Microstructure and cryogenic toughness of 316LN austenite stainless steel weld metal welded by NG-MAG arc welding

Abstract

Using narrow-gap Metal Active Gas (NG-MAG) arc welding, the low-temperature impact toughness and microstructures of the 316LN welded joints have been researched and characterized by Charpy impact test, optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that the low temperature toughness in the as-welded state is 132J and the toughness of the post-weld heat treatment was 112J. There are many dimples in the impact fracture, which indicated plastic fracture. The ferrite is located at the austenite grain boundary and exhibits a strip shape with a width of about 400 nm.