Understanding the bonding mechanism in short-time resistance projection welding: a comprehensive analysis

Abstract

AbstractCapacitor discharge welding (CDW) is characterized by a pulsed electrical current profile. It is primarily utilized for resistance projection welding tasks, offering high power densities and short welding times. According to the latest findings, the welding process can be divided into different phases: contacting, activating, material connection, and holding pressure. During the activation phase, high-speed video-imaging reveals the generation of metal vapor which effectively eliminates impurities and oxide layers from the contact zone. The result of this is an activated surface. The purpose of this paper is to describe the physical effects of the bonding mechanism during short-time resistance welding. The Chair of Joining Technology and Assembly at the Technische Universität Dresden has a laboratory facility that can interrupt the welding current at any desired time during capacitor discharge welding. This allows different welding current profiles with always the same current rise time to be scientifically investigated. The experimental findings were supplemented with simulative analyses to clarify the bonding mechanism in resistance projection welding. Three different surface conditions are considered to generalize the findings on the bonding mechanism. Temperature and current density distributions were assessed to provide a physical description of the activation phase. The power density in the joining zone at different interruption times is determined, which gives an indication of activation by metal vaporization. The material connection is determined experimentally for the same interruption times. The numerical simulation model can be used to describe the bonding mechanism in short-time resistance welding. In resistance welding, the bond is formed due to the molten phase (solidification structure). In short-time resistance welding, the bond is formed due to surface activation by metal vaporization.