• Pericleous, Koulis
• Bojarevics, Valdis
• Roberts, R. J.
• Keough, G.
• Harding, R. A.
• Wickins, M.

Abstract

Induction Skull Melting (ISM) is widely used for melting reactive materials such as titanium-based alloys prior to casting. Although the water-cooled copper crucible avoids contamination, it produces a low superheat which is compensated for by pouring the metal at high speed into the mould. However, this often results in entrainment defects, such as bubbles. The University of Greenwich (UK) has developed a computer model of the ISM process which simulates the coupled influences of turbulent flow, heat transfer with phase change, and magneto-hydrodynamics. The model has predicted that the superimposition of a strong DC field on top of the normal AC field would reduce the turbulent stirring in the liquid metal, thereby reducing the heat loss through the base of the crucible and increasing the superheat. Consarc Corporation (USA) has developed the technology to apply a DC field to an ISM furnace at the University of Birmingham (UK). Research to measure the resulting increase of superheat has confirmed the computer predictions and showed that the addition of a DC field increased the superheat in molten TiAl from ∼45°C (AC field only) to ∼81°C (DC + AC fields). A similar increase in superheat was also measured when melting commercial purity titanium.

Topics

• impedance spectroscopy
• phase
• reactive
• copper
• defect
• casting
• titanium