Process tape를 이용한 고강도강 3 겹 저항 스폿용접에 관한 연구

Abstract

Recently, in order to meet environmental issues and more stringent emission standards, advanced high strength steel is used to reduce car body weight. Three-sheet resistance spot welding technology for advanced high strength steel has been a challenge compared to conventional two-sheet resistance spot welding. As a new solution, the method of changing resistance is being researched. In this study, a process tape was used to solve the problem which is existed in three-sheet resistance spot welding. Tensile shear test and cross tensile test were conducted and suitable welding range was induced according to welding conditions. Also, in order to investigate the related reasons, nugget formation, cross sectional image of welds and welding signals were analyzed. Combined with Lobe diagrams, weld nugget macrostructure image and dynamic resistance from the result of welding power curve and heat input calculation, it could be found that the resistance between upper electrode and workpiece became larger and the heat input also became larger by using process tape. As a result, the formation of weld nugget between SGACEN and DP980 was easily induced, and wider suitable welding ranges, larger tensile shear strength were obtained, and meanwhile the occurrence of expulsion was also prevented, thereby improve the weldability of three-sheet RSW.