微合金化技术开发800MPa级高韧直缝焊管钢

采用微合金化和热轧后超快冷等技术生产得到800 MPa级高韧直缝钢管钢，借助OM、SEM、TEM和室温拉伸等，研究了试验钢不同区域的组织与性能。研究表明，试验钢的热轧组织主要是粒状贝氏体+少量板条贝氏体；焊接热影响区粒状贝氏体体积分数减少到32.7%,板条贝氏体体积分数增加到30.5%,组织中出现针状铁素体和少量马氏体。试验钢热轧区主要以Ti为主进行复合微合金化，综合运用固溶强化、细晶强化、位错强化和析出强化，具有高的强韧性，屈服强度为804 MPa、抗拉强度为852 MPa、伸长率为21.5%。

Development of 800 MPa grade microalloyed steel for high toughness longitudinal welded pipe

800 MPa high-toughness microalloyed steel longitudinal welded pipe was produced by ultra-fast cooling after hot rolling. Microstructure and properties of different regions of the tested steel were studied by means of OM, SEM, TEM and tensile testing. The results show that the hot-rolled structure of the tested steel is mainly granular bainite+a small amount of lath bainite, the amount of granular bainite in the welding heat affected zone reduces to 32.7%, and the lath bainite increases to 30.5%, acicular ferrite and a small amount of martensite appear in the microstructure. The hot rolling zone of the tested steel is mainly composed of Ti for composite microalloying, and the comprehensive application of solution strengthening, fine grain strengthening, dislocation strengthening and precipitation strengthening, the yield strength, tensile strength, and elongation are 804 MPa, 852 MPa and 21.5%, and shows high strong toughness.