The Possibility of Friction Stir Welding of High Nitrogen-containing Austenitic Stainless Steel

概要

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To develop the practical use of high nitrogen-containing austenitic stainless steels (HNS), the possibility of using friction stir welding (FSW) of HNS was examined. In this report, butt-welding of 2 mm thick HNS steel plates was performed using a load-controlled FSW machine. Two types of welding tool materials were used in this study, namely, a Si3N4-based material and a WC-Co-based material. For FSW with Si3N4, full-penetrated and defect-free butt welding joints were successfully produced. On the other hand, for FSW with WC-Co, the tool was deformed and the stir zone did not completely reach the bottom. The stir zone produced by the Si3N4 tool showed a Vicker's hardness higher than the base metal and displayed a fine microstructure due to recrystallization. The yield strength and the tensile strength of the welds produced by the Si3N4 tool exceeded that of the base metal.