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 equi-axed crystal zone in the central region of a continuously cast strand. This type of segregation may deteriorate the qualities of products especially for sour gas service. The modification of V-segregates is found to be attained by electromagnetic stirring at the final stage of solidification of casts.
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 stirring at the final stage of solidification with either linear or rotary type stirrer.
(2) The upward flow of molten steel at the solidification front induced by the linear type stirrer may prevent the interdendritic liquid flow toward the bottom which leads to the formation of V-segregates.
(3) The presence of adequate amount of fine equi-axed crystals at the final stage of solidification is the essential condition for the elimination of V-segregates by the rotary type stirrer. Alternating stirring direction around the cast axis is preferred for the prevention of coagulation of equiaxed crystals and results in the modification of packing of them.
(4) In addition to the above results, the timing and intensity of stirring with which the best result can be obtained have been discussed.