1994 Volume 12 Issue 3 Pages 386-389
The purpose of this study is to investigate the influence of extreamly low levels of oxygen and nitrogen partial pressure, PO2 and PN2 in pressurized 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 in total pressure (PT) of 0.32 MPa (optionally 0.55 MPa), 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 observable at welding in ≤ 12.9 Pa of PO2 and 15.6-67.2 Pa of PO2+N2 (PO2/PN2=1/4), a tendency bf arc voltage drop with increase of PN2 is observed at welding in 13.1-53.0 Pa of PN2 (PO2=0.3 Pa).
The surface of weld metal and heat affected zone (HAZ) in the atmosphere of 0.3 Pa of PO2 and 1.3 Pa of PN2 remains bright.
The surface discoloration is observable slightly on weld metal and HAZ in the atmosphere of 3.4 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≤53.0 Pa with 0.3 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 outer part of weld metal increases linearly with increase of √PO2 and shows same relations as [N], although the values of [O] in the weld metals flucutuate more than [N].
The increasing rates of [N] and [O] in the weld metal under PT=0.32 MPa are lower than that of [N] and [O] in the weld metal under PT=0.10 MPa which is reported in Report 3.
