Boiling Curve Approach for Thermal Boundary Conditions in DC Casting

Summary

A relation for the heat flux or heat transfer coefficient in the secondary cooling zone in DC Casting is necessary to be able to describe the cooling conditions close to the surface of a billet or slab. A time averaged heat transfer coefficient is normally good enough for describing the thermal behavior in the center region. Because surface thermal history is very important for the quality of the cast product, a relation for the heat flux as a function of process parameters needs to be found. Unfortunately literature does not give the answer in this case. No good theoretical framework exists for establishing thermal boundary conditions in convection and water boiling mixed cooling regime. The best description on this subject can be found in Weckman and Niessen (1). Mr. Jensen from Elkem has derived key values to produce two boiling curves, one for the impingement region and one for the down streaming water region, which in combination produce (almost) the same heat transfer values as a function of distance from the impingement point as those measured (2). In the current research Mr. Jensen's approach was extended to get better resemblance with experiments.