Production of Al–Ti–B grain refining master alloys from B2O3 and K2TiF6

It is very desirable to replace the KBF4 salt in the popular “halide salt” process to reduce the volume of fluoride-bearing particulate material to be added to molten aluminium. Several practices all relying on B2O3 to supply B, were employed in the present work to produce Al–5Ti–1B grain refiners. Replacing the KBF4 salt in the halide salt process entirely with B2O3, has not only impaired the grain refining performance, but, with the dross generated, has also hurt the fluidity of the melt making pouring difficult. A significant improvement was noted both in the microstructural features and in the grain refining efficiency when B2O3 was pre-mixed with a drossing flux to promote the seperation of oxides from the molten alloy. However, this practice has almost completely negated the particulate material savings offered by B2O3. The Ti recovery and the grain refining efficiency achieved when B2O3 and KBF4 were used together to supply B, was nearly as good as when the latter was used alone. It is thus concluded that KBF4 can be replaced with B2O3, only partially, to take advantage of lower fluoride emissions and particulate material savings without a penalty in grain refining efficiency.