Mechanical properties of high strength S690 steel welded sections through tensile tests on heat-treated coupons. (March 2020)

• Record Type: Journal Article
• Authors: Ho, Ho-Cheung; Chung, Kwok-Fai; Huang, Ming-Xin; Nethercot, David A.; Liu, Xiao; Jin, Hao; Wang, Guo-Dong; Tian, Zhi-Hong
• Is Part Of: Journal of constructional steel research. Volume 166(2020)
• Publication Date: 2020-03
• Subjects: High strength steels -- Welding -- Mechanical properties -- Change in microstructures -- Thermal mechanical simulation -- Strength and ductility; Steel, Structural -- Periodicals; Building, Iron and steel -- Periodicals; Acier de construction -- Périodiques; Construction métallique -- Périodiques; 624.1821
• DOI: 10.1016/j.jcsr.2019.105922
• Languages: English
• ISSNs: 0143-974X

Abstract

Abstract: 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. Highlights: Based on practical welding processes, various heat input energy were specified to establish parameters of temperature histories, i.e. maximium temperatures and cooling rates t8/5, for subsequent correlation with changes in microstructures. Gleeble ®2000 Thermal Simulation Testing Machine is adopted for thermal-mechanical physical simulation to produce various types of microstructures within Heat-Affected-Zones (HAZ) of S690 steels. Stress-strain characteristics of various types of microstructures under different cooling rates are obtained through standard tensile tests, and corresponding reduction factors for their mechanical properties are determined. Images of various types of microstructures are obtained with the use of Scanning Electron Microscope (SEM), and hence, the volumetric fractions of various target phases of the heat-treated S690 steel coupons are estimated. Correlation between microstructures and mechanical properties of the S690 welded sections is established.