Effects of different welding technologies on metallurgical and mechanical properties of DP600 steel welded joints.

Considering the safety standards required in the automotive industry, dual phase (DP) steels have gained their popularity thanks to their higher tensile strength in conjunction with superior formability if compared to the steel grades of similar yield strength. Such properties are related to their microstructure which consists of soft and ductile ferrite matrix, strengthened by hard martensitic phase. It is well known that welding processes play an important role in the automotive industry. While the conventional arc-welding processes are well-established, flexible and easy to automate, high power density processes guarantee low distortions, narrow fusion and heat affected zones. The performance evaluation of welded automotive components made in DP steels, with respect to durability or crashworthiness, involves the quantification of the properties change of the welded joint. This work is aimed at evaluating the effects of three different welding technologies (GTAW, PAW, EBW) on dual phase DP 600 steel properties. In particular, the soundness, the fusion and heat-affected zone microstructure, and the mechanical properties of the welded joints are analyzed and compared in detail.