Patent ID: 9708684
Date: 2017-07-18
CPC Classifications: B32B,C21D,C22C,C23C,Y10T

Claim:
1. A hot-dip galvanized steel sheet in which a hot-dip galvanized layer is formed on a surface of a base steel sheet, the hot-dip galvanized steel sheet having excellent elongation properties, wherein the base steel sheet: contains 0.02-0.08% of carbon (C), 1.3-2.1% of manganese (Mn), 0.3% or less of silicon (Si) (excluding 0%), 1.0% or less of chromium (Cr) (excluding 0%), 0.1% or less of phosphorous (P) (excluding 0%), 0.01% or less of sulfur (S) (excluding 0%), 0.01% or less of nitrogen (N) (excluding 0%), 0.02-0.06% of aluminum (sol. Al), 0.2% or less of molybdenum (Mo) (excluding 0%), 0.003% or less of boron (B) (excluding 0%), and a remainder of Fe and other inevitable impurities, in wt %; has a microstructure including 90% or more of ferrite, and a remainder of martensite and bainite, wherein B (%), as defined by Equation 1, is 3% or less; contains a percentage of martensite (M %) having an average particle diameter of 5 μm or less occupying space in ferrite grain boundaries (including grain boundary triple points) of 90% or higher, as defined by Equation 2; and at ¼t based on the thickness (t) of the sheet, the ratio of a C concentration (a) in the ferrite phase to a C concentration (b) in the martensite phase, i.e., (a)/(b), is 0.7 or less, and the ratio of an Mn concentration (c) in the ferrite phase to an Mn concentration (d) in the martensite phase, i.e., (c)/(d), is 0.8 or less, where BA is the area occupied by bainite, and MA is the area occupied by martensite, where M