|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Friction Stir Welding and Processing IX
||FSW Studies to Achieve High Charpy Impact Energy in 19 mm Thick ASTM-A6 Steel
||Murray W. Mahoney, Russell Steel, Dale Fleck, Steve Larson, Trever Davis
|On-Site Speaker (Planned)
MegaStir has demonstrated the ability to FSW ASTM-A6 steel plate to a depth of 19 mm in a single pass. Weld appearance is excellent, transverse tensile strength and hardness equivalent to parent metal, and the weld nugget free of volumetric defects. However, Charpy impact results at -20°C are low. Additional weld trials were completed to understand the source of low impact energy and to provide an approach to increase Charpy impact energy values. FSW trials included a significant modification of the weld parameters to reduce heat input. Previously, weld nugget microstructures were predominantly a Widmanstätten structure and a mixture of phases. Conversely, with much lower heat input, the microstructure appears to be almost entirely proeutectoid ferrite. Very high Charpy impact energy values at -20°C were demonstrated in both ASTM-A6 steel plate (94 ft-lbf) and X-60 pipe (211 ft-lbf). These impact values are well above the program goal of 45 ft-lbf.
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