Principles in cast rolling with liquid core of thin slab continuous casting
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I. INTRODUCTION
THE development in continuous casting and hot rolling has been strongly dominated by the demands of quality improvement and reduced costs for steel products in recent years. To achieve these goals, consideration has been given to shortening the production line by connecting the casting and deformation processes.[1] Various new thin slab casting processes are being developed and explored with experimental or pilot casters around the world. The Inline Strip Production (ISP) process of Mannesmann Demag (MDH) is an exemplary one, which was first commercialized at Arvedi in Italy. The rolling process of the casting slab with its core still being liquid or mushy state within the machine is often termed as cast rolling with liquid core. One of the main characteristics of thin slab casting in the ISP process is dynamic strand guiding for cast rolling with liquid core. As schematically shown in Figure 1, even just below the mold in this process, strand thickness is reduced by means of the tapered roll guide configuration of the segment “0.” A further strand reduction with liquid core to approximately 40 mm is to be achieved within the multiple roller segments by means of many hydraulically adjustable roller pairs. Because the casting speed is constant during cast rolling with liquid core in the ISP thin slab casting process, there is no elongation of strand during cast rolling with liquid core.[2] Wunnenberg and Schwerdtfeger introduced the experiments performed by Eisermann and deduced some important conclusions for the real process from the laboratory simulation.[3] The decrease in the strand thickness with a liquid (or mushy) core will occur mainly by outward bulging of the narrow sides. There is some real rolling action with longitudinal mass flow that starts primarily at the edges and then is transferred by shear from the edges toward the overall broad sides. Hence, some longitudinal tensile strain develops. But, this strain was only about 1 pct at a thickness ZHOUWEI LU, Lecturer, is with the Department of Mechanical and Electrical Engineering, Zhengzhou University, Zhengzhou, 450052, Henan Province, People’s Republic of China. (E-mail: [email protected]) KAIKE CAI, Professor, and JIAQUAN ZHANG, Associate Professor, are with the Institute of Steelmaking, University of Science and Technology Beijing, Beijing, 100083, People’s Republic of China. Manuscript submitted March 30, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
reduction of 20 pct in the laboratory experiment. This kind of phenomenon probably will even decrease with the increasing width of the strand. It seems fortunate that the strand reduces its thickness almost completely by the bulging of the narrow sides. If the bulging would not occur, that is, if the thickness reduction was caused by the rolling of the edges alone, the longitudinal tensile strain imposed on the shell of the broad sides would be large, then causing a danger of transverse tearing in low ductility steels. However, Cremer et al. pointed out that, depending on the thickn
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