Modeling transient slag-layer phenomena in the shell/mold gap in continuous casting of steel |
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Authors: | Ya Meng Brian G Thomas |
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Affiliation: | (1) Department of Mechanical and Industrial Engineering, the University of Illinois at Urbana-Champaign, 61801 Urbana, IL |
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Abstract: | Mold-slag friction and fracture may cause heat-transfer variations in continuous casting, which leads to steel shell temperature
and stress variations, resulting in surface cracks. Analytical transient models of liquid slag flow and solid slag stress
have been coupled with a finite-difference model of heat transfer in the mold, gap, and steel shell to predict transient shear
stress, friction, slip, and fracture of the slag layers. The models are validated by comparing with numerical models and plant
measurements of mold friction. Using reported slag-fracture strength and time-temperature-transformation (TTT) diagrams, the
models are applied to study the effect of casting speed and mold-powder viscosity properties on slag-layer behavior between
the oscillating mold wall and the solidifying steel shell. The study finds that liquid-slag lubrication would produce negligible
stresses. A lower mold-slag consumption rate leads to high solid friction and results in solid-slag-layer fracture and movement
below a critical value. Crystalline slag tends to fracture near the meniscus and glassy slag tends to fracture near the mold
exit. A medium casting speed may be the safest to avoid slag fracture, due to its having the lowest critical lubrication consumption
rate. The high measured friction force in operating casters could be due to three sources: an intermittent moving solid slag
layer, excessive mold taper, or mold misalignment.
Other symbols are defined in Table I |
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