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 f ollowing 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.

Effect of the Gap Between Copper Mold and Solidified Shell on the Fluid Flow in the Continuous Casting Strand with Mold Electromagnetic Stirring

“…The benefits of M‐EMS were widely recognized by metallurgists and industries: enlarging the equiaxed crystal zone, reducing center segregation and porosity, intensifying the fluid flow, heat, and mass transfer near the meniscus, helping the removal of inclusions from the molten steel. Many studies investigated the effect of M‐EMS on the inner quality of continuous casting (CC) blooms including center segregation, center porosity, and equiaxed crystal ratio by industrial trials. In the past decades, the effect of M‐EMS on fluid flow, temperature distribution, species transfer, and removal of inclusions was numerically simulated .…”

Simple model of microsegregation during solidification of steels

“…Voller and Beckermann [8] showed that, that his model agreed better with the experimental data of across a wide range of cooling conditions, this model is able Matsumiya et al [17] than did predictions using Eq. [4]. Howto match full coarsening model results by simply adopting ever, Voller et al [8] pointed out that the performance of a constant value of ␣ C ϭ 0.…”

“…where C L,i is the liquid concentration of a given solute eleTo satisfy this requirement, Ohnaka [33] presented a simple ment at the solid-liquid interface, C 0,i is the initial liquid modification of ␤ i to replace Eq. [4]. It is based on compariconcentration, k i is the equilibrium partition coefficient for son with approximate solutions of the diffusion equation for that element, and f S is the solid fraction.…”

“…[1,2,3] Macrosegregation is also affected to the grain size, and (c) the cooling conditions, which by nozzles, which direct the liquid; electromagnetic forces, depend on macroscopic heat conduction in the casting. which enhance mixing; [4,5,6] and by thermal or mechanical (3) Linking of the microsegregation phenomena with the bulging or deformation of the casting during solidification. [7] fluid flow and associated macrosegregation.…”

Effect of Mold Electromagnetic Stirring and Final Electromagnetic Stirring on the Solidification Structure and Macrosegregation in Bloom Continuous Casting

“…[7][8][9] In the final solidification zone, final electromagnetic stirring (F-EMS) was utilized to optimize the porosity and macrosegregation in the center of the billet or bloom. [10][11][12] For the 260 mm  300 mm bloom continuous caster of bearing steel, Yang et al [13] found that the center segregation of carbon decreased with the increasing current intensity of M-EMS. When 300 A of current intensity was applied, the center carbon segregation index of the bloom was 1.04 and the carbon segregation index in the cross section of the bloom was within the range of 0.95-1.05.…”