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介绍了一种900 MPa的含铌超低碳高强管线钢,其显微组织主要是贝氏体与针状铁素体,含有一些少量的M-A岛,其中贝氏体比例最大。经显微检测,其平均晶粒尺寸为3.21μm,板条状贝氏体厚度约200 nm,Nb和Ti的微小析出相可以在晶界处和晶体内部析出,且快冷能抑制Nb和Ti的碳化物析出。该钢的-20℃夏比冲击吸收功为200 J,伸长率为15%,屈服比小于0.84,这种高强度低屈服比的完美结合是通过控轧控冷的工艺来实现的。
A kind of 900 MPa niobium ultra low carbon high strength pipeline steel is introduced. Its microstructure is mainly bainite and acicular ferrite. It contains some minor M-A islands with the largest proportion of bainite. After microscopic examination, the average grain size is 3.21μm and the lath bainite thickness is about 200 nm. The micro-precipitates of Nb and Ti can be precipitated at the grain boundaries and inside the crystal, and the rapid cooling can restrain the growth of Nb and Ti Of carbide precipitation. The steel has a Charpy impact energy absorption of 200 J at -20 ° C, an elongation of 15% and a yield ratio of less than 0.84. This perfect combination of high strength and low yield ratio is achieved by a controlled rolling and controlled cooling process.