Recent linepipe steel is required to have enough deformation capacity through longitudinal direction at severe environments such as permafrost or seismic region, even though after anti-corrosion coating treatment in pipe. Under this background, the development of X100 linepipe steels with high strain aging resistance was tried. As a basic study, the effects of aging temperature, pre-strain and specimen dimension on the strain aging of pipes were carefully studied. It was found that strain aging behavior of plate and pipe was different in through thickness direction and specimen position along circumference. Several experimental trials with lots of process variables have been performed to enhance the strain aging resistance of X100 linepipe steels. By changing chemical composition and rolling / cooling condition, X100 plate steel was newly produced for achieving the high deformation capacity. X100 pipes with 1m length were manufactured by using UOE simulator which can do U-ing, O-ing and expansion at the same machine. After pipe forming, coating simulation to evaluate strain aging characteristics of pipes was performed by with small specimen. The yielding behaviors were examined after aging treatment for coating simulation.

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