Mathematical Modeling on the Growth and Removal of Non-metallic Inclusions in the Molten Steel in a Two-Strand Continuou
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CONTINUOUS casting tundish serves as a buffer and acts as distributors of the molten steel between the ladle and the mold. It shows various metallurgical functions, such as optimization of molten steel flow, inclusions separation, alloy trimming of steel, superheat control, and thermal homogenization. Nowadays, to realize an optimal flow and better cleanliness of the liquid steel, the design of the tundish needs to meet the targets of (1) high average residence time; (2) small dead volumes and non-short circuit flow; (3) large volume of laminar flow region; (4) forced collision of inclusions in suitable turbulent zones and floating of inclusions at other zones, assimilated by the cover slag; and (5) avoiding the excessive top surface level fluctuation and reoxidation by air absorption.
HAITAO LING, Ph.D. Student, and LIFENG ZHANG, Professor, are with the Beijing Key Laboratory of Green Recycling and Extraction of Metals (GREM), University of Science and Technology Beijing (USTB), Beijing 100083, China, and also with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB). Contact e-mail: [email protected] HONG LI, Professor, is with the School of Metallurgical and Ecological Engineering of University of Science and Technology Beijing (USTB). Manuscript submitted February 17, 2016. Article published online July 12, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
Flow control devices, such as weirs, dams, turbulence inhibitors, and baffles, have been installed at suitable positions in the tundish, with a purpose to improve the flow pattern of the molten steel and promote the removal of inclusions. A large number of inclusions, especially coagulated large-sized ones, have a detrimental effect on the quality of steel products. Steel cleanliness depends greatly on the amount, the size distribution, morphology, and composition of non-metallic inclusions in the steel. They should be under strict control during the production of high clean steels. An extensive review in the evaluation and control of steel cleanliness has been made by the current author, Zhang and Thomas, in 2003.[1] According to the steel grade and its end use, the requirements of steel cleanliness are different. For instance, the total oxygen and maximum size of inclusions for ball bearings are needed to be less than 10 ppm and 15 lm, respectively,[2–4] and they are required to be less than 15 ppm and 10 lm for tire cord steels.[2] Many defects in the steel products caused by inclusions are mentioned in the literature. Lange[5] found that the cracked flanges were caused by sulfide and oxide inclusions in the low carbon Al-killed steel. Park and Todoroki[6] reported that swollen defects on a deeply draw product were induced by MgOÆAl2O3 spinel inclusions. Van Ende et al.[7] found that the submerged entry nozzle was seriously clogged due to the accumulation of Al2O3 inclusions generated by reoxidation using the population density VOLUME 47B, OCTOBER 2016—2991
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