Heat transfer characteristics in centrifuge melt-spinning

Centrifuge melt-spinning (CMS) is a new technique for the production of rapidly solidified metallic ribbons. In CMS, centrifugal forces are used twice: to eject the liquid melt on to the quenching substrate (a copper rim) by rotation of the casting crucible, and to ensure prolonged contact of the solidifying ribbon with the heat extraction sink by making the quenching rim rotate too, in the opposite direction. The heat transport in CMS has a Newtonian nature, as it can be considered as a constant-resistance heat transfer process. Calculated heat transfer coefficients h range between (1.55 to 4.30)×10^–6 W m^–2 sec^–1, a half to one order of magnitude higher than for conventional melt-spinning. Increasing the ejection pressure from 1.8 to 269 kPa causes the apparent heat transfer coefficient to increase by a factor of three. Conversely to conventional melt-spinning, two additional phenomena contribute to the heat transfer characteristics in CMS at high extraction velocities: forced convection and mechanical dragging of the melt. The overall effect is a net improvement of the heat transfer ability in CMS as compared to conventional melt-spinning.