TWI

In relation to the European funded research project HILDA (high integrity low distortion assembly) to encourage the industrial take up of friction stir welding (FSW) for structural steels, an investigation was undertaken into the microstructure and mechanical properties of butt joints fabricated by FSW in DH36 microalloyed shipbuilding steel (0.11%C, 1.48%Mn, 0.02%Nb, 0.02%Al) plates (thickness 6 mm). The process parameters varied were tool traverse speed (100-500 mm/min) and rotational speed (200-700 rpm). The microstructures of parent metal and thermomechanically affected zone (TMAZ) were observed by optical microscopy. Mechanical properties were characterised by microhardness measurements, transverse tensile, V-notch Charpy impact and fatigue testing, and fracture surface observations. Issues discussed include microstructure grain refinement, the influence of traverse speed on yield strength and the relationship between weld flaws and fatigue performance.

11th International Symposium, 17-19 May 2016, Session 8A: High Temperature II, Paper 04