Preventing nugget shifting in joining of dissimilar steels via resistance element welding: a numerical simulation

Abstract

Joining the advanced high strength steels and the conventional steels is a critical issue for the manufacturing of lightweight vehicles. Resistance element welding (REW) is an emerging joining method for dissimilar metals and alloys by applying an auxiliary rivetlike resistance element in resistance spot welding (RSW). In this study, an electricalthermal-mechanical coupled REW model for high-strength dual-phase (DP) steel and Q235 steel was developed by considering contact resistances as functions of temperature and surface contacting area. The results show that the welding element in REW serves to concentrate the current flow and thus Joule heat generation at the faying interface between the element and workpiece. For welding DP600 and Q235 workpieces with a small thickness ratio (≤0.4) or a high electrical resistivity ratio (≥3), REW could effectively mitigate nugget shifting between workpieces and reducing the thermal excursion to electrode as compared to RSW. Adding well-designed insulation layers in REW could further concentrate the current within the welding element, and enables a large-sized nugget at a lower current. This study is significant because it provides a better understanding to the electrical-thermal-mechanical behaviors with interfacial contacts in REW and contributes to its further advance.

Microstructure and Mechanical Properties of Resistance Element Welded Joints for DP780 Steel and 6061 Aluminum Alloy

“…In general, the highest temperature of the joint obtained by RSW is distributed at the workpiece interface, and the closer the location to the workpiece interface, the higher the temperature. [ 32 ] The temperature distribution of REW was similar to that of RSW. Consequently, the temperature distribution at the Q235 steel/Al interface bottom was higher than that at other locations, and the thickness of the IMC layer at the Q235 steel/Al interface bottom was thicker than it was at other locations.…”

“…REW is a novel joining technology for all dissimilar materials based on thermal-mechanical joining principles. [28][29][30][31][32] It can effectively avoid IMC formation at the welding interface. Furthermore, it can convert dissimilar materials joining into similar materials to improve the mechanical properties of the joint.…”

An Overview of Resistance Element Welding with Focus on Mechanical and Microstructure Joint and Optimization in Automotive Metal Joints

“…Recently, a 3D numerical model for high-strength Dual-Phase(DP) 600 steel and Q235 steel by considering contact resistances as functions of temperature and surface contacting area was developed 52) . The electric current flow and thus Joule heat generation at the faying interface between the element and workpiece as the welding parameters in REW were observed.…”