Microstructure and Mechanical Properties of GTAW Welded Joint of Invar Alloy

Abstract

Experiment of automatic gas tungsten arc welding of liquefied natural gas carrier Invar alloy with a thickness of .7 mm was completed, and the welding parameters were optimized, as well as microstructure and mechanical properties of the welded joint were measured and analyzed. The grain size of the area near the weld centerline was small, mainly cellular dendrites, and the grain size on both sides of the weld centerline increased gradually, mainly dendrites, whereas the grain size near fusion line was larger, and there were more columnar crystals. The heat-affected zone was composed of coarse austenite grains. Transgranular cracks were the main cracks in the welding seam. When welding current was 40 A, frequency was 120 Hz, and welding speed was 350 mm/min, tensile strength of the welded joint was 446.9 MPa, which 88.1% of the base metal’s tensile strength and 10.3% of the fracture elongation. The fracture surface of tensile specimens showed typical plastic fracture characteristics, with no obvious crack characteristics, and no eutectic liquid films were observed.

Mechanical and microstructural characterization of AISI SAE 4130 steel welded joints made by robotic gas metal arc welding process: influence of electrode work angle in 'T' welded joints

“…The rapid GMAW joint exhibited higher hardness and tensile strength in the weld metal region but lower impact toughness than the base metal. Zhao et al [10] scrutinized the mechanical properties and microstructure of Invar alloy welded by automatic GTAW. The rupture surface of tensile samples displayed typical plastic fracture features without apparent crack characteristics, and no eutectic liquid films were observed.…”