NITROGEN ABSORPTION OF IRON WELD METAL IN PRESSURIZED WELDING ATMOSPHERES.

A purified iron was pressurized N//2 and N//2-Ar atmospheres of 0. 1 to about 3 MPa. In N//2 welding atmosphere, the nitrogen content of the weld metal decreases with an increase in welding current and a decrease in arc voltage and travel speed. The nitrogen content increases with nitrogen pressure, but the degree of increase diminishes with an increase in nitrogen pressure. The nitrogen absorption does not obey Sieverts' law. In N//2-Ar welding atmosphere when nitrogen partial pressure is constant, the nitrogen content of weld metal in high pressure welding atmosphere is smaller than that in low pressure atmosphere. A discussion on nitrogen absorption with thermodynamic data suggests that the reaction time in welding is too short for the nitrogen content to reach the equilibrium value in high pressure atmosphere.