High-strength hot dip galvanized steel sheet having excellent plating quality, plating steel sheet, and manufacturing methods therefor

A steel sheet comprising, by weight %:

• 1.0 to 8.0% of Mn, 0.05 to 3% of Si, 0.06 to 0.4% of C, 0.005 to 3.0% of Al, 0.04% or less of P, 0.015% or less of S, 0.01% or less of N, 1.5% or less of Cr, 0.005% or less of B, with a balance of Fe and inevitable impurities,
• wherein each of a GDS profile of an Mn element and a GDS profile of an Si element, observed from a surface thereof in a depth direction, sequentially includes a maximum point and a minimum point,
• a difference between a value obtained by dividing a Mn concentration at the maximum point in the GDS profile of the Mn element by a Mn concentration of a base material and a value obtained by dividing a Mn concentration at the minimum point in the GDS profile of the Mn element by the Mn concentration of the base material (a difference of converted concentration of Mn) is 10% or more, and
• a difference between a value obtained by dividing a Si concentration at the maximum point in the GDS profile of the Si element by a Si concentration of a base material and a value obtained by dividing a Si concentration at the minimum point in the GDS profile of the Si element by the Si concentration of the base material (a difference of converted concentration of Si) is 10% or more,
• wherein when no minimum points appear within 5 μm of depth, a point at a depth of 5 μm is considered to be a point at which the minimum point appears.

A method for manufacturing a steel sheet, comprising:

• preparing a base steel sheet including, by weight %:
• 1.0 to 8.0% of Mn, 0.05 to 3% of Si, 0.06 to 0.4% of C, 0.005 to 3.0% of Al, 0.04% or less of P, 0.015% or less of S, 0.01% or less of N, 1.5% or less of Cr, 0.005% or less of B, with a balance of Fe and inevitable impurities;
• performing electroplating on the base steel sheet with an electroplating solution to form an Fe plating layer including 5 to 50 wt % of oxygen;
• and
• annealing the base steel sheet on which the Fe plating layer is formed by maintaining at a temperature range of 600 to 950° C. for 5 to 120 seconds in an annealing furnace with 1 to 70% H2-remaining N2 gas atmosphere, controlled at a dew point temperature of lower than −20° C.