| 摘要 |
PROBLEM TO BE SOLVED: To restrain the shift of carbon into molten steel from flux so as to be possible to restrain the carbon pick-up in the inner part and on the surface skin part of a cast slab by adding the specific quantity of S in the flux for extra-low carbon steel so as to accumulate S into the interface between the molten flow and the molten steel. SOLUTION: S in the flux is contained at 1-7 wt.%. S blended in the flux is supplied with a form of S-containing base particles, gypsum particles, sulfide particles, etc. Size of the S particles is desirable to be <=50μm. In the case the S content added in the flux is <=1%, C pick-up into the molten steel from the flux can not be restrained. On the other hand, in the case the S content is high, since the carbon concn. in the molten steel is stabilized to the low level, but reversely, S in the molten steel is increased, the upper limit of S is made to 7%. The flux can be used to the one containing 60-90% base particles and 10-40% adjusting particles as the same as the conventional one, but since S is naturally mixed from Portland cement as the blending raw material, the S content thereof becomes about 0.1-0.3%.
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