Friction Stir Welding of High Phosphorus Weathering Steel —Weldabilities, Microstructural Evolution and Mechanical Properties

Phosphorus (P) addition is expected to simultaneously increase the strength and corrosion resistance of weathering steels. However, P causes solidification cracking in fusion welding process reduces toughness steel. To avoid these problems, content weldable SMA490AW steel currently limited below 0.035 mass%. High steels which are impossible be joined by process, can a solid-state joining i.e., friction stir (FSW). Because zone obtained FSW contained very fine grains, its was improve. This study applies high-P examines weldability product. The microstructural evolution mechanical properties were investigated at different temperatures. macroscopic cross-sectional observations joints revealed crack-free structures even containing 0.3 mass% P. Moreover, significantly refined grain structure zone. Consequently, ductile-to-brittle transition temperature approximately 150°C lower welded A1 (average size = 2.5 µm) than base material 23 µm). It appears that refinement overcomes embrittlement caused excessive content.