スラブ状小鋳片の中心偏析に及ぼすバルジングの影響

抄録

The influence of the bulging on the formation of the centerline segregation in continuously cast slabs (CC slabs) was investigated with the following experimental method. Experimental continuously cast slabs (experimental CC slabs) with a section of 130 mm×400 mm were cast continuously to the length of 2.5 m and bulged during solidification by compressed nitrogen gas from the meniscus under various conditions.
The results obtained are summarized as follows.
(1) The centerline segregation of the experimental CC slabs without bulging is very slight.
(2) The degree of the centerline segregation is significantly influenced by the bulging conditions.
(a) The centerline segregation, nearly equal to that of the regular CC slabs, is generated by the bulging of 45 mm at the final stage of the solidification, where only the mashy zone remains, even if the experimental CC slab is bulged once.
(b) The remarkable centerline segregation is not recognized even if the bulging of 46 mm is repeated when the enough residual liquid remains.
(c) Even if the equiaxed zone is thick, the centerline segregation is generated remarkably in the case of the condition as in (a) above.
(3) The centerline segregation, nearly equal to that of the regular CC slabs, is the result of the accumulation of the enriched interdendritic liquid with the solid fraction from zero to 0.5. The accumulation is generated by the absorption effect formed by bulging at the final stage of the soldification where only the mashy zone remains.