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B illet continuous casting machine with in-line reduction, was illstalled at K ishiwada Steel Co. , L td. , alld has been ill operation since March 1972. T his /Japer deals with various qualities of billets produced by this machine du ring the start up period. The followings have been found: (1) Center shrinkage cavities and porosities were well cured by the illline reduction process. (2) The non-metallic inclusions were elongated into the drawing direction throughout a billet by the in-line reduction process, however the inclusions locating at central /Jarts extended furthe!' than those at outer layers. (3) Microscop ic examinations yielded that as-cast billets consist of normal WidmannstiiUen structures bu t the in-line reduction im/JTOves the structure to some extent. (4) Difference of the tensile /Jroperties between the central /)art and the outer layer of billet was negligible. Consequently it is concluded that the in-line reduction process results in excellent qualities and soundness to billets.

Relation between holding time and maximum inclusion size of each position.

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