A Study on the Dissimilar Metal Joining of Aluminum to Steel Using the Arc Heat Source (Ⅲ) - Static Strength and Fracture Behaviors -

Abstract

In order to commercialize the steel to aluminum joining technology using arc heat source in the automobile industry, it is the most important to secure a reliable joining strength. However, there is not enough to describe the overall static strength characteristics of dissimilar metal joints. Therefore, in this study, the tensile-shear test was performed according to the process parameters which affect the strength of the lap joint structure. As a result, the porosity of the Al-Fe dissimilar joint has a greater influence on the strength due to the vaporization of Zn present in the root zone than the geometrical shape of the bonded length or the wetting angle. In addition, it was confirmed that the crack was initiated due to the root pore, along with cracks in the vicinity of the continuous pore by fractography analysis. Decrease of the tensile strength is due to the reduction of the absolute cross-sectional area result from the pores present in the weld metal. Finally, from the results of stress analysis using FEM, it was confirmed that the pore of the root zone due to the increase of the heat input had a greater influence on the strength even though the interface bonding length was increased.

Joint Properties of Aluminum Alloy and Galvanized Steel by AC Pulse MIG Braze Welding

“…Especially, the root area, where the Al alloy and steel sheets were tightly joined, had a high thermal conductivity, resulting in the faster solidification, causing sufficient heat input to not transfer properly. Therefore, pores and the lack of fusion were easily formed in the root area [15,16].…”