Recently, high nitrogen steels containing more than 1 wt% nitrogen, resulting in both high mechanical properties and good corrosion resistance, have been developed. However, they exhibit very poor fusion-weldability because they experience desorption of nitrogen and porosity formation during fusion welding processes. On the other hand, FSW (friction stir welding) would be an effective welding method to alleviate problems associated with fusion welding processes in HNSs (high nitrogen steels) because it is a solid-state joining process. The objective of this study was to clarify the effect of welding parameters on the properties of friction stir welded steel containing 1.3% nitrogen. FSW produced defect-free welds in high nitrogen steel at various welding parameters. FSW refined the grain structure in the stir zone, which resulted in higher hardness, strength and toughness than the base material. Simultaneously, FSW resulted in rapid precipitation of chromium nitrides on the grain boundaries in the stir zone, which caused reduction of the corrosion resistance. This study showed that FSW was an effective method to produce a defect-free weld in the HNS and that a combination of high rotational speed and high travel speed resulted in better mechanical and corrosion properties of the stir zone.
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