酸素および窒素分圧の異なる溶接雰囲気中における溶接現象と溶接部の性質(その1)

ジルコニウム合金管の溶接に関する研究(第3報)

抄録

The purpose of this study is to investigate the influence of extremely low levels of oxygen and nitrogen partial pressure, Po₂ and PN₂ in TIG welding atmospheres on the welding phenomenon and properties of welds of zirconium alloy tubing.
In TIG welding of Zircaloy-2 tubing in welding atmospheres with various Po₂ and PN₂, the arc voltages were measured and the properties of welds (surface discoloration, oxygen and nitrogen contents) were examined.
Although definite arc voltage change is not observed at welding in ≤ 4.1 Pa of Po₂, a significant arc voltage drop with increase of PN₂ is observed at welding in 0.4-16.9 Pa of PN₂, and oxygen appears to inhibit this arc voltage drop.
The surface of weld metal and heat affected zone (HAZ) in the atmosphere of 0.1 Pa of Po₂ and 0.4 Pa of PN₂ remains bright.
The surface discoloration is observable slightly on weld metal and HAZ in the atmosphere of 1.1 Pa of Po₂, and with increase of Po₂ the initial straw color becomes darker until it gets partially blue.
No surface discoloration is observable on weld metals and HAZ in the atmospheres of PN₂ - 16.9 Pa with 0.1 Pa of Po₂.
The nitrogen content [N] in the weld metal increases linearly with increase of √PN₂ and the increasing rate of [N] in inner part of weld metal is lower than that of [N] in outer part.
The oxygen content [O] in the weld metal increases linearly with increase of √Po₂ and shows same relations as [N], although the values of [0] in the weld metals fluctuate more than [N].