| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for continuously casting a P-containing steel by which a streak defect, especially white streak defect caused after plating/galvannealing can stably be prevented in a galvannealed steel sheet. SOLUTION: In the method for finally producing the galvannealed steel sheet by continuously casting a steel containing≥0.035% P. a critical value IQcr causing the white streak defect is obtained from a relation V<SP>0.8</SP>ΔTm and the occurrence of the white linear streak defect, and then the steel is continuously cast under condition that the V<SP>0.8</SP>ΔTm is more than the critical value IQcr. Wherein, V is an average flowing speed (cm/s) of molten steel till a prescribed position in a mold, andΔTm is an over-heating degree (°C) of molten steel at the prescribed position in the mold, and the prescribed position in the mold is the position of 30 mm depth from a meniscus part at 1/4 width direction and 1/2 position in the thickness direction from the edge part of the mold. COPYRIGHT: (C)2009,JPO&INPIT
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