论文部分内容阅读
采用扫描电镜、电子背散射衍射技术和常规力学性能测试等手段研究了两种X70管线钢的显微组织和力学性能。结果表明:管线钢的低温韧性不仅与其有效晶粒尺寸有关,而且还与其组织中的马奥岛和析出相有关;但是,与管线钢中大角度晶界所占的百分比没有直接的关系。有效晶粒尺寸越小,马奥岛和富钛氮化物数量越少、尺寸越小,管线钢的低温韧性就越好。富铌碳化物与高密度的位错和亚结构不仅能提高管线钢的屈服强度,而且还能增大其加工硬化速率,从而使其抗拉强度明显升高,屈强比减小。由此可见,通过显微组织的优化,可以得到高强度高韧性的管线钢。
The microstructure and mechanical properties of two kinds of X70 pipeline steel were studied by scanning electron microscopy, electron backscatter diffraction and conventional mechanical properties testing. The results show that the low temperature toughness of pipeline steel is not only related to its effective grain size, but also to the island and precipitates in its organization. However, it is not directly related to the percentage of large-angle grain boundaries in pipeline steels. The smaller the effective grain size, the smaller the island of Ma’oa and the amount of titanium-rich nitrides, the smaller the size, the better the low temperature toughness of the pipeline steel. Niobium carbide with high density of dislocations and substructures not only increases the yield strength of pipeline steels, but also increases the work hardening rate, resulting in a significant increase in tensile strength and a decrease in yield ratio. Thus, through the optimization of the microstructure, can be high strength and high toughness of the pipeline steel.