The pressure casting system permits high product volumes and reduces the unit cost of the casting. Nevertheless, producing “sound” castings fundamentally means using an alloy at the best of its technical-metallurgical characteristics. That is:
The process usually used for aluminium alloys is the so-called cold chamber process: the molten metal is pushed quickly by a piston into a die equipped with suitable vent channels and extractors.
Under pressure, the metal solidifies, creating an excellent casting – but which may not be suitable for following heat treatment due to hydrogen micro-porosity and oxide films. For this reason, it is necessary to remove as much hydrogen from the molten mass as possible, as well as eliminate the micro-porosity and oxides inevitably present, as they are the cause of discontinuity in the matrix, which influence, if not removed, the structural presence of the material and therefore the quality of the casting.