A study on microstructural and mechanical properties of gas tungsten arc welded thick cryogenic 9% Ni alloy steel butt joint

Abstract

Low alloy steel plates containing 9% Ni are generally preferred in the production of LNG storage tanks, due to their outstanding combination of properties such as excellent toughness, high ductility and crack re-sistance at very low temperatures. Welding is an indispensable manufacturing method in the production of LNG storage tanks. Thus, there is a need for reliable welding procedures which do not diminish low tem-perature properties of this steel grade. This study introduces the result of microstructural evolution in the weld region and the mechanical properties of the gas tungsten arc welded 10 mm thick 9 Ni steel joint produced by using a Ni-based filler wire, which is widely used in LNG storage tanks. The microstructures evolved in the weld region were examined by extensive optical microscopy and SEM investigations. Mechanical properties and joint performance values of the welded joints were determined by detailed microhardness measurements and transverse tensile tests. Moreover, fracture toughness of the joint fab-ricated was also determined at - 196 degrees C by Charpy V-notch test. (c) 2021 CIRP.