Identification of additional process parameters for impact welding and their influence on the process window

Abstract

Impact welding in general facilitates the metallurgical bond even between dissimilar metals due to the lack of extensive heat input. It thus offers superior joint properties such as a good mechanical strength. However, in contrast to fusion welding, the fundamentals are not fully understood. As a direct consequence, not all influencing process parameters are known or quantified yet. However, this is crucial in order to further comprehend, develop and optimize the process. The objective of this study is to investigate the influence of the surrounding gaseous medium on the weld strength as additional parameter. This issue has been discussed in earlier publications of other researchers already, though without any consistent conclusion yet. The results of this study show that a lower gas density results in higher weld strength, whereas higher densities may even inhibit the joint completely at identical impact velocities. High speed images of the electromagnetic pulse welding process indicate that this might be caused by the jet which is obstructed by the ambient gas atmosphere on its way out of the impact area. The higher the density, the slower the visible jet is. Thus, superficial material of the workpieces and contaminants cannot leave the welding area and hinder its formation instead.