Gas tungsten arc welding of vanadium alloys with impurity control

Gas tungsten arc welding in vanadium alloys is controlled by interstitial impurities. Techniques have been developed to weld V–4Cr–4Ti in a high-purity argon atmosphere resulting in a DBTT of −20 °C. The atmosphere was controlled by a Zr–Al getter which is activated at high temperature to obtain a clean surface then cooled and allowed to absorb hydrogen and oxygen impurities. Through the use of low-oxygen base metal and high-purity weld filler wire, a DBTT of −145 °C was obtained. Experiments using electron beam welding have shown that grain size also has an important effect on weld ductility. Introduction of nitrogen and yttrium has been used to study their effect on grain size. Using a combination of atmosphere control, alloy purity control, and grain size control, it is anticipated that V–Cr–Ti alloys will be weldable in field conditions.