Hydraulics and Mathematics Simulation on the Weir and Gas Curtain in Tundish of Ultrathick Slab Continuous Casting
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N the steel continuous casting process, tundish is basically a vessel to supply and distribute liquid steel to different molds at an approximately constant rate. Recently, with emphasis on improving steel quality, the tundish has become more of a continuous reactor than a distribution vessel. Thus, the steel making tundish is designed to carry out more metallurgical operations such as inclusions separation, inclusions floatation, alloy trimming of steel, and thermal homogenization.[1–3] The continuous casting ultrathick slab, as one of the main constructive materials, has a wide range of use both in civil and military facilities, such as the gate of hydroelectric power station, offshore platform, the deck of the aircraft carrier, etc. Thus it requires very good steel quality with few large nonmetal inclusions in liquid steel at the last process of casting. Tundish is the best place to decrease inclusions in the continuous casting process. The flow pattern in tundish directly affects the floating of inclusions. However, Lopez-Ramirez et al.[4] have studied that the small nonmetallic inclusions do not have enough buoyancy force to float and reach to the slag layer. Thus, various kinds of flow-control devices[5–8] such as a dam, weir, baffles, turbulence inhibitor, and gas curtain, have been used in tundish to change the flow field, so as to increase DENGFU CHEN, Professor, XIN XIE and LEILEI ZHANG, Ph.D. Students, MUJUN LONG, Lecturer, MIN ZHANG, Master Student, and QI LIAO, Engineer, are with the Laboratory of Metallurgy and Materials, College of Materials Science and Engineering, Chongqing University, Chongqing 400030, P.R. China. Contact e-mail: [email protected] Manuscript submitted February 20, 2013. Article published online September 27, 2013. 392—VOLUME 45B, APRIL 2014
the residence time, decrease the dead volume area, and steady the steel flow of the injection zone. Finally, the inclusions were decreased. Koria and Singh[8] used a physical model to study the modifier and found the weir would produce a short circuiting, but the dam could eliminate this flow pattern. In the steel casting process, the weir is mainly used to divide the injection zone and pouring zone. This process is good for controlling the turbulence in the injection zone and benefits the inclusion float in pouring zone. In addition, the weir is irreplaceable for renewing the slag of injection zone in the sequence casting process. The gas curtain[5,9,10] is an important device for improving inclusions floatation because it can generate an upper flow with inclusions to slag layer and the inclusions are easy to float when absorbed by gas bubbles. Both of these qualities are a benefit for the removal of small (smaller than 100 lm) inclusions. Ramos-Banderas et al.[10] and Vargas-Zamora et al.[11] found that the small rates of gas injection through a gas curtain improved the fluid flow by enhancing the plug flow volume fraction. The high flow rates led to a thermal homogenization in two separated cells of flow located at each side of the gas curtain. Z. Meijie et al.[9] stu
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