Advanced Casting Technologies Using High Shear Melt Conditioning

Abstract In recent years BCAST has developed the high shear melt conditioning (HSMC) process for controlling solidification. HSMC is now an emerging technology to manipulate the solidification process by intensive shearing to control both the cast microstructure and defect formation. The high shear is applied to the melt using a simple rotor stator which has been demonstrated to disperse oxide films to provide a high density of oxide particles to enhance nucleation. The high-shear device has been successfully applied directly in the sump during DC casting up to the industrial scale to provide both significant grain refinement and uniform microstructure with reduced segregation and defects. It produces a DC casting sump with uniform chemical composition, uniform temperature, and a significantly increased temperature gradient at the solidification front. The sump temperature can be controlled by appropriate selection of the rotation speed. This provides the opportunity to control the cast microstructure, for example, to produce fine and uniformly dispersed second phase particles to improve mechanical properties. The high-shear device can also be used to degas alloys to unprecedentedly low hydrogen levels and has also been successfully applied to remove iron from casting alloys in which the iron containing particles are the primary solidification phase.