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利用热模拟、力学性能测试和材料显微分析等实验技术,研究了X80管线钢在延迟加速冷却条件下的组织与性能的变化。结果表明,通过延迟加速冷却,X80管线钢可获得贝氏体+铁素体(B+F)双相组织。随着始冷温度的上升,试验钢的B含量增加,F含量降低,导致材料屈服强度上升,塑性下降。当始冷温度为530℃时,X80管线钢有较低的屈强比,较大的均匀伸长率和较大的形变强化指数,符合大变形管线钢的技术要求。通过延迟加速冷却方法获得的细小的B板条和较高位错密度的F赋予材料较高的强韧特性和优良的大变形能力。
The microstructure and mechanical properties of X80 pipeline steel under delayed accelerated cooling conditions were studied by means of thermal simulation, mechanical property test and material microscopic analysis. The results show that bainite + ferrite (B + F) dual phase structure can be obtained in X80 pipeline steel by delayed accelerated cooling. With the increase of initial cooling temperature, the content of B in test steel increases and the content of F decreases, which leads to the increase of yield strength and the decrease of ductility. When the incipient temperature is 530 ℃, X80 pipeline steel has a lower yield ratio, a larger uniform elongation and a larger deformation enhanced index, in line with the technical requirements of large deformation of pipeline steel. The small B lamellae and the higher dislocation density F obtained by the delayed accelerated cooling method give the material higher toughness characteristics and excellent large deformability.