Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
Microsc Microanal. 2013 Aug;19 Suppl 5:62-5. doi: 10.1017/S1431927613012348.
Precipitates in two X80 pipeline steels were studied by transmission electron microscopy equipped with an energy filtering system. The steels are microalloyed with niobium and niobium-vanadium (Nb-V), respectively, and produced by continuous hot rolling. Besides the precipitates TiN and (Ti, Nb) (C, N), which were 10-100 nm in size, a large number of precipitates smaller than 10 nm distributed in the two steels have been observed. In the Nb-V microalloyed steel, only a few titanium nitrides covered by vanadium compounds on the surface have been observed. It is inferred that the vanadium exists mainly in the matrix as a solid solution element. The fact has been accepted that there was no contribution to the precipitation strengthening of the X80 steel by adding 0.04-0.06% vanadium under the present production process. By contrast, the toughness of the Nb-V steel is deteriorated. Therefore, a better toughness property of the Nb microalloyed X80 results from the optimum microalloying composition design and the suitable accelerating cooling after hot rolling.
采用带有能谱分析系统的透射电子显微镜研究了两种 X80 管线钢中的析出相。这两种钢分别采用铌和铌-钒（Nb-V）微合金化，通过连续热轧生产。除了尺寸为 10-100nm 的 TiN 和（Ti，Nb）（C，N）析出相之外，还观察到大量尺寸小于 10nm 的析出相分布在这两种钢中。在 Nb-V 微合金钢中，只观察到表面有少量被钒化物覆盖的钛氮化物。由此推断，钒主要以固溶体形式存在于基体中。事实已经被接受，即在目前的生产工艺下，添加 0.04-0.06%的钒对 X80 钢的析出强化没有贡献。相比之下，Nb-V 钢的韧性恶化了。因此，Nb 微合金化 X80 的更好韧性性能归因于最佳的微合金化成分设计和热轧后合适的加速冷却。
