Control of Post-Weld Fracture Toughness in Friction Stir Processed X-80 HSLA Steel

• Main Author: Crook, Nolan Tracy
• Format: Others
• Published: BYU ScholarsArchive 2021
• Subjects: API X80; friction stir welding; CTOD; fracture toughness; heat input; cooling rate; Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/9162; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=10171&context=etd

The present study investigates the fracture toughness of FSW X-80 HSLA steel welds. Weld cooling rate and peak temperature were varied among welds; indirectly manipulated through FSW travel speed, rpm, and weld preheat. Fracture toughness was tested according to ASTM 1820 standard along the weld centerline using surface-notched SEB specimen cooled to -40 °C. This study resulted in a reliable, repeatable process for generating friction stir welds with CTOD’s consistently above that of the original base metal. CTOD and microstructure of friction stir welds can be selected by controlling weld cooling rate and peak temperature. Material properties and microstructure similar to the original base metal can be recreated throughout the weld stir zone. CTOD of FSW X80 has a strong inverse linear correlation with post-weld cooling rate.