Transient heat transfer between solidifying light metals strips and a moving substrate has been investigated. For this purpose, an experimental apparatus was constructed, consisting of a cold moving substrate onto which molten metal from a containment mold is deposited. The substrate was flame sprayed with various commercial coatings while its speed and the thicknesses of strip produced matched industrial values. The primary objective of this work was to study the effects of some important variables, such as roughness of substrate, type of coating, thickness of strip and initial superheat, on heat fluxes. Substrate speeds in the range of 0.4-1.2 m/s were employed and strips with thicknesses between 1 and 5 mm were produced. The heat fluxes were determined "inversely" by an inverse heat transfer technique, using temperature measurements from thermocouples embedded within the substrate. Peak heat fluxes between 0.6 and 3.0 MW/m 2 were found for the diverse experimental conditions investigated. The heat transfer coefficients were deduced using a one-dimensional, finite-difference model, based on the corresponding calculated heat fluxes. Values of h ranged from 700-5000 W/m 2 · K. The various coatings used, and the different levels of substrate roughness, contributed to the wide range of h values reported. The heat transfer coefficient was found to increase with initial superheat, thickness of strip and smoother coatings. Correlations were derived between peak heat fluxes and the most significant variables. More importantly, the transient evolution of q and h after their peak values were assessed and good correlations could be derived. The findings of this work are believed to be useful for industrial processes, since they give a better picture of the influence of some important variables on the heat transfer involved for this particular type of metal-substrate contact. This is relevant, for example, to horizontal direct strip casting processes currently under investigation for the production of low carbon steel strips.KEY WORDS: horizontal strip casting; aluminum alloys; single-belt caster; inverse heat conduction.processes, such as belt casters, relatively little data are available and even these have been obtained under diverse experimental conditions. Farouk et al. 2) performed measurements of heat fluxes between a belt and either liquid aluminum or steel. Their apparatus was motionless, nor was any relationship between heat fluxes and relevant variables proposed.Chen and co-workers 3) investigated some of the parameters involved in the interfacial heat transfer behavior in free-jet casting of Wood's alloy onto a moving substrate. The thicknesses of ribbons varied between 0.1 and 0.25 mm.A simulation of low-carbon steel strip casting was carried out by Couture et al. 4) They used a copper mold moving at very low speed for the substrate. Their work focussed on microstructural characterization.Strezov and Herbertson, 5) made a recent contribution to the subject, studying heat transfer characteristics between a...
Near‐net‐shape casting is one of the key technologies to improve process efficiency of steel production. Single‐belt strip casting is recognized as a promising technology for thin strip production because of the advantages like well‐controlled heat transfer rate, flexibility in production rate, compactness of equipment, and so on. In this study a newly designed simulator of the single‐belt strip casting process was developed. The simulator solidifies molten metal on the running solid metal bar with a groove for molten metal deposition pushed by a pneumatic cylinder. Capability of this simulator design was discussed by one‐dimensional numerical heat transfer analysis. It showed that a steel casting bar thicker than 40 mm was capable of casting test of 10 mm thick steel strip even if interfacial thermal resistance existed. Finally, the simulator was applied to the casting test of aluminum strip, and successfully estimated the variation of the interfacial heat flux from the solidifying strip to the casting bar.
A mathematical model was developed to simulate fluid flow/heat transfer phenomena in a proposed configuration for a single-belt caster. The main goal of the research was to evaluate the flow modifications yielded by the insertion of a flow modifier in the computational domain. This paper deals in particular with the influence of some empirical parameters in the model predictions.The most important inputs for the mathematical model were found to be the interfacial heat transfer coefficient h and the morphology constant C. These two parameters, in addition to the numerical treatment for turbulence, had a remarkable influence on the model's outputs. A very high value of C generates strong dampening of velocities within the interdendritic, mushy zone. This leads to predictions of premature solid shell growth within the extended metal delivery zone, leading to too thick a solid shell and too thin a mushy zone at the end of the computational domain. As for the instantaneous heat transfer coefficient, h, an attempt was made to predict its transient characteristics using an experimental simulator. This equipment mimics metal deposition on a substrate moving at the same velocity as an industrial belt (ϳ0.5-1 m/s). Comparisons of predictions made on the basis of different schemes for the variation in h are reported. The importance of an accurate prediction for the way h varies, in terms of the belt's required cooling length, is stressed.KEY WORDS: single-belt strip casting; heat flux measurements; flow through porous media.
Experimental apparatus simulating a horizontal belt caster has been constructed for the study of thin strip casting of steels and light metal alloys. In this apparatus, the solidifying metal is deposited onto a moving substrate. The substrate was flame sprayed with various commercial coatings while its speed and the thicknesses of strip produced matched industrial values. The main objective of the present work was to determine the influence of various operational variables on local cooling rates and final microstructures. To this end, experiments were carried out to study the effects of various types of coating, roughness of the substrate, initial superheat, and strip thickness on heat fluxes. An interesting feature of this equipment is that the strip is subjected to different rates of cooling at the lower and upper surfaces, allowing two different rates of solidification to be studied simultaneously.
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