Posco

Hyo Jung Kwak

Young-Ha Kim

Seok Jong Seo

The present invention relates to a hot-rolled steel sheet for a high strength galvanized steel sheet, having excellent surface quality, and a method for producing the same, the hotrolled steel sheet comprising, by weight %: C: 0.08 to 0.2%, Si: 0.03 to 0.15%, Mn: 1.4 to 2%, P: 0.001 to 0.05%, S: 0.001 to 0.03%, Al: 0.002 to 0.05%, and the remainder being Fe and unavoidable impurities. The weight ratio of Mn/Si is 20 to 30, the weight ratio of C/Si is 1 to 5, and the weight ratio of Si/P is 3 to 10. The hot-rolled steel sheet has a microstructure consisting of, in area fraction, 10 to 40% of bainite, 20 to 30% of pearlite and 40 to 60% of ferrite, and includes a ternary eutectic compound of FeO, FeSiOand Fe(PO)formed within 50 &#x3bc;m from the surface.

Hot-rolled steel sheet for high strength galvanized steel sheet, having excellent surface quality, and method for producing same

The present invention relates to a hot-rolled steel sheet for a high strength galvanized steel sheet, having excellent surface quality, and a method for producing the same, the hot-rolled steel sheet comprising, by weight %: C: 0.05 to 0.15%, Si: 0.03 to 0.10%, Mn: 0.7 to 1.39%, P: 0.001 to 0.05%, S: 0.001 to 0.03%, Al: 0.002 to 0.035%, and the remainder being Fe and unavoidable impurities. The weight ratio of Mn/Si is 15 to 25, the weight ratio of C/Si is 1 to 5, and the weight ratio of Si/P is 3 to 10. The hot-rolled steel sheet has a microstructure consisting of, in area fraction, 10 to 40% of bainite, 20 to 30% of pearlite and 40 to 60% of ferrite, and includes a ternary eutectic compound of FeO, FeSiOand Fe(PO)formed within 50 &#x3bc;m from the surface.

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Gwangyang-si, South Korea

Hyo Jung Kwak