Quality Improvement of Continuously Cast Stainless Steel Blooms through Electromagnetic Stirring

Abstract

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.
(4) A homogeneous distribution of δ-ferrite in SUS 304 blooms and a refinement of Ti (CN) clusters in SUS 321 blooms are obtained by the stirring.