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Characteristics of Deoxidation and Desulfurization during lf refining Al-killed Steel by Highly Basic and Low Oxidizing Slag

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Journal of Iron and Steel Research(International) 2014年第2期21卷 166-173页

作者： Jing GUO Shu-sen CHENG Zi-jian CHENG State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological EngineeringUniversity of Science and Technology of Beijing Jiuquan Iron and Steel (Group) Co. Ltd.

Steel and slag samples were taken at the start and the end of lf refining for steel plate cold common （SPCC）, in the compact strip production （CSP） process, and at the same time, the temperature and oxygen activity a[o] were measured by using an oxygen sensor. Furthermore, inclusions in steel samples were monitored by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It was confirmed that a [o] in liq- uid steel was in equilibrium with inclusion rather than with top slag during lf refining. Desulfurization was related to deoxidation since a[o] at slag-steel interface was clarified to be very close to that in liquid steel under the specific con- dition in lf with intense stirring by argon blowing and refined by highly basic low oxidizing slag for Al-killed steel. Sulfur partition ratio （Ls） was very sensitive to a[o]. Since a[o] increased rapidly with temperature rise, it not only offset promotion to desulfurization reaction with temperature rise but decreased Ls. For Al-killed steel, the.modifica- tion of Al2O3 for lowering the activity of Al2O3 in inclusion was believed to be favorable for both deoxidation and desulfurization during lf refining.

关键词： deoxidation desulfurization inclusion sulfur partition ratio lf refining

Inclusion Composition Control During lf refining for SPCC Using FactSage Combined With Industrial Trials

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Journal of Iron and Steel Research(International) 2013年第2期20卷 14-20页

作者： CHENG Zi-jian GUO Jing CHENG Shu-sen State Key Laboratory of Advanced Metallurgy School of Metallurgy and Ecology Engineering University of Science and Technology Beijing Hongxing Iron and Steel Co Ltd

Steel plate cold common （SPCC） is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects reduction during rolling. Thus it is essential to understand steel-inclusion equilibrium since inclusion composition is determined by composition of liquid steel directly through steel-inclusion reaction. Thermodynamic calculation software FactSage is performed to understand how to control inclusion composition during ladle furnace （lf） refining, and industrial trials are carried out to verify calculated results. Firstly, target region for controlling CaO-Al2O3-MgO ternary inclusion is analyzed on the basis of the ternary phase diagram and the relationship between activities related to pure solid and activities related to pure liquid was fixed by thermodynamic analysis in order to obtain reliable activities for components of inclusions in the target region by FactSage. In addition, inclusions in steel samples are detected by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It is found that most of Al2O3 inclusions are modified into lower melting point region but a number of them are still located in high melting point region at the end of lf refining after Ca-treatment. Moreover, the composition of liquid steel equilibrating with liquid CaO-Al2O3-MgO inclusion is obtained by steel-inclusion equilibrium calculation when w[Al]s is approximating 0.03% as： a[O] is 1.0×10-6 to 4.0×10-6, w[Ca] is 20×10-6 to 50×10-6 and w[Mg] is 0.1×10-6 to 3.0×10-6. At last, stability diagrams of various calcium aluminates and CaS are established and they show that liquid calcium aluminate inclusions form when w[Ca] is more than 20×10-6, but CaS precipitation is difficult to prevent because sufficiently low w[S] （〈0.003%） is required.

关键词： lf refining inclusion control steel-inclusion equilibrium FactSage

Thermodynamic Analysis of Desulfurization and Its Connection With Deoxidation and Temperature for SPHC in JISC During lf refining Process

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Journal of Iron and Steel Research(International) 2011年第S2期18卷 135-140页

作者： GUO Jing1, CHENG Zi-jian1,2, CHENG Shu-sen1, CHENG Ze-wei1, ZOU Ming2, MA Ming-sheng2 (1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology of Beijing, Beijing 100083, China 2. China’s Hongxing Stock Company of Jiugang,Jiugang 735000,Gansu,China) Univ Sci & Technol Beijing State Key Lab Adv Met Beijing 100083 Peoples R China Chinas Hongxing Stock Co Jiugang Jiugang 735000 Gansu Peoples R China

The thermodynamic characteristics of desulfurization reaction (CaO)+[S]=(CaS)+[O] is analyzed based on the detailed composition of liquid steel and slag of Steel Plate Hot Commercial (SPHC) in Jiuquan Iron & Steel Corporation(JISC), where the activities of CaO, CaS and Al2O3 in molten slag are calculated by thermodynamic software FactSage for a more accurate result. The critical values of [O%]/[S%] for desulfurization at different temperature is are obtained, typically 0.09 at 1873K, which shows directly that it should deoxidize adequately for obtaining a favorable desulfurization condition. In addition, the thermodynamic analysis indicates that the actual dissolved O is much higher than that of equilibrium calculation which shows Al-O reaction in lf is far away from equilibrium, but it is perfect agreement with the computing results when taking the activity of Al2O3 as 1 that due to the inclusion component in lf is mainly Al2O3. Besides, with the temperature rise, the sulfur partition ratio increases softly meanwhile the reaction between Al and O is limited to a great degree resulting in the increase a dissolved oxygen in liquid steel that decreases the sulfur partition ratio seriously. As a result, the sulfur partition ratio appears to decrease with temperature increase in Al killed steel.

关键词： lf refining desulfurization deoxidation sulfur partition ratio

Application of Alumina-magnesia Precast Blocks for lf refining Ladle

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Application of Alumina-magnesia Precast Blocks for LF Refini...

Development of an improved CBR model for predicting steel temperature in ladle furnace refining

中国材料大会2012

作者： Haixia Feng Jun Liu Yi Wei Sinosteel Corporation Luoyang Institute of Refractories Research Co. Ltd State Key Laboratory of Advanced Refractories

ISBN: (纸本)9783037856079

The alumina-magnesia precast blocks developed in author’s company have been successfully used in 90-ton lf refining with an average service life 80-85 heats to meet the smelting demand of low carbon steel and ultra low carbon steel. The observation of the residual blocks revealed that the section of the used blocks was divided into four layers from inside to the surface, i.e., slag layer, reaction layer, penetration layer and the original block. It has been found that there was a certain degree of structure spalling of the used blocks. The main factor of blocks’ damage may be due to the penetration and erosion of molten slag. The results of SEM microstructure analysis indicated that the calcium oxide(CaO) of high basicity slag easily penetrated into the blocks and formed CA6 phase, and then transformed into CA2 or C12A7 phases gradually with the decreasing content of alumina (Al2O3 ). It has been found that an annular distribution structure, and the silicon dioxide (SiO2 ) was easily lost together with slag and formed SiO2 -rich part in the penetration layer due to the formation of low viscosity and low melting point phase of C2 AS. A large number of -5um spinel particles (MgAl2O4 ) were synthesized at 16001700℃, which could absorb FeO, MnO and other impurities in slag to form composite spinel phase. It is believed that the high melting point phases intertwined to form a dense area which was beneficial to improve the bricks’ slag resistances to penetration and corrosion

关键词： Alumina-magnesia Precast block lf refining Penetration.

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International Journal of Minerals,Metallurgy and Materials 2021年第8期28卷 1321-1331页

作者： Fei Yuan An-jun Xu Mao-qiang Gu School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China

In the prediction of the end-point molten steel temperature of the ladle furnace, the influence of some factors is nonlinear. The prediction accuracy will be affected by directly inputting these nonlinear factors into the data-driven model. To solve this problem, an improved case-based reasoning model based on heat transfer calculation(CBR-HTC) was established through the nonlinear processing of these factors with software Ansys. The results showed that the CBR-HTC model improves the prediction accuracy of end-point molten steel temperature by5.33% and 7.00% compared with the original CBR model and 6.66% and 5.33% compared with the back propagation neural network(BPNN)model in the ranges of [-3, 3] and [-7, 7], respectively. It was found that the mean absolute error(MAE) and root-mean-square error(RMSE)values of the CBR-HTC model are also lower. It was verified that the prediction accuracy of the data-driven model can be improved by combining the mechanism model with the data-driven model.

关键词： case-based reasoning lf refining steel temperature prediction ladle lining

Effects of ferrosilicon alloy,Si content of steel,and slag basicity on compositions of inclusions during ladle furnace refining of Al-killed steel

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Journal of Iron and Steel Research(International) 2020年第9期27卷 1011-1017页

作者： Jian-fei Xu Kun-peng Wang Ying Wang Zhi-dong Qu Xing-kuang Tu Zenith Steel Group Co. Ltd.Changzhou 213000JiangsuChina

To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace(lf)refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing,the effects of ferrosilicon alloy,Si content of steel,and slag basicity on the compositions of inclusions during lf refining were investigated in Al-killed steel.Al2O3 inclusions could be transformed into CaO-Al2O3-MgO-CaS inclusions after adding ferrosilicon alloy in the lf refining process as this alloy contains some CaSi alloy impurities.The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions.Si in liquid steel had a significant influence on the compositions of inclusions during lf refining when CaO-Al2O3-SiO2-MgO slag with high basicity of 7.0 was used.This was because[Ca]produced by the reaction of CaO and[Al]could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel,which was confirmed by the difference of total calcium content between Si-free and Si-containing steels.As a result,Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel,whereas calcium aluminate inclusions were found in Si-containing steel.For CaO-Al2O3-SiO2-MgO slag with low basicity of 2.8,Al2O3 and MgO·Al2O3 inclusions were obtained after lf refining in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process.This was because the reaction of CaO and[Al]was weak,and residual[Ca]in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2,leading to a low total calcium content of 0.0003%in Si-containing steel.

关键词： Inclusion Ferrosilicon alloy Si content Basicity lf refining

Evolution of Nonmetallic Inclusion during Steelmaking Process of Cold Heading Steel SWRCH35K

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Journal of Minerals and Materials Characterization and Engineering 2022年第5期10卷 438-445页

作者： Mengxiong Li Qi Xu Jianli Li No. 2 Steel-Making Plant Jiangsu Yonggang Group Co. Ltd. Zhangjiagang China Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and Technology Wuhan China

In order to analyze the evolution of the inclusions in the cold heading steel SWRCH35K during the steelmaking process, a systematic sampling of the steelmaking processes in a steel plant was carried out. Both SEM-EDS and the image processing software Image-Pro-Plus6.0 were employed to analyze the chemical composition, morphology, quantity and size of non-metal inclusions in the steel samples. The results show that from BOF tapping to continuous casting tundish, the composition of inclusions in SWRCH35K steel changes from Al2O3 →MgO·Al2O3 →CaO-MgO-Al2O3-CaS, and the typical morphology of the inclusions in the steel gradually changes from irregular blocks and clusters to spherical. The number of inclusions in the BOF argon blowing station is the largest, 213#/mm2, while the number of inclusions at the end of lf refining is the least, about 12#/mm2, and there are basically no inclusions above 5 μm. In addition, lf calcium treatment will adversely affect the size and quantity control of inclusions in steel. In order to effectively reduce the large-size calcium-containing spherical oxide inclusions in cold heading steel, it is necessary to find a technical method that can replace lf calcium treatment to solve the problem of molten steel continuous casting.

关键词： Cold Heading Steel Inclusions lf refining Calcium Treatment