Jfe Steel Corporation

Hideya Masaki

Naoki Kikuchi

Yusuke Fujii

Yoshie Nakai

Kenji Tsuzumi

A mold powder which prevents surface defects from occurring on a surface of a cast slab of Al-containing hypo-peritectic steel having Al: 0.2% to 2.0%, by mass %, and, in a hypo-peritectic region, C: 0.08% to 0.17%, by mass %. The mold powder includes CaO, SiO, NaO, LiO, F, and C. LiO/NaO is 0.6 or more, 1.0+0.05×Al≤CaO/SiO≤2.0−0.35×Al, 10<LiO+0.5×NaO+0.8×F<20, and 1.00≤F/(LiO+0.5×NaO+1.46)≤1.24 are satisfied where Al is content by mass % of molten steel, and respective contents of the remaining elements are by mass %. A viscosity of the mold powder at 1,300° C. is in a range of 0.05 Pa·s to 0.20 Pa·s, and a crystallization temperature of the mold powder is in a range of 1,100° C. to 1,250° C.

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Tokyo, Japan

Hideya Masaki