Microstructure and mechanical properties of X80 pipeline steels in different cooling schedules

Min ZHOU , Linxiu DU and Xianghua LIU State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819, China

摘 要：The microstructures and mechanical properties of three X80 pipeline steel plates were investigated in this study.The plates were hot rolled by two stages, and cooled by three different cooling schedules to obtain different microstructures and mechanical properties.Transmission electron microscope（TEM） was used to observe the microstructure.The results indicated that the amount of polygonal ferrite（PF） and quasi-polygonal ferrite（QPF） decreased with decreasing of the finish cooling temperature（FCT）, while the amount and size of M-A islands were larger.Relaxation promoted the Charpy V-notch（CVN） impact toughness at-20℃, but not the drop weight tear testing（DWTT） property at-15℃, and decreased the strength of the steel.

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