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通过采用扫描电镜、透射电镜及电子能谱等分析测试技术,研究了高铌管线钢的显微组织特征和析出相种类、大小及形态。结果表明,采用控轧控冷工艺(TMCP)生产的高铌管线钢具有细化的显微组织和多种类型的析出相,显微组织主要为高位错密度的针状铁素体、少量多边形铁素体和MA岛;第二相粒子主要包括板坯再加热过程中未溶解的TiN、以TiN为核心的高温析出NbC、形变诱导析出的NbC和低温弥散析出的细小NbC。细化的有效晶粒尺寸,以及高密度位错与弥散析出相间的交互作用,确保了高铌管线钢获得高的强度和韧性。
The microstructure and the type, size and morphology of the precipitated phase in high niobium pipeline steel were studied by means of scanning electron microscopy, transmission electron microscopy and electron spectroscopy. The results show that high niobium line steel produced by controlled rolling and controlled cooling process (TMCP) has refined microstructure and many types of precipitates. The microstructure is mainly acicular ferrite with high dislocation density and a few polygons Ferrite and MA island. The second phase particles mainly include undissolved TiN during slab reheating, NbC precipitated by TiN, NbC induced by deformation and fine NbC precipitated by low temperature. The refinement of the effective grain size, as well as the interaction between high-density dislocations and disperse precipitates, ensures high niobium line steels achieve high strength and toughness.