Optimizing tensile strength of low-alloy steel joints in upset welding

Purpose: Purpose In resistance upset welding, the heat is generated by resistance of the interface of abutting surfaces to the flow of electrical current in heating and post-weld heating stages. Upset welding typically results in solid-state welds with no melting at the joint. In this paper, the effect of process parameters including heating and post-weld heating power and their corresponding duration along with interference, on the tensile strength of the welded joint are experimentally investigated. Design/methodology/approach: The operational ranges of five process parameters are identified. Sufficient numbers of samples are manufactured and subsequently their mechanical strength is quantified using tensile tests. Then variation of the strength versus the process parameter is evaluated. Metallographic studies are performed that provide metallurgical insight to the bond. Findings: The results suggest that tensile strength of the joint, with variation of each investigated parameter, time, current, and electrical power has an optimal point which shows the optimized set of welding parameters. Also the effect of post-weld heating on the tensile strength is evaluated and shows that this parameter has a remarkable effect exceeding 50% improvement in tensile strength. Research limitations/implications: Should the percentage of power consumption replaced by current; a better comprehension of the process could be achieved. Practical implications: The results recommend that the effect of post-weld hating merits more investigation. Originality/value: The results contribute to a better understanding of the upset welding process. More over this paper shows significance of post-weld heating in maximum tensile strength of the weldment that has not been noted as an important upset welding process in other literature.