Evaluation of multipass welding of thick lean duplex stainless steel UNS S32304 plates welded by SMAW, GMAW and FCAW: part 1: Mechanical Properties

The duplex stainless steels (DSS's) have been placed as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. However, DSS's, including the lean duplex, present lower weldability than the austenitic stainless steels. Thus, this study aims to evaluate the multipass welding of 22 mm plates of lean duplex stainless steel alloy UNS S32304, using the process SMAW, GMAW and FCAW with consumables with two types of chemical composition, 22%Cr9%Ni3%Mo and 23%Cr7%Ni giving a total of six experiments. V-grooves with 60º and ceramic backing for welding the root pass were used and the heat input was maintained constant at 1.6 kJ.mm-1. It was determined the time and sequence of welding passes, aiming an analysis of productivity. The welded joints were subjected to x-ray END and specimens for tensile, bending, Charpy at -30ºC and microhardness were extracted. The productivity of the semi-automatic processes proved to be at least 63% greater than the SMAW process while the process FCAW showed 6-18% faster than the GMAW. It was found discontinuities (porosity) acceptable according to ASME B31.3 in some experiments that did not affect negatively the mechanical results, which stayed above the parent material requirement and meet fabrication standards.

Duplex; Lean Duplex; Weldability; Multipass Welding; Mechanical Properties