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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.

Microstructure and Precipitation of High Niobium Pipeline Steel

Microstructure evolution and precipitation behavior of high niobium pipeline steel produced by thermomechanical controlled processing were investigated by scanning electric microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). Experimental results show that fine grains were obtained in high niobium pipeline steel strip. The grains consisted of acicular ferrite with high dislocation density, martensite-austenite (M/A) constituent and a few of polygonal ferrite. And the precipitates in trail steel were observed, and undissolved TiN during reheating, NbC of strain-induced precipitation and NbC dispersedly precipitated within ferrite matrix at lower temperature. The combination of high strength and toughness is attributed to the fine effective grain size and the interaction between high density dislocation and dispersedly precipitation phase.