FRICTION STIR WELDING OF FERROUS ALLOYS: CURRENT STATUS

Friction stir welding (FSW) offers many potential benefits including reduced distortion, lower cost, no harmful airborne emissions, semi-automated, etc. Although initially developed for Al alloys, considerable work now has been completed to explore the ability of FSW to weld relatively thin (6 mm) ferrous alloys including many alloys of interest to the ship building industry such as HSLA-65. The status of current progress for ferrous alloys is presented offering insight into capabilities and opportunities as well as areas of FSW activity requiring additional improvement Practical issues of weld penetration depth, gap tolerance, post-FSW mechanical properties, and distortion are addressed. Special consideration will be made to address the ability to friction stir weld 6 mm thick HSLA-65 steel with no/low distortion. Tool materials discussed will include polycrystalline cubic boron nitride (PCBN) and a new composite tool fabricated from PCBN and W-25Re. Last, data will be presented illustrating the complete absence of harmful airborne emissions when welding an austenitic stainless steel.