Abstract
KEYWORDS – Automotive, Brazing, High-strength Steel, Multi-Material-Design, Lightweight Design
ABSTRACT
Arc brazing of high-strength steel and steel-aluminum dissimilar materials offers a great opportunity to the automotive industry.
It is, on the one hand, possible to join steel-aluminum dissimilar materials. The main problem is the development of the inevitable intermetallic layers. One objective of this study is to reduce the negative impact of these intermetallic layers on the strength properties. On the other hand, high-strength steels can be joined by using copper-based brazing materials. However, there is a lack of comprehension regarding the specific input parameters and the interaction between the joining parameters, the seam geometry, the filler material, the process stability, the reproducibility and the component behavior. This study serves the purpose to fill this knowledge gap, mainly with regard to the seam geometry and the strength properties. By using zinc-based brazing materials and modern digitally controlled short arc processes it is possible to successfully conduct low-energy joining of steel aluminum dissimilar metals. The same process in combination with a copper-based brazing material is suitable for high-strength steel joints. For both brazing materials, a large number of joining tests have been conducted to reach a high degree of comprehension concerning the impact of the various joining parameters on the joining results. To validate the results of the joining tests, metallurgical analyses and SEM and EDX analyses were carried out. In addition, tensile strength and cyclic tests were accomplished.
For the tensile tests of the brazed high-strength steel lap joints, a digital image correlation system was also used.
In this paper, the correlation between the intermetallic layers and the tensile strength of steel joints using copper-based brazing wires is presented. Continuing, the publication shows that it is possible to reduce the negative impact of the intermetallic layers and to make the short arc process suitable for the joining of steel aluminum dissimilar materials in vehicle production in combination with zinc-based brazing materials.