Mechanical properties of high strength S690 steel welded sections through tensile tests on heat-treated coupons

High strength S690 steels achieve their greater strength through heat treatment, the benefits of which may be to some extent reversed if the steels are subsequently welded. In order to investigate this, a systematic experimental investigation into the mechanical properties of small coupons of the S690 steels representing 3 regions within the heat affected zone (HAZ) of the welded joints produced using temperature-time histories derived from different practical welding procedures was carried out. By employing specially designed funnel-shaped coupons, it was possible to generate highly consistent microstructures for the different phases of the recrystallized S690 steels that are representative of those produced by welding. These microstructures were identified using scanning electron microscopes to demonstrate an evolution of microstructure within the HAZ of the welded sections. Using the stress-strain curves from monotonic tensile tests on these coupons, it has been possible to correlate key features of various deformation characteristics in the different regions with their corresponding microstructures. The findings show that the potentially deleterious effects of welding on the mechanical properties of S690 steel may be substantially reduced through careful control of the welding process.