This invention relates to the casting of light metals such as aluminium or magnesium and their alloys.
Light metals such as aluminium or magnesium and their alloys are usually cast in the form of fabrication ingots which are then further worked, for example by rolling or extrusion. Such ingots are usually produced by the vertical, semi-continuous, direct chill (DC) method. This method was developed between forty and fifty years ago and produces higher quality and cheaper castings than had previously been possible using permanent moulds.
It is likely that in the earlier years of DC casting the operation was performed above ground level although it has not been established that it was; this would have presented two disadvantages, firstly there was a practical limit to the length of fabrication ingots that could be produced and secondly, if a "run-out" from the mould occurred, large quantities of molten metal falling from a considerable height could be distributed over a wide area with consequent danger to personnel and damage to plant.