COLD-FINGER MEASUREMENT OF HEAT TRANSFER THROUGH SOLIDIFIED MOLD FLUX LAYERS

The thermal resistance between the cast strand and the copper mold in continuous casting is dominated by the conduction resistance through the partially solidified mold flux layer and the contact resistance between the solidified mold flux and the mold. In the cold-finger approach, a freeze layer of mold flux is grown on a water-cooled probe immersed in molten flux. In principle, the thickness of the solid layer and the steady-state heat flux can be used to estimate conductivity and contact resistance. Lower-basicity fluxes generally give somewhat lower heat fluxes under these conditions and result in formation of glassy films. Glassy films are generally significantly thinner than crystalline films, because of the higher thermal conductivity of crystalline films. A potential approach to estimate thermal conductivity and contact resistance from transient changes in solid film thickness and heat flux is outlined.