【摘要】 利用光学显微镜、扫描电镜、显微硬度计、万能电子拉伸试验机等，研究了深冷处理、调质以及调质+深冷处理对X70管线钢显微组织及力学性能的影响。结果表明，未经处理X70管线钢组织为铁素体+珠光体；仅深冷处理后组织更加细小、均匀且珠光体含量减少，显微硬度提高了2.73%,抗拉强度提升9.58%,拉伸断口形貌为等轴韧窝，为韧性断裂特征；调质处理后X70管线钢组织为铁素体+回火索氏体+贝氏体，相较未处理试样，硬度提高了13.62%,抗拉强度提升5.64%,拉伸断口分布有韧窝及少量准解理形貌，其韧性变差；调质+深冷处理后组织为铁素体+回火索氏体+贝氏体，组织更加细小、均匀且铁素体含量变多，相较未处理试样，硬度提高了22.52%,抗拉强度提升16.76%,深冷处理改善了调质态试样的塑性，拉伸断口为韧性断裂特征。更多还原

【Abstract】 Effects of cryogenic treatment, quenching and tempering, and quenching and tempering+cryogenic treatment on microstructure and mechanical properties of the X70 pipeline steel were studied by means of optical microscope, scanning electron microscope, microhardness tester, and universal electronic tensile test machine. The results show that the microstructure of the X70 pipeline steel without treatment is ferrite+pearlite. After cryogenic treatment only, the microstructure is finer and more uniform, the content of pearlite decreases, the microhardness and tensile strength of the X70 pipeline steel increase respectively by 2.73% and 9.58%, and the tensile fracture morphology is equiaxed dimples, showing a ductile fracture characteristic. After quenching and tempering, the microstructure of the X70 pipeline steel is ferrite+tempered sorbite+bainite, the hardness and tensile strength increase by 13.62% and 5.64%, respectively, compared to that of the untreated specimen, and the tensile fracture is distributed with dimples and a small amount of quasi cleavage morphologies, showing a decrease in toughness. After quenching and tempering+cryogenic treatment, the microstructure of the X70 pipeline steel is ferrite+tempered sorbite+bainite, the microstructure is finer and more uniform, the ferrite content increases, the hardness and tensile strength increase by 22.52% and 16.76%, respectively, compared to that of the untreated specimen, and the cryogenic treatment improves the plasticity of the quenched and tempered specimen, thus the tensile fracture exhibits ductile fracture characteristics.更多还原