Abstract
To grasp the characteristics on TIG weld joints of Zircaloy-2 tubing, the properties of weld heat affected zone (HAZ) welded in welding atmospheres with extremely low level of oxygen and nitrogen partial pressures, PO2 and PN2 were examined as compared to weld metals.
The original fine structures of Zircaloy-2 tubing are re-crystallized at heated zones to β phase and α+β phase range, and the grains grow gradually from end of HAZ to fusion boundary.
The nitrogen content [N] in outer part of HAZ increases linearly with increase of √PN2 as same as weld metals and the increasing rate of [N] is higher at nearer portion (0-1 mm) to fusion boundary than that of next portion (1-2 mm).
[N] in inner part of HAZ does not increase even in case of welding in atmospheres with higher PN2 (PN2=53.3 Pa) and also at the nearer portion (0-1 mm) to fusion boundary.
Although the oxygen content [O] in HAZ increases in case of welding in atmosphere with higher PO2 (PO2=13.9 Pa), the values of [O] in HAZ fluctuate more than [N], as weld metals, and definite relations between PO2 and [O] in HAZ were not obtainable.
