Abstract: An adequate mold taper design must consider both mold thermal distortion and solidified shell shrinkage. The optimal mold should adapt fully the solidified shell shrinkage, and allow the sufficient contact between solidified shell and mold without causing excessive mold-shell interference. Considering the shrinkage characteristic of solidified shell in the billet and round mold, the design and calculation formula about the opti-mal longitudinal profile curve and the optimal taper curve of the billet and round mold for high speed continuous casting are obtained. It clearly embodies the effects of solidified shell shrinkage, steel grade, cooling condition and casting speed. The optimal longitudinal profile curve consists of the beeline from the intake of mold to the site close to metal level and the curve under the beeline, which are tangent each other, making the taper changing continuously and avoiding the effect of the fluctuation of metal level. Close to metal level, the optimal longitudinal profile curve is very approximate to a parabola. The mold with size of 154.5 mm×152.5 mm, is designed for one Iron and Steel Co. Ltd.. The maximal casting speed of the mold is 3.1 m/min, which exceeds the desired value of 2.7 m/min.

Key words: Billet and round mold, Calculation, Design, Optimal longitudinal profile curves, Optimal taper curves