The development and prevention of channel segregation during alloy solidification

摘要

This research began on the simple premise that since channel segregation is a consequence of natural convection ('thermo-solutal' or 'thermo-haline') suitable mold movement during the course of alloy solidification should prevent or reduce the incidence of well-defined channels ('A' segregation or 'freckles'). The initial idea proved to be correct. It was demonstrated that with a slow (less than 10 rpm) precession about an inclined axis (approximately 30 deg to vertical) base chilled castings of the transparent NH4ClH2O analogue solidify without the usual chemical segregation. It was subsequently shown that the same was true of metal ingots, using the Pb-Sn system and, indeed, that here was simple method of preventing channel or freckle formation.