| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength hot dip galvanized steel sheet and a high-strength galvannealed steel sheet having excellent plating peeling resistance upon high working using a high Si-containing steel sheet as a base material, and to provide a method for producing the hot dip galvanized steel sheet and the galvannealed steel sheet in a CGL (continuous galvanizing line) provided with an all radiant tube type heating furnace in an annealing furnace. SOLUTION: The surface of a steel sheet comprising, as the chemical components of a steel, by mass, 0.01 to 0.15% C, 0.8 to 1.8% Si, 1.8 to 2.7% Mn, 0.01 to 0.1% Al, 0.005 to 0.025% P and ≤0.01% S, and the balance Fe with inevitable impurities is provided with a galvanizing layer in which plating weight per side is 20 to 120 g/m<SP>2</SP>, in the surface layer part of the steel sheet directly below the galvanizing layer, amorphous SiO<SB>2</SB>grows so as to be a dendrite shape from the grain boundaries toward the insides of ferrite grains in a region from directly below the galvanizing layer to 2 μm, and also, crystalline Si, Mn based composite oxides are precipitated into substrate iron grains within 1 μm from the grain boundaries in the region from directly below the galvanizing layer to 10 μm. COPYRIGHT: (C)2010,JPO&INPIT
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