Abstract
An investigation has been made to develop a simple duplex steel for line-pipe application. Controlled rolling of an Fe–0.06C–1.5 Mn alloy followed by direct quenching produced a duplex ferrite–bainite structure in which the coarse upper bainite regions were uniformly distributed within a fine-grained ferrite matrix. The microstructure and mechanical properties of this duplex structure were strongly influenced by the processing variables. Decreasing the finish-rolling temperature improved both tensile and impact properties. This was due mainly to a refinement of the ferrite grain size. There was an abrupt increase in the yield strength and a small increase in the ductile–brittle transition temperature as a result of cold working (pipe forming) because of the steel's continuous yielding behaviour and high initial work-hardening rate. The mechanical properties attained in this duplex steel are attractive for low-temperature line-pipe applicaiion.
MST/155
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