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Fluoride evaporation and crystallization behavior of CaF2–CaO–Al2O3–(TiO2) slag for electroslag remelting of Ti-containing steels

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Abstract

To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF2–CaO–Al2O3–(TiO2) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO2-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO2-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO2-free slag melt, which is accompanied by CaF2 evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF2 crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO2 largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO2 addition leads to the precipitation of needle-like perovskite (CaTiO3) crystals instead of CaO crystals in the slag. The crystallization of perovskite (CaTiO3) occurs by bulk nucleation and diffusion-controlled one-dimensional growth.

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Authors and Affiliations

  1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing, 100083, China

    Cheng-bin Shi, Ding-li Zheng & Jing Li

  2. Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, 790-784, Korea

    Jung-wook Cho

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  1. Cheng-bin Shi
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  2. Jung-wook Cho
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  4. Jing Li
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Correspondence to Cheng-bin Shi or Jung-wook Cho.

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Shi, Cb., Cho, Jw., Zheng, Dl. et al. Fluoride evaporation and crystallization behavior of CaF2–CaO–Al2O3–(TiO2) slag for electroslag remelting of Ti-containing steels. Int J Miner Metall Mater 23, 627–636 (2016). https://doi.org/10.1007/s12613-016-1275-3

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  • DOI: https://doi.org/10.1007/s12613-016-1275-3

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