Castings with directional solidification - where empty moulds are heated to above m.pt. of metal to be cast, then filled and cooled from their bases

摘要

The entire surfaces of the moulds, including their bases, are heatedd to above the m.pt. of the metal to be cast, and the moulds are then filled with that metal. The filled moulds are conveyed through a crystallisation zone equipped with side heaters reduced stepwise towards the top of the moulds. In the crystallisation zone, the moulds rest on a cooled surface so solidification starts from the base of each mould and proceeds upwards as the moulds travel through the zone. The pref. plant consists of a furnace with heaters in its side walls, where heat is transferred to different vertical zones of the moulds, so the latter are heated and cooled stepwise in accordance with a program and the floor of the crystallisation zone is formed by a water-cooled box. Accurate control of temp. gradients in moulds, is achieved, so columnar crystal structures are obtd. Useful in mfr. of turbine blades or magnets etc.