Precipitation behaviors of X80 acicular ferrite pipeline steel

Ai-min Zhao1), Yan Wang1), Yin-li Chen1), Di Tang1), Xu-tao Gao1), and Bi-qiang Zuo2) 1) Research Institute of Metallurgy Engineering, University of Science and Technology Beijing, Beijing 100083, China 2) Rolling Mill Business Division, WISDRI Engineering & Research Incorporation Limited Company, Wuhan 430223, China

摘 要：The precipitation behaviors of X80 acicular ferrite pipeline steel were investigated by using transmission electron microscopy （TEM） and energy dispersive spectroscopy （EDS）. The results show that dendritic precipitates in the as-cast steel slabs precipitate mainly in grain boundaries, and these dendritic precipitates dissolve and re-precipitate to two kinds of carbonitrides: Ti- and Nb-rich （Ti, Nb）（C, N） carbonitrides during reheating. Four types of precipitates mainly exist in the hot rolled plate: Ti-rich carbonitrides resulted from the dendritic carbonitrides undissolved during the reheating process; Ti-rich carbonitrides re-precipitated along austenite grain boundaries during the re-heating process; NbC carbides mainly heterogeneously nucleated on the small pre-existing Nb-rich carbonitrides in the hot rolling process; and NbC carbides precipitated on dislocations during hot rolling.

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