ABSTRACT

In the North Sea oil and gas installations, steel castings have been used for many decades. Here, high strength steel castings offer the chance to manufacture complex heavy-lift and fatigue-critical components for larger offshore structures without increasing the weight of the components or platforms. However, when the activities are moving north to colder climates, current existing castings may fail to meet the toughness requirements, and there is very limited information available on behaviour of weldments of castings under such extreme conditions. Therefore, the present investigation was carried out addressing the low temperature toughness of high nickel (~1.5% Ni) steel casting with 460 MPa yield strength. Preliminary welding trials were performed with flux-cored arc welding (FCAW) with an overmatch in weld metal strength. Both Charpy V notch impact and CTOD fracture mechanical testing were included at ?60°C. The results show that the Charpy V notch toughness is excellent at -60°C (> 100 J). The fusion line CTOD fracture toughness showed low values for the SENB05 samples, while SENB02 gave higher values. For both geometries, the lowest values were connected with pop-in events. The weld metal fracture toughness was satisfactory with the lowest value of 0.28 mm.

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