Masanori Yasuyama

Spot welding of aluminium and steel sheet with an insert of aluminium clad steel sheet: Dissimilar metal joining of aluminium and steel sheet (1st Report)

Summary This paper describes an investigation of the dissimilar metal spot welding of aluminium and steel sheet with an aluminium clad steel sheet insert. The study relates to application of this system in automotive fabrication in an effort to reduce motor vehicle weight. To ascertain the mechanical properties of the intermetallic compounds formed at the steel and aluminium bond interface, measurements were performed using four types of Fe‐Al binary system intermetallic compound. The mechanical properties of spot‐welded joints in aluminium and steel sheet with and without insertion of an aluminium clad steel sheet were measured by the cross tension test, and the microstructures of the welded joints then formed were observed. The intermetallic compounds FeAl and Fe3Al have a relatively high ductility, and Fe2Al5 and FeAl3 have a high hardness and low ductility. Fe2Al5 intermetallic compounds were formed in the spot‐welded zones of the aluminium and steel sheet, resulting in loss of strength. The dissimila...

Tailored blank technology of high strength steel sheet

Optimization of component structures, reduction in the number of components and improved yield of steel sheet are sought for tailored blank (hereafter referred to as TWB) technology, in which a welded blank material is subjected to press forming by the optimum arrangement of multiple steel sheet and one-piece forming. This technology has been employed by various automobile manufacturing companies. The demand for both safety improvements as well as for light weight automobiles has been increasing year after year and there is a developing requirement in the application of effective high tensile strength steel sheet year by year. Also, the move to high tensile strength TWB components has been taken into consideration; for example, high tensile strength steel of more than 500 MPa is employed for structural components, such as pillars and rails. TWB technology consists of the welding process and the subsequent press process of blank materials, as indicated in figure 1. Needless to say, a quality such that no cracks occur during press forming is required for welded blank materials. However, the strain direction and value near the weld line are varied since a combination of components of dissimilar strength and dissimilar sheet thickness are welded and press formed. Accordingly, when considering press forming cracking of actual components, it is necessary to consider not only the maintenance of quality of the welded blank material and the characteristics of the base metal and weld zone but also the blank configuration/component/ metal mould design etc., for which the arrangement of the weld line is taken into account. The purpose of this paper is to deepen the understanding of TWB welding technology of high tensile strength steel sheet. The laser, mash seam and plasma welding processes, which are employed for TWB were reviewed and the characteristics of the welding processes and case studies of the weld zone formability of high tensile strength steel using these welding processes are introduced in this paper.