Dissimilar Laser Welding of Titanium and Steel Using Chrome Insert Metal

Dissimilar welding of thin plates of conventional pure titanium and steel was investigated using an insert metal of the chromium plate to avoid the formation of brittle intermetallic compounds consisting of Ti and Fe. The Cr atom also can form intermetallic compounds with Ti atom though the formability is less than that of Ti/Fe. Therefore, the effect of dilution of Cr on the forming of intermetallic compounds in the weld metal by laser welding process, which has larger cooling rate comparing to the conventional arc welding, was evaluated. The weld metals with various level of dilution by Cr were obtained by adjusting the offset of laser beam irradiation from the interface of titanium and chromium plates. As the result it was found that the formation of intermetallic compound was prevented in the condition of the dilution lower than about 40 %. However, the excess offset to reduce the dilution of chromium plate can cause weld defects such as the lack of fusion. That problem was solved by achieving low dilution with the addition of titanium wire in the laser welding process without offset. In conclusion, it was confirmed the sound dissimilar welded joints resulting in sufficient mechanical properties were obtained by applying the proper welding condition based on the findings in this work.