| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high strength galvanized steel sheet excellent in the plated adhesion and the balance between the strength and the elongation even in the case of containing large amounts of Si and Mn. SOLUTION: To the steel sheet having composition containing 0.05-0.25 mass% C, 0.50-2.0 mass% Si, 1.0-3.5 mass% Mn, 0.01-1.0 mass% Al and a ratio of Mn to Si is≥0.5, a primary heating treatment is applied so that a ratio of an infrared absorbing spectrum intensity I(SiO<SB>2</SB>) of amorphous SiO<SB>2</SB>and an infrared absorbing spectrum intensity I((Fe,Mn)<SB>2</SB>)SiO<SB>4</SB>) of (Fe,Mn)<SB>2</SB>SiO<SB>4</SB>generated on the steel sheet surface after heating measured with a reflection type IR spectrum measuring instrument in an atmosphere at dew point -50°C to +40°C becomes≤0.3, and successively, a secondary heating treatment is applied in the temperature range of not lower than Ac<SB>1</SB>transformation point and not higher than Ac<SB>3</SB>transformation point after pickling so that the reduced amount with the pickling becomes 0.05-5 g/m<SP>2</SP>Fe conversion and thereafter, the galvanizing treatment is applied and if necessary, an alloying treatment is applied. COPYRIGHT: (C)2004,JPO
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