NITROGEN ABSORPTION OF IRON WELD METAL DURING GAS TUNGSTEN ARC WELDING.

Effects of welding conditions and welding atmospheres on the nitrogen absorption of iron weld metal containing quite low contents of impurity elements during gas tungsten arc welding were studied by using an arc atmosphere-controlling chamber. The nitrogen content of the weld metal decreases with an increase of the welding current, but scarcely depends on the arc length, the arc voltage and the travel speed. In N//2 gas atmosphere, the nitrogen content is extremely high at low atmospheric pressure. In both N//2-Ar and N//2-He gas mixture atmospheres, the nitrogen content increases with the nitrogen partial pressure (P//N//2) at low P//N//2 and is constant above P//N//2 of 0. 005 MPa. In N//2-H//2 gas mixture atmosphere, the nitrogen content increases gradually with P//N//2, but is lower than in the other atmospheres. The nitrogen content in all of the atmospheres does not obey Sieverts' law. The nitrogen absorption of iron weld metal was discussed with equilibrium data.