| 摘要 |
A hot dipped galvanized steel sheet with an excellent hole expansibility, a hot dipped galvannealed steel sheet, and a manufacturing method therefor are provided. The present invention relates to a hot dipped galvanized steel sheet having excellent hole expansibility and comprising a hot dipped galvanized layer formed on the surface of a base steel sheet, wherein the base steel sheet is composed of 0.02-0.08 wt% of carbon (C), 1.3-2.1 wt% of manganese (Mn), 0.3 wt% or less of silicon (Si) (excluding 0 wt%), 1.0 wt% or less of chromium (Cr) (excluding 0 wt%), 0.1 wt% or less of phosphorus (P) (excluding 0 wt%), 0.01 wt% or less of sulfur (S) (excluding 0 wt%), 0.01 wt% or less of nitrogen (N) (excluding 0 wt%), 0.02-0.06 wt% of aluminum (sol. Al), 0.2 wt% or less of molybdenum (Mo) (excluding 0 wt%), 0.003 wt% or less of boron (B) (excluding 0 wt%), and the balance of Fe and other inevitable impurities, the microstructure of the base steel sheet is composed of 90% or more of ferrite, the balance of martensite, and 3% or less of bainite defined by relation 1 according to area percentage, and the ratio (a/b) of the concentration (a) of C+Mn in the base structure within 10 μm, on average, on a surface layer of the base steel sheet and the concentration (b) of C+Mn in the base structure at the 1/4t point of the thickness of the base steel sheet is 0.7 or less. |
