Experimental Study on Mechanical Properties of Fillet Weld Connections of S30408 Stainless Steel in Low Temperature

As an essential part of a pressure vessel, the mechanical properties of welded joints at low temperatures directly influence the vessel's safety. At present, most research on mechanical properties of stainless steel welded joints focuses on butt weld at the experimental temperature range between room temperature and -196℃. However, fillet weld at different temperatures has been scarcely investigated. To study the low-temperature mechanical properties of the S30408 stainless steel fillet weld joint, the low-temperature tensile tests were performed on 15 transverse and longitudinal fillet weld joint specimens in the temperature range -60-20℃ using a 100t universal testing machine. Besides, the stress-strain curves, weld strength, deformation, and failure characteristics were measured. The fracture morphology was observed using a thermal field-emission scanning electron microscope, and microstructure characteristics were analyzed. The results show that -60℃ compared to 20℃, the yield and tensile strength of the transverse fillet weld increased by 18% and 25%, respectively, and that of the longitudinal fillet weld increased by 35% and 30%, respectively. Low temperature hardening effect is remarkable. The ratio of the tensile strength of the transverse fillet weld member to the longitudinal member is slightly less than the theoretical value of 1.5. The results show that the combined action of tensile and shear forces influence the transverse fillet weld. The elastic modulus of the transverse fillet weld is 198 GPa at 20℃ and the longitudinal member is 102GPa under the action of shear force. The elastic modulus increases gradually with decreasing temperature. The elastic modulus of the transverse member increases by a maximum of 6% and the longitudinal member by 9%. The fracture surface of the front fillet weld has polygonal dimple morphology, and the longitudinal one has shear dimple morphology. The number of dimples decreases with the decreasing temperature, the color lightens, and the plastic deformation ability weakens; however, the fracture is still ductile. © 2022, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.