| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot dip galvannealed steel sheet excellent in ductility, in which the base material is excellent in local ductility, and plating wettability and powdering properties are improved and to provide its production method. SOLUTION: This steel sheet has a composition containing, by mass, 0.05 to 0.2% C, 0.02 to 0.70% Si, 0.5 to 3.0% Mn, 0.005 to 0.10% P, <=0.1% S, 0.10 to 2.0% Al and <=0.01% N, also satisfying Si(%)+Al(%)>=0.5, and the balance Fe with inevitable impurities, the base material contains an austenitic phase of >=1% by volume, further, in the plating film, the concentration of Fe is 8 to 15 mass%, also, the averageΓphase thickness in the plating film is <=2μm, the maximumΓ1 phase length in the thickness direction is <=1.5μm, and the relation of the maximumΓ1 phase length/theΓphase thickness <=1.0 is satisfied.
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