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采用光学和扫描电子显微镜过对X80大变形管线钢在拉伸和冲击载荷下的变形和断裂过程的实验观察,研究了X80大变形管线钢的变形和断裂行为。结果表明:对于由贝氏体+铁素体组成的双相大变形管线钢,在变形过程中,塑性变形优先在铁素体中进行,随着塑性变形量的增加,双相组织的形态逐渐沿作用力方向呈现明显的位向分布。双相组织中裂纹的产生有3种典型方式,即夹杂物形核、相界面形核以及铁素体或贝氏体基体形核。裂纹的扩展与所受的应力状态有关,在较低应力状态下时,裂纹主要通过铁素体扩展;只有在较高应力状态下,裂纹才穿越贝氏体。在实验观察和分析基础上建立了贝氏体+铁素体大变形管线钢的变形和断裂模型。
The deformation and fracture behavior of X80 large deformation pipeline steel under tension and impact loading were investigated by optical and scanning electron microscope. The deformation and fracture behavior of X80 large deformation pipeline steel were investigated. The results show that plastic deformation is preferentially performed in ferrite during the deformation process of billet large deformation pipeline steel composed of bainite and ferrite. With the increase of plastic deformation, the morphology of the dual phase structure gradually increases Along the force direction showed a significant distribution of orientation. There are three typical ways to produce cracks in the dual phase structure, inclusions nucleation, phase interface nucleation and nucleation of ferrite or bainite matrix. The crack propagation is related to the stress state experienced. In the lower stress state, the crack propagates mainly through ferrite. The crack propagates through the bainite only at higher stress. Based on the experimental observation and analysis, the deformation and fracture models of bainitic and ferritic large deformed pipeline steel were established.