Comparison of impact property of Japanese and US reference heats of V-4Cr-4Ti after gas-tungsten-arc welding

Charpy impact tests of Japanese and US reference V-4Cr-4Ti alloys, NIFS-HEA T-1 (180 wppm oxygen) and US832665 (310 wppm Oxygen), were examined after g as-tungsten-are (GTA) welding in a purified argon atmosphere. To investigat e the effects of further reduction of oxygen level in the fusion zone, fill er wires made of HP thigh-purity V-4Cr-4Ti, 36 wppm oxygen) were used as we ll as those made of the reference alloys. Charpy impact property of NIFS-HE AT-1 in as-CTA-welded condition was superior to that of US832665. Use of th e high-purity filler wires improved the impact property further. Good corre lation was obtained between ductile-brittle-transition temperature (DBTT) a nd the oxygen level in the fusion zone. Since oxygen contamination from the atmosphere is avoidable by controlling its impurity level, oxygen reductio n in weld materials, such as plate and wire, is crucial to obtain good weld ability. Only contamination element detected in this study was hydrogen. Co ntamination occurred not only in fusion zone but also in base metal. Degass ing of hydrogen after the welding may improve the impact property further.