Modeling of the solidification process in a continuous casting installation for steel slabs
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INTRODUCTION
NOWADAYS almost 90 pct of the world steel production is being produced in continuous casting installations;[1] therefore, this is a technology with a very important economical impact. The continuous casting technology, which was originated almost 50 years ago and which in 1970 attained only 4 pct of the world steel production,[1] is still undergoing important developments due to the fact that the requirements on the product quality and on the production efficiency are continuously being increased. These developments incorporate not only equipment revamps but also updates in the installation setups and in their process controls. The first requirement to develop a successful setup and a tight control of any process is to have an in-depth knowledge of the process technological windows, that is to say, of the locus in the space of the process control variables, where the products meet the required specifications.[2,3] Computational models are nowadays a powerful and reliable tool to simulate different thermomechanical-metallurgical processes; hence, they are increasingly being used to investigate the technological windows of different processes in the steel industry, such as continuous casting, hot rolling, cold rolling, heat treatments, etc.[4] A schematic representation of a continuous casting installation for steel slabs in shown in Figure 1, where we can identify the following process sequence: (1) The liquid steel is poured into a copper mold, which is refrigerated with an external water jacket. The cooling of the steel and its solidification inside the mold MARCIAL GONZALEZ, Research Engineer, MARCELA B. GOLDSCHMIT, Head, Computational Mechanics Department, ANDREA P. ASSANELLI, Head, Full Scale Testing Laboratory, and EDUARDO N. DVORKIN, General Director, are with the Center for Industrial Research, FUDETEC Av. Córdoba 320 1054, Buenos Aires, Argentina. Contact e-mail: [email protected] ELENA FERNÁNDEZ BERDAGUER, Professor, is with CONICET, Instituto de Calculo, Science School, University of Buenos Aires, Ciudad Universitaria– Pabellón 2, Buenos Aires, Argentina. Manuscript submitted July 24, 2002. METALLURGICAL AND MATERIALS TRANSACTIONS B
progress from the outside to the inside; therefore, the external solidified steel shell increases its thickness as the steel strand transits the mold. The physical process inside the mold is quite complex because the solidified steel shell and the mold are strained due to thermal and mechanical loads (ferrostatic pressure). While at the meniscus the steel is in contact with the mold intrados, downstream, a gap is opened between the strand and the mold. However, in some cases, the mold is shaped so as to regain its contact with the strand at its lower sections.[5] Usually, the slab molds are equipped with thermocouples located through the thickness of its copper piates; the indications of these thermocouples are the input to a heuristic algorithm that provides break-out alarms. The mathematical description of the heat transfer between the strand and the mold req
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