Strain Effect On Microstructural Properties Of SUS 304L Joint By PAW+GTAW

Abstract

304L stainless steel was joined by a combination welding process of plasma arc welding and gas tungsten arc welding (PAW + GTAW). Then pre-strain treatment on 304L welded joint by 9% was carried out using uniaxial static tensile at room temperature. Effect of strain on microstructure evolution in joint was analyzed by field emission scanning electron microscope (FESEM) and on mechanical properties was also studied. The results indicated that the strain rate of 304L joint showed inhomogeneity including 3% in the weld metal and 13% in the heat affected zone (HAZ), which induced martensitic transformation occurring in HAZ. Tensile strength of the joint increased from 700MPa as welded to 804MPa after strain at room temperature and it reached 1700MPa from 1480MPa at low temperature of -196℃. Impact toughness in HAZ was the least among the whole joint, but it was still 94J at -196℃after strain. The fracture surface showed large numbered of cleavage steps with elongated parabolic dimples.