Seam Welding and Cooling-Control Heat-Treatment of Martensitic Stainless Steel

Abstract

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 timeconsuming 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.