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Martensitic stainless steels are ideally suited for structural components and assemblies, satisfying the requirements of high strength, toughness and corrosion resistance with ease of forming in the annealed state. New developments in welding and thermal processing, coupled with increased demands for high strength lightweight structures, are positioning martensitic stainless as a cost effective alternative to conventional lightweighting materials. Several examples are shown, including the development of fully martensitic (UNS S41000) automotive subframes, door beams, B-pillars, seat rails, tow hooks and fuel rail assemblies. The excellent mechanical properties of hardened martensitic stainless allow for notable weight savings, achieving 35% or greater weight reduction relative to baseline designs.

From a production standpoint, many high-strength welded (GTAW, GMAW, laser, etc.) assemblies require post-weld mechanical forming operations. Complications often arise when using Advanced High Strength Steels (AHSS), whose chemical composition may lend it to fully martensitic, extremely brittle as-welded microstructures. Martensitic Stainless Steels (MSS) are a particular class of AHSS susceptible to high fusion and heat-affected zone (HAZ) hardness after welding. The focus of this study is to provide a relatively straightforward way to improve the ductility of as-welded air-hardenable martensitic stainless steel joints without subjecting the weld to a separate costly and time-consuming off-line pre-or-post weld heat treatment. The additional ductility afforded by such a method can greatly expand the design opportunities using commercially available martensitic stainless alloys, which are capable of strengths in excess of 1400 MPa after a final solution heat treatment.