) and the gate (the narrow opening to the die cavity). The dynamic gating system incorporates a gate capable of changing its size in response to the pressure of the melt during filling.
’Our improved melt delivery systems are cost effective, can be used with existing casting machines and can significantly reduce the mass of the metal runner, wasting less metal,’ added O’Donnell.
Gases captured during the passage of the molten metal into the die cavity cause porosity, which, together with voids created during solidification, reduces the quality of the casting. Die castings with low porosity are stronger and can be successfully heat treated post casting to improve their mechanical properties.
The x-ray analysis of test castings showed a significant improvement in density in both thicker and thinner areas of the casting when the dynamic gate was used.
CSIRO is seeking commercial partners interested in licensing the systems.