MATHEMATICAL AND PHYSICAL MODELING OF STEEL FLOW AND SOLIDIFICATION IN TWIN-ROLL HORIZONTAL BELT THIN-STRIP CASTING MACHINES/

Near-net-shape casting technology is one of the most important researc h areas in the iron and steel industry today. Driving forces for the d evelopment of this technology include a reduction in the number of ope rations needed for conventionally produced strip. This is especially t rue of hot rolling operations. The consequent reduction in investment cost when considering new industrial facilities, makes near-net-shape casting operations extremely attractive from a commercial standpoint. Various processes for near-net-shape casting of steel are currently be ing developed around the world. Of these processes, twin-roll casting machines represent a major area of concentration. We believe that one of the main issues concerning the design of twin-roll casters is the m etal delivery system and its effect on the homogeneity of solid shell formation, segregation and surface quality. In the present work, compu tational fluid dynamics has been used to study different metal deliver y systems for twin-roll casting (TRC) and horizontal belt casting (HBC ) operations. The METFLO code has been adapted to simulate three-dimen sional turbulent fluid flows, heat transfer and solidification in thes e types of machines. The enthalpy-porosity technique was used to coupl e fluid flow and solidification phenomena. Two configurations for meta l delivery system have been studied to date for TRC: one is a conventi onal tubular nozzle with horizontal outlets in the directions of the s ide dams; the other is a slot nozzle with a vertical inlet stream. The se simulations have been applied to a pilot easter bring studied in Ca nada, with a roll radius of 0.30 m, producing steel strips with thickn esses ranging from 4 to 7 mm, at relatively low roll speeds ranging be tween 4 and 12 m/min. Different positions and penetrations of the nozz les in the liquid pool have also been analysed. It has been shown that a tubular nozzle leads to the formation of a non-uniform solid shell along the roll width. In both configurations, a thicker solid shell is formed close to the roll edges, due to the presence of the side dams. In the case of HBC, computations have been made for an extended nozzl e metal delivery system, and preliminary water modelling tests carried out to confirm the flow delivery concepts proposed. In addition, inst antaneous heat flux measurements to simulated belt substrates have bee n performed for the horizontal casting of aluminum strip that show som ewhat similar characteristics to those measured for steel in the pilot TRC, in terms of transient peaks and decays. (C) 1998 Published by El sevier Science Inc. All rights reserved.