Effect of welding heatinput on microstructure and properties of MAG welded joint for low nickel high nitrogen austenitic stainless steel

The laser-pulsed hybrid welding of 08Cr19MnNi3Cu2N austenitic stainless steel with low nickel and nitrogen content was carried out by using four kinds of shielding gases: 100% Ar, 98% Ar + 2% N₂, 92% Ar + 8% N₂ and 85% Ar + 15% N₂. The effects of nitrogen proportion in the shielding gas on the weld penetration width, microhardness, microstructure, arc characteristics and ferrite content were studied. The results shows that with the increase of nitrogen ratio, the number and volume of porosity increase, and which also can induced that the weld penetration become deeper remarkably and the weld width become narrower. The average microhardness of weld decreases and the arc column width decreases with the increase of nitrogen ratio. The weld spatter increases in number an volume, and the amount of welding fume increases gradually. The arc stability becomes poor with the increase of nitrogen content in the shielding gas. In addition, the ferrite content in the weld metal decreased from 6.91%, 6.80% to 5.38% and 4.62%, the ferrite dendrites also gradually became smaller, and the secondary dendrite arm became shorter. Only a small amount of δ and γ phases were found in the weld metal, and no σ phase and nitride were found to precipitate. The austenite grain size also decreased with the increase of nitrogen ratio from the four crystal planes.