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Contenu archivé le 2019-03-15

LUBRICATION OF THE CONTINUOUS CASTING OF STEELS BY SLAGS

Objectif



CONTINUOUS CASTING OF STEELS CONSUMES LESS ENERGY COMPARED TO CLASSICAL CASTING ROUTES, INCLUDING INGOT CASTING AND ROLLING. THIS PROJECT AIMS TO IMPROVE THE LUBRICATION OF THE CONTINUOUS CASTING OF STEELS.

PRESENT PRACTICE IS BASED LARGELY ON EXPERIENCE AND HAS GENERALLY NOT BEEN STUDIED UNDER WELL DEFINED CONDITIONS. IN A PREVIOUS THEORETICAL STUDY OF THE LUBRICATION OF CONTINUOUS CASTING, MADE IN CONJUNCTION WITH IRSID AND CEMEF, THE CALCULATED INFLUENCE OF THE SPEED OR THE VISCOSITY WAS NOT IN AGREEMENT WITH EXPERIMENTAL RESULTS.

ARMINES HAS NOW BUILT A RELIABLE COMPUTER MODEL OF THE LUBRICATION BY SLAGS, OF THE CONTINUOUS CASTING OF SLABS BY COUPLING A THERMAL ANALYSIS OF THE SYSTEM WITH A MODEL OF THE VISCOUS FLOW OF THE SLAG BETWEEN SHELL AND MOULD. THE MODEL PREDICTS THE INFLUENCE OF THE SLAG PROPERTIES ON THE HEAT FLUX EXTRACTED BY THE MOULD, THE FRICTION BETWEEN THE MOULD AND THE STEEL SHELL, AND THE DEFECTS OF THE CAST PRODUCTS.

THE THEORETICAL MODEL PROVIDED A GOOD ESTIMATE OF THE THERMAL FLUX EXTRACTED BY THE MOULD FOR LOW AND HIGH VISCOSITY SLAGS. COMPARISON OF THE MODEL WITH EXPERIMENTS SUGGESTS THAT THE FUSION PROCESS OF THE SLAG ABOVE THE MENISCUS CONTROLS ITS FLOW RATE AT HIGH VISCOSITY OR CASTING SPEED. MOREOVER, THE PREDICTED INFLUENCES OF THE CASTING SPEED AND THE SLAG VISCOSITY ON THE CONSUMPTION AND FRICTION, HAVE BEEN QUALITATIVELY IN GOOD AGREEMENT WITH INDUSTRIAL OBSERVATIONS.

THE MODEL PROVIDED AN EXPLANATION FOR SOME SURFACE DEFECTS DUE TO TOO HIGH VISCOSITY SLAGS WHOSE FLOW RATE IS CONTROLLED BY THE MELTING RATE. IT INDICATED THAT MOULD OSCILLATIONS DO NOT HAVE MUCH DIRECT INFLUENCE ON CONTINUOUS CASTING. IT ALSO SHOWED THAT THE VISCOSITY OF OPTIMAL SLAGS DECREASED AS THE CASTING SPEED INCREASED (SINCE AT HIGH SPEED, VISCOUS SLAGS INDUCE HIGH MOULD SURFACE TEMPERATURES WHICH IN TURN ARE PERHAPS RESPONSIBLE FOR HIGH WEAR, THE GENERATION OF HIGH FRICTION AND THE FORMATION OF A VERY THIN SHELL WHICH IS PRONE TO BREAKAGES.

IT IS BELIEVED THAT THE MODEL WILL IMPROVE THE CONTROL OF CONTINUOUS CASTING, PROVIDING PROPER CHOICE OF SLAGS MINIMISING THE SURFACE DEFECTS OF THE SLABS, THE BREAKAGE OF LUBRICANT FILM AND THE MOULD WEAR

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Coordinateur

SOCIETE ARMINES
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60 BOULEVARD SAINT-MICHEL
75272 PARIS
France

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