Influence of shielding gas on microstructure and properties of K-TIG welded 304N stainless steel

304N stainless steel plate with 13.5 mm in thickness was butt welded by K-TIG without groove. The chemical components，microstructures and properties of butt welded joint were studied by SEM, XRD, 3D measuring laser microscope, hardness tester. The experimental results indicate that the N-content in the weld metal reduces by 18%, the ferrite content of weld metal increases by 20 times, and the hardness of weld decreases by 15%, compared with that of base material when pure Ar gas is used as the shielding gas. The N-content in weld metal increases by 90%, the ferrite content of weld metal reduces by 84%, and the hardness of weld increases by 14% at least when the shielding gas is the mixture of Ar + 3%N2.