Study on Solidifying Shell Growth Behavior in a Large Section Bloom Casting Mold employing CON1D

Abstract

Large section bloom caster (700x700mm2) has extremely low casting speeds (0.05~0.1mpm). There are many factors to improve the surface quality in bloom casting of steel, but one of the important factors is the solidifying shell growth behavior. Which is effected by solid mold flux layer, liquid mold flux layer, air gap, oscillation marks and contact resistance. Air gap, one of the factors to give an effect on shell growth behavior, can be adjusted by mold taper. Mold taper compensates for the strand shrinkage to maintain good contact between mold and solidifying shell. In case insufficient mold taper applied, air gap occur between mold hot-face and shell surface. Air gap works as a thermal resistance layer, which interrupts the heat transfer and shell growth. In case solidifying shell thickness is thin, solidifying shell can be torn or occur the bulging by ferro-static pressure. In this article, calculations of shell growth and heat transfer are approached with a simple, but comprehensive computational model of heat transfer and solidification in casting process called CON1D. Prediction of mold taper is additionally proceeded with shrinkage profile derived from CON1D calculation along casting direction.