CONSTR UCTION & FABRICATION
Steel that Beats Conventional Grades OFFSHORE FACILITIES ARE EXPOSED TO HIGH STATIC AND DYNAMIC LOADS GENERATED BY WATER, WIND, WAVES AND LOW TEMPERATURES. IN SOME LOCATIONS, SUCH STRUCTURES ARE required to reliably withstand waves of over 25m in height and gale-force winds gusting at up to 160km per hour or more. In the North Sea, or even further north in particular, temperatures can reach -10°C or below, demanding dependable material toughness properties at test temperatures of -40°C or even lower.
B
ecause of these severe circumstances, requirements made on the grades of steel used for the construction of monopiles for offshore windfarms are high. Only absolutely excellent mechanical properties appropriate to the application, consisting of yield strength, tensile strength and toughness, can give such structures the necessary stability and safety. In addition, the availability of large plate formats, with excellent dimensional and flatness tolerances and weldability properties, are definitive preconditions for costefficient production. The offshore industry uses two differing groups of standards, which are selected on the basis of construction conditions. The differentiation criterion is, above all, the precise origin of the Charpy V-notch impact test specimen, which is taken either at one quarter (the EN 10025, series of standards on hot-rolled structural steels for offshore use) or at half plate thickness (the classical EN 10225 series, dealing with ‘Weldable structural steels for fixed offshore structures’). The origin of the samples from zones of differing solidification morphologies makes it possible to achieve differing maximum thicknesses, depending on the group of standards.
Thermo-Mechanically Rolled Plates
Dillinger, one of Europe’s leading producers of heavy plates, meets these offshore industry requirements with thermo-
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