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利用光学显微镜、扫描电镜和透射电镜等方法,研究了回火工艺对含V超高强度管线钢组织与力学性能的影响。结果表明,随着回火温度的升高和回火时间的延长,试验钢的强度先上升再降低,伸长率和屈强比增加,冲击性能降低。这主要是由于回火后位错密度降低、M/A岛(martensite-austenite)分解、NbC/Nb(CN)与VC/V(CN)等析出相的形成及聚合长大等因素造成。在600℃×60 min的回火条件下,试验钢综合力学性能优良,其屈服强度、抗拉强度和-20℃冲击吸收能量分别是671 MPa、755 MPa和177 J,均达到超高强度管线钢X100的要求。
The effects of tempering process on the microstructure and mechanical properties of V-containing ultra-high strength pipeline steel were studied by means of optical microscope, scanning electron microscope and transmission electron microscope. The results show that with the increase of tempering temperature and tempering time, the strength of the test steel first increases and then decreases, and the elongation and yield ratio increase, and the impact performance decreases. This is mainly due to the decrease of the dislocation density after the tempering, martensite-austenite decomposition, the formation of precipitates such as NbC / Nb (CN) and VC / V (CN) and the polymerization and growth. Under the condition of tempering at 600 ℃ for 60 min, the mechanical properties of the test steel are excellent, and the yield strength, tensile strength and impact energy absorption at -20 ℃ are 671 MPa, 755 MPa and 177 J, respectively, reaching ultra-high strength pipelines Steel X100 requirements.