TWI

With regard to the development of 9%Ni steels for cryogenic applications, an investigation was undertaken into the metallurgical weldability of ASTM A553 Type I steel (0.08%C, 0.73%Mn, 9.4%Ni) joined by double-sided two-run friction stir welding (FSW), the influence of the second run in the stirred material from the first run, and the microstructure and mechanical properties of the welded joints. FSW was carried out using a polycrystalline cubic BN tool with scrolled shoulder and probe at a rotational speed of 400 rpm, travel speed of 60 mm/min and welding force of 25 kN. Stir zone microstructure and phase composition were observed by optical microscopy, electron backscatter diffraction mapping and X-ray diffraction. Mechanical properties were characterised by Vickers microhardness measurements and Charpy V notch tests at -196 deg.C. The energy from the Charpy impact tests was correlated with grain size, volume fraction of retained austenite and volumetric fraction of martensite-austenite constituent by multiple linear regression.

12th International Symposium, 26-28 Jun 2018, Session 7B: High Temperature II, Paper 02