Study of microstructure and mechanical properties of high thickness A844/A516 steel joints by multi-pass GMAW for pressure vessels.

In this study, the gas metal arc welding (GMAW) process was investigated for similar and dissimilar joints of A844 and A516 steel plates in different thicknesses. For welding, E 19-10H filler metal and category D joint design were used for joining nozzles to the cargo tank body. Also, the dependence of the microstructure, strength, and impact energy (cryogenic fracture toughness) on the cooling rate (∂T/∂t) was evaluated. Due to the effect of the square of thickness on the heat transfer rate, with the increase in thickness (8–10 mm), the cooling rate (∂T/∂t) increased by 57% for similar joints. According to this increase, the strength and cryogenic fracture toughness for the similar joints of A844 steel plates increased by 8 and 9%, respectively. For similar joints of A516 steel plates, it increased by 6 and 9%, respectively. The strength and cryogenic fracture toughness of dissimilar joints with different thicknesses depended on the type of base metals and the different cooling rates of each base metal. Continuous plastic deformation was observed in the weld zone during bending tests because E19-10H filler metal has more than 30% elongation. Also, the presence of any kind of cracks in the joints was ruled out by performing radiographic tests. [ABSTRACT FROM AUTHOR]