Abstract
In order to clarify the dissolving aspects of refractory elements (Ta, Mo, V) which are components of beta titanium alloys, the experiments of VAR with a mold of 100 mm diameter were carried out. In the experiments, the initial diameters of those elements were changed and their particles were observed after melting. Then, the experimental results were discussed by the mathematical model for dissolving. The following results were obtained.
(1) In the case of Ta, the dissolving was complete by the single VAR in the size of the initial particles under 200 mesh (74 μm), while in the case of Mo, the dissolving was complete under 100 mesh (149 μm). In the case of V, the dissolving was complete even under 6 mesh (3 360 μm).
(2) In the case of V, the dissolving was almost finished in the molten layer at the electrode top. But, in the case of Ta and Mo, the dissolving mainly made progress in the molten metal pool of ingot.
(3) The mathematical model well explained the experimental results, and the time needed for complete dissolving (tN) obtained by this analysis is thought to be an index of difficulty of the dissolving.
(4) The dissolving time in the molten metal pool was estimated. Compared with tN, it was found out that there exists the critical value of the initial diameter of refractory element for the complete dissolving. It is advisable that the initial diameter close to this critical value should be chosen even in a larger scale of VAR than that of these experiments.
