Connect, November/December 1998
A fundamentally new approach to centrifugal continuous casting/extrusion (CCCe) is under development at TWI.
This technique appears to provide an alternative, and in some cases unique, process for continuous casting difficult-to-extrude materials such as hardfacing alloy welding consumables, superconductor, intermetallics, metal-matrix composites and fibre-optic cables. It may also prove highly suitable for the manufacture of strip.
Fig.1 Centrifugal continuous casting/extrusion: comprising an outer container rotated at a fractionally lower rotational speed than the inner rotating casting arms to produce a double helical coil of rod
As shown in Fig. 1, the centrifugal technique develops forces in the liquid material which increase progressively as it moves from the central feed region to the extremities of the arms. Fig. 2 illustrates the single arm variant.
Unlike existing techniques, CCCe produces a gradual transition in the level of centrifugal force thus avoiding discontinuities. Essentially, as the material is cooled along the arms of the centrifuge, a higher centrifugal force correspondingly acts upon the material and, where the material is liquid or deformable at the centre, the centrifugal force is lower.
The outer drum rotates to provide a receiving at a suitable speed.
It is believed that the CCCe product will have no gravity segregation effects as found in conventional centrifugal casting. The movement of the material along the centrifuge arm is at a speed that cancels out these effects. Also the greater ferrostatic pressure during solidification minimises many existing solidification problems.
TWI has filed a patent for some aspects of the technique but organisations interested in taking part in a collaborative feasibility project to develop this cutting edge process should contact Martin Ogle or Roger Wise.
For more information please contact us.