Abstract: In a steel mill operation, continuous casting of steel is accomplished by means of a vertically reciprocating mold that forms a billet or slab which progressively moved downward beneath the mold. A plurality of expansible metal shoes are provided, each of which can be selectively contracted for tightly squeezing the casting. The shoes are placed in sequentially spaced positions beneath the mold so that the casting passes through them. The shoes are selectively expanded and contracted, and are moved vertically, in conjunction with the reciprocating movement of the mold, in such manner as to mechanically support the casting and at the same time provide a longitudinal driving force for withdrawing it from the mold. Cooling liquid is continuously supplied to the shoes in order to withdraw heat from the molten metal in the interior of the casting. Whenever each shoe is contracted the resulting surface contact pressure against the casting results in an increased rate of withdrawal of heat.