NITROGEN ABSORPTION OF STAINLESS STEEL WELD METAL IN PRESSURIZED WELDING ATMOSPHERES.

Type 304L stainless steel was welded with a 20% Cr-10% Ni stainless steel filler wire in pressurized N//2 and N//2-Ar atmospheres of 0. 1 to approximately 3 MPa. Effects of welding conditions and the nitrogen partial pressure on the nitrogen content of the stainless steel weld metal were systematically studied. In N//2 welding atmosphere, the nitrogen content of the weld metal decreases with increases in welding current and travel speed, and with a decrease in arc voltage. The nitrogen content of the weld metal increases with the nitrogen pressure, but the degree of the increase diminishes with the increase in the nitrogen pressure. The nitrogen absorption of weld metal does not obey Sieverts' law. In N//2-Ar welding atmosphere, when the nitrogen partial pressure is constant, the nitrogen content of weld metal in high pressure welding atmosphere is smaller than that in low pressure welding atmosphere. A discussion on the nitrogen absorption of weld metal with thermodynamic data suggests that the reaction time in welding process is too short for the nitrogen content of weld metal to reach the equilibrium value in high pressure atmosphere.