Effect of Electromagnetic Stirring at the Final Stage of Solidification of Continuously Cast Strand

Abstract

It is commonly observed that severe V-channel segregates are associated with the equiaxed zone in the central region of a strand. This type of segregation may deteriorate the product qualities especially for sour gas service. The modification of V-segregates is found to be attained by electromagnetic stirring at the final stage of solidification. The laboratory scale stirring experiments have been carried out in order to eliminate V-segregation and the following results have been obtained.
1) V-segregation streaks can be eliminated by linear or rotary type stirrer at the final stage of solidification.
2) The upward flow of molten steel at the solidification front which may prevent the inter-dendritic liquid flow toward the bottom is effective.
3) In the case of stirring by rotary type stirrer, adequate amount of fine equiaxed crystals is necessary. Alternating stirring at the final stage of solidification may prevent coagulation of equiaxed crystals and modify the packing of them.
4) It was found that only weak stirring is enough.
5) It is important to time the stirring to the progress of solidification. Optimum stirring period should be aimed at right after the precipitation of crystals, fraction of solid equals to 0.1 at the center of a strand.