Evaluation of the mechanical properties of high nitrogen-containing austenitic stainless steel friction stir welds

摘要

The friction stir welding of 2 mm thick high nitrogen-containing austenitic stainless steels plates was successfully performed using a load-controlled FSW machine with a Si_3N_4-based tool. To determine the optimum conditions to create reliable HNS FSW joints, the effect of heat input on joint properties depending on some welding parameters, i.e., the tool rotation speed, welding speed were examined. Four welding conditions, different welding speed i.e., 400, 200, 100, 50 (mm/min) and a constant tool rotation 400rpm were examined in this study. In all conditions, full-penetrated and defect-free butt welding joints were successfully produced. The stir zone showed a Vickers hardness higher than the base metal and showed a fine microstructure due to recrystallization. The yield strength and the tensile strength of the welds produced by the Si_3N_4 tool exceeded that of the base metal. The present study shows that FSW is one of the efficient joining processes that can produce sound HNS weld joints.