Friction stir welding of thick section reduced activation ferritic–martensitic steel

Abstract

Full penetration friction stir welding was conducted on 12 mm thick reduced activation ferritic-martensitic steel at tool rotational speeds of 500 and 900 rev min −1 . Comparator welds at 500 rev min −1 were also produced in 6 mm thick reduced activation ferritic-martensitic steel plate to evaluate section thickness effects. Increase in section thickness led to an increase in heat input, which strongly influenced the microstructure evolution in stir zone (SZ), thermomechanical affected zone and the overall hardness in the SZ of this steel. In the as-welded condition, the base metal microstructure was significantly altered and resulted in carbide-free grain boundaries. The desirable microstructure and mechanical properties were achieved by subjecting the as-welded joints to appropriate post-weld heat treatments.

Effect of friction stir and activated-GTA welding processes on the 9Cr–1Mo steel to 316LN stainless steel dissimilar weld joints

“…The density distribution of low angle grain boundary (LAGB) and high angle grain boundary (HAGB) of 316LN BM was ∼ 9.7% and ∼ 90.3%, respectively, whereas the SZ matrix contains 47.3% of LAGB and 52.7% of HAGB. The severe plastic deformation associated with FSW induces the dislocation, and owing to the recovery effect, it gets rearranged in the form of low energy cells or subgrains [17]. Therefore, the density fraction of LAGBs in the SZ is comparatively higher than that of 316LN BM.…”

Formation of delta-ferrite and its effect on impact toughness of GTAW weld metals in a 12 wt-% Cr steel

“…High-chromium (9-12 wt-% Cr) ferrite/martensitic (F/M) heat-resistant steels have been considered as primary candidate materials for core components of the Generation IV reactors mainly due to their superior dimensional stability and adequate compatibility with the coolants [1,2]. Currently, the assembly of the cladding tube and duct in the core structure requires the use of fusion welding process, like argon tungsten arc welding (GTAW).…”