Application of FSW to high carbon and high phosphorus weathering steel
By Takumi Kawakubo (Joining and Welding Research Institute Osaka University), Tomoya Nagira (Joining and Welding Research Institute Osaka University), Kohsaku Ushioda (Joining and Welding Research Institute Osaka University), Hidetoshi Fujii (Joining and Welding Research Institute Osaka University)

Weathering steel has attracted attention in terms of the life-cycle cost of bridges since it shows excellent corrosion resistance due to the formation of a protective rust layer on the surface. In weathering steels, the additions of C and P are expected to simultaneously increase the strength and corrosion resistance. However, solidification cracking easily occurs in fusion welding. Therefore the amount of additional alloying elements is currently limited. On the other hand, friction stir welding (FSW), which is a solid-state joining process, can overcome the problems of weldability in the fusion welding. In this study, high C and high P steels were investigated together with the existing weathering steel (COR-TEN490). FSW was performed under high and low heat input welding conditions, and the weldability of the FSW joint was examined. In addition, the microstructure and mechanical properties such as strength, toughness and ductility of the joint were investigated.