Vacuum Induction Melting of Ti-6AI-4V in a Cold Crucible

摘要

The effect of fluoride inclusions on the properties of titanium produced from the Bureau of Mines-developed induction slag melting process is of concern to the titanium industry. The objective of the research was to determine the effect of removing the nonconductive molten calcium fluoride (CaF2) slag used as an insulator between the titanium and the segmented copper crucible. The data were obtained from single-induction-melted ingots prepared with no CaF2 insulating slag and an ingot prepared with the normal addition of 4 percent CaF2 slag. The results showed that the mechanical properties of single-induction-slag-melted and annealed Ti-6Al-4V alloy exceed the minimum values specified in 'Aerospace Materials Specification for Titanium Alloy Bars and Forgings AMS4928H.' High-cycle, tension-tension fatigue testing yielded similar results. The data from 44 of the 45 specimens were contained within the typical scatter band for fatigue data on wrought Ti-6Al-4V alloy. Although the removal of the insulating slag is a desirable change, the data from the specimens with the previously standard 4 percent slag addition showed no detrimental effect from the slag inclusions.