The influence of laser beam welding and plasma arc welding processes on dual phase steel microstructure

One important aspect in the application of dual phase (DP) steels in the automotive industry are their weldability and subsequent mechanical properties. Welding involves a rapid change in the temperature which alters the microstructure and the mechanical properties of the steel. Understanding the influence of welding conditions on the mechanical properties of DP 600 is useful both the automotive industry and steel producers. Despite its importance, the weldability study of dual phase steels is still limited. In this paper the microstructural evolution and its influence on the mechanical properties of 1 mm thick zinc coated DP 600 steel are described for laser beam welding (LBW) and plasma are welding (PAW) processes. Microstructural and mechanical characterisation were performed using optical microscopy, microhardness measurements, tensile tests and Erichsen cupping tests. The process comparison shows differences in the final mechanical properties resulting from the microstructural differences in the welding zones.