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Synopsis:Electromagnetic stirring was applied in order to improve the qualities of continuously cast stainless steel blooms for seamless tubes.The results are summerized as follows:(1) Grain refinement of cast structure of blooms is obtained by the stirring. The tendency to the equiaxed crystals grow is stronger in the order SUS 316, SUS 321, SUS 304 and SUS 430.(2) White bands, negative segregation bands of solutes, in stirred blooms are formed. Negative segregation of solutes at the white band increases its intensity in proportion to equilibrium partition coefficient of solutes.(3) Center cavities in blooms are converted into dispersed pourous form from pipe form and the star cracks disappear by the stirring.

SynopsisElectromaglletic stirring was ajJjJiied 10 improve the qualities oj conlilll/ousty cast stainless steel blooms Jor seamless tubes. II has beell showlI Ihat (I) Grain refinem ent oj cast struclure qj blooms is obtailled by the stirring. Th e tendency Jar equiaxed crystals to grow becomes jJrolloUlI.ced ill the ascending order oj SUS316, S US 321. S US304 and S US4 30. (2) White bands, negative segregation bands oj solutes, are Jormed ill the stirred blooms. N egative segregation oj solutes at the white band illcreases its intensity in proportion to equilibrium partition co'!/Jiciellt oj solutes. (3) Center cavities in blooms are cOllver ted illto disjJersed porolls Jorm Jrom jJipe Jorm and the star cracks disappear by the stirring. (4) A homogeneous distribution oj o:ferrite in SCS304 blooms alld a refillement oJ Ti (CN) clusters ill Sr..;S321 bloOlllJ are obtained by the stirrillg.

Effects of electromagnetic stirring on the solidification structure of continuously cast SUS430 slabs were investigated to reduce the ridging of cold-rolled sheets by grain refinement of the solidification structure. The following results were obtained: (1) The area in which equiaxed crystals form increases with increasing stirring intensity and decreasing superheat (4T) of molten steel. The most suitable stirring mode is the alternate stirring. The effect of 4T can be moderated by lowering the position of the stirrer, but the ratio of equiaxed crystals decreases in this case. Appropriate conditions for obtaining a ratio of equiaxed crystals over 60% were determined. (2) Ridging is reduced as the ratio of equiaxed crystals increases. Stable ridging obtained for 50% or more equiaxed crystals is the same as that of steel sheets rolled from ingots.

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