Patent ID: 6612364
Filing Date: 2003-09-02
Classification: B22D

Abstract:
A method of casting a continuous slab with reduced segregation and core porosity, said method comprising the steps of:(a) continuously casting a molten metal into a continuous casting mold and solidifying a shell of said metal around a liquid core in a solidifying strand emerging downwardly from said mold at a certain thickness; (b) passing the solidifying strand through a succession of strand guide segments each consisting of two groups of multiple guide rollers on opposite sides of the strand and flanking the strand to define a width of a path of the strand between the groups and thereby control a thickness of the strand between the respective groups of rollers; (c) in a first strand guiding stage immediately downstream of said mold guiding said strand in a parallel stretch through at least one of said strand guide segments with a certain slab thickness; (d) spaced downstream of said first strand guiding stage and in a soft reduction stage with convergence in at least one of said strand guide segments compressing said strand at least partially to a finished slab thickness and with said soft reduction stage extending at least to a liquidus point between said liquid core and full solidity of the strand; (e) upstream of said soft reduction stage and downstream of said first strand guiding stage, in a second strand guiding stage and between converging strand guides of at least one of said strand guide segments over a region in which said core of said strand remains liquid, effecting liquid-core reduction of said strand to a thickness less than said certain thickness; and (f) upstream of said soft reduction stage and in a third strand guiding stage and between diverging strand guides of at least one of said strand guide segments over a region in which said core of said strand remains liquid, effecting ferrostatic liquid-core expansion of said strand to a thickness greater than said certain thickness and greater than the thickness of said strand upon said liquid-core reduction, thereby forming a bulge, said strand subsequent to said ferristatic liquid-core expansion being subjected to said soft-reduction stage whereby said bulge is pressed in.