Two characteristics, high basicity and high viscosity, are required for the anti-entrapment mould flux. However, it had been difficult to apply the high basicity and high viscosity mould flux for a round billet casting because of heat flux fluctuations in the mould.
We supposed that the heat flux fluctuations were caused by unstable crystallization of the flux film between the mould and the solidified shell. Assuming that the contaminating constituents which do not compose the main crystal phase bring the unstable crystallization of the flux film, we have researched an adequate main crystal for the high basicity and high viscosity mould flux which has proper composition and melting point. As a result, there was no proper single crystal, but we have found an adequate combination of two crystals, gehlenite and akermanite. These two crystals have similar constructions each other to make a solid solution, melilite. Melilite behaves as a single phase crystal as well as it can take any compositions between gehlenite and akermanite. These properties of melilite diminish restraints on mould flux design.
Consequently, we have successfully developed the anti-entrapment mould flux for the round billet casting, achieving a result to reduce mould flux defects effectively.
