The Nitrogen Absorption of Iron Weld Metal by Gas Tungsten Arc Welding

Abstract

Using an arc atmosphere controlling chamber, effects of the welding condition and atmosphere on the nitrogen content of the iron weld metal were investigated by gas tungsten arc welding. The results are as follows:
(1) The nitrogen content decreases with increasing the welding current.
(2) The nitrogen content hardly depends on the arc length and the travel speed.
(3) The nitrogen content is anomalously high at low arc atmospheric pressure region and constant above 0.2 atm of the nitrogen pressure in N₂ gas atmosphere (P_N2≤1 atm).
(4) The nitrogen content increases with increasing the nitrogen partial pressure and is constant above 0.1 atm of the nitrogen partial pressure in the N₂-Ar and N₂-He gas mixture atmospheres (P_N2+P_Ar=1atm, P_N2+P_He=1 atm).
(5) The nitrogen content gradually increases with increasing the nitrogen partial pressure in the N₂-H₂ gas mixture atmosphere (P_N2+P_H2=1 atm).
(6) The nitrogen absorption into weld metal was discussed with equilibrium data.