通过拉伸试验测定了X70大变形管线钢管的屈服强度Rt0.5、抗拉强度Rm、屈强比Rt0.5/Rm、应力比、均匀变形伸长率, 并对比了系列温度下的冲击韧性, 分析了管体的显微组织以及-100 ℃冲击断口的形貌。结果表明: 管体纵向具有优异的拉伸性能, 最小的Rt0.5为478 MPa, Rt0.5/Rm低于0.69, 均匀变形伸长率大于11%;-100 ℃时的横向冲击吸收能为120 J, 剪切断面率为90%;断口呈韧性断裂特征, 管材具有良好的低温韧性, 韧脆转变温度低于-100 ℃;该管线钢是以铁素体、粒状贝氏体为主的双相组织, 管体中心存在显著的粒状贝氏体带。

The yield strength, tensile strength, yield ratio, stress ratio, uniform elongation of X70 high deformability linepipe were tested by tensile experiment. The impact toughnesses at different temperature were compared.The microstructure and impact fracture morphology of the line pipe at -100 ℃ were analysed. The results show that the linepipe had excellent longitudinal tensile properties, the lowest value of Rt0.5 was 478 MPa, Rt0.5/Rm was lower than 0.69 and the uniform elongation was higher than 11%. The transverse absorption energy of the linepipe at -100 ℃ was 120 J and the shear section rate was 90%, the ductile fracture showing that the steel had good toughness properties at low temperature and the ductile-brittle transition temperature was lower than 100 ℃. The main microstructure of the linepipe were ferrite and granular bainite. The granular bainite band significantly existed in the center of the line pipe.