Generating Mechanism of Large Heterogeneous Carbonitrides with Multiple Layers in H13 + Nb Bar

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• 作者：You Xie ; Guoguang Cheng ; Lie Chen ; Yandong Zhang and Qingzhong Yan
• 刊名：steel research international
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：88
• 期：1
• 全文大小：2235K
• ISSN：1869-344X

文摘

The characteristics and generating mechanism of heterogeneous carbonitride with micron size in H13 + Nb bar are studied. Three types of precipitates are observed according to the number of layers, that is, two-layer ones, three-layer ones, and four-layer ones. Two-layer precipitate contains the oxide core and the outer Ti–V-rich carbonitride, while three-layer precipitate has one more Nb-rich carbonitride at the outside. Four-layer precipitate has a V-rich carbonitride at the outmost layer besides the inner three types of phases similar to that in the three-layer precipitate. The size of these large precipitates can be even up to tens of microns. The oxide cores are mainly stoichiometric spinel MgAl₂O₄ and generated in the liquid steel before solidification. The compositional characteristics and precipitating sequence of carbonitride can be well explained through calculation by Scheil–Gulliver model in Thermo-Calc. Ti–V-rich phase precipitates first during solidification, after which Nb-rich phase and V-rich phase precipitates successively. Some dissolution occurs between the different layers during the following temperature reducing and heating treatment process.