Performance of Inductors Attached to a Galvanizing Bath
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DUCTION
THE hot dip galvanizing process is a complex metallurgical process. In a zinc alloy bath, a steel strip is rapidly immersed and continuously coated by zinc whose temperature is normally between 723 K and 753 K (450 °C and 480 °C) (see Figure 1).[1] The operation parameters of various galvanizing lines can vary considerably, including product specification, strip speed, strip temperature, bath configuration, bath chemistry, inductors, wiping systems, as well as chemistry, placement and dissolution pattern of ingots of zinc alloy.[1–3] For example, some operation parameters of the galvanizing line studied in this article from an Iron and Steel Co., Ltd are different from those found in literature. For a given hot dip galvanizing line, the flow field, the temperature field, and the dissolved aluminum (Al) and ferrum (Fe) concentration fields (Three Fields) in the bath can influence the dross formation and the coating quality of the steel strip surface. The Three Fields are mainly determined by the strip speed, strip temperature, strip dissolution, and heat dissipation through walls, inductors, and ingots of zinc alloy. Strip speed, strip temperature, and heat dissipation through walls can be modeled by setting appropriate boundary conditions. The simulation of ingots of zinc alloy has been performed by assuming an immersion pattern and a dissolution pattern. Ajersch et al.[4] assumed the ingots XINPING ZHOU, Associate Professor, is with the Department of Mechanics, Huazhong University of Science and Technology (HUST), Wuhan 430074, P.R. China. Contact e-mail: [email protected] SHUO YUAN, CHI LIU, and CHAOQUN QIAN, Postgraduate Students, are with the Department of Mechanics, Huazhong University of Science and Technology (HUST). PENG YANG, Engineer, is with the Wuhan Iron and Steel Co., Ltd, Wuhan 430074, P.R. China. BAO SONG, Associate Professor, is with the School of Mechanical Science and Engineering, Huazhong University of Science and Technology (HUST). Contact e-mail: [email protected] Manuscript submitted April 12, 2013. Article published online September 27, 2013. 1580—VOLUME 44B, DECEMBER 2013
are added to the bath at ambient temperature; at the sixth minute, the ingots are heated to the melting point and the ingots start to melt with the effective ingot mass flux acted as a parabolic function of time, and at the twentieth minute, all the zinc and the aluminum in the ingots are dissolved in the bath. Ilinca et al.[1] used the expression of the mean Al mass rate in the ingot melting volume as a negative linear function of the Al concentration in the bath. Al consumption on the strip surface is assumed to take place on the first 0.305 m of the strip length from its entry on the bath (corresponding to 0.2 seconds at a trip velocity of 1.524 m/s). The overall Al concentration of the coating is considered to be 0.4 pct by weight for a coating weight of 0.2 kg/m2 per side. Simulation of the inductors is one of the most important and complex parts of the bath; the inductors are referred as to magnetic field, electric
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