Use of Nitrogen in Welding Atmosphere (Report 2)

Abstract

Nitrogen was intentionally alloyed to the stainless steel weld metals by shielding gas containing nitrogen of MIG welding. Nitrogen contents, mechanical properties and corrosion rate of weld metals were examined and the following results were obtained:
(1) Nitrogen content of weld metal increased with the increase of nitrogen content of shielding gas. CO₂-N₂ shielding gas gave the higher nitrogen content into the weld metal than Ar-N₂ shielding gas.
(2) Nitrogen content of weld metal generally decreased with the increase of welding current. On the higher current welding of a nitrogen alloyed stainless steel (0.2%N) by the same electrode wire, however, nitrogen content of weld metal remained unvaried under the increasing nitrogen content of shielding gas.
(3) Weld metal strength increased lineally with the increase of its nitrogen content, accompanied with a little decrease of ductility at room temperature and 500°C. The same increase of strength was observed at 700°C, but ductility drop was remarkable.
(4) The general corrosion of weld metal accelerated lineally with the increase of amount of nitride. However, the influence of nitride on the intergranullar corrosion seemed to be not essential.