Improvement of Refining Method by using Reaction between Multi-component Mesoscopic Phase and Liquid Iron

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 13450305
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Metal making engineering
• Research Institution: Tohoku University
• Principal Investigator: SUITO Hideaki Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Professor, 多元物質科学研究所, 教授 (70030054)
• Co-Investigator(Kenkyū-buntansha): OHTA Hiroki Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Research Associate, 多元物質科学研究所, 助手 (20271976) ; INOUE Ryo Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Associate Professor, 多元物質科学研究所, 助教授 (70111309)
• Project Period (FY): 2001 – 2003
• Keywords: mesoscopic phase / refining / solid phase / precipitate

Research Abstract

In mesoscopic refining process, the dephosphorization rate is improved considerably due to high L_p^<solid/slag> value irrespective of solid/liquid mass ratio compared with a conventional slag refining, and slag consumption decreases theoretically. However, it is disadvantageous that only the diffusion area of about 1〜2mm length from the interface of metal/mesoscopic phase contributes to the dephosphorization reaction in mesoscopic refining process, while all slag is used in a slag refining process, and the dense layer is formed at the interface with the metal. Therefore, it is effective to inject the 1〜2 mm particles of the mesoscopic refining flux into liquid iron and to avoid the formation of dense layer.
Application of the mesoscopic refining process to steel dephosphorization is thought to be useful because of the small temperature dependence of L_p^<solid/slag>. Although L_p^<slag/metal> becomes disadvantageous at higher temperature, it can he improved by increasing CaO/SiO_2 ratio.
When the mesoscopic phase, in which C_2S particles precipitate by the carbon reduction of liquid slag, is used in hot metal dephosphorization, the size and dispersion of C_2S-C_3P particles are not related to the reactivity of the mesoscopic phase. It is important to keep the large content of FeO in slag after C_2S precipitation. The low reversion rate of P_2O_5 from the C_2S-C_3P (C_4P, C_3P) particles to slag is also advantageous.
In the present slag refining process, large amount of flux is used inevitably because the flux is not completely melted. In the use of mesoscopic refining flux obtained by the mixing-pressing method, the efficiency of refining becomes high because of the uniformity of mesoscopic refining flux. In the use of mesoscopic refining flux obtained by the precipitation method, in which cooling and/or carbon reduction technique is used, the efficiency of refining becomes higher because of the fine dispersion of solid phase in mesoscopic refining flux.