HIGH-STRENGTH COLD ROLLED STEEL SHEET HAVING HIGH HOLE EXPANSION RATIO, HIGHSTRENGTH HOT-DIP GALVANIZED STEEL SHEET, AND MANUFACTURING METHODS THEREFOR

摘要

Provided is a high-strength cold rolled steel sheet, a high-strength hot-dip galvanized steel sheet manufactured using the cold rolled steel sheet, and manufacturing methods therefor, the high-strength cold rolled steel sheet comprising, by wt %, 0.17-0.21% of carbon (C), 0.3-0.8% of silicon (Si), 2.7-3.3% of manganese (Mn), 0.3-0.7% of chromium (Cr), 0.01-0.3% of aluminum (Al), 0.01-0.03% of titanium (Ti), 0.001-0.003% of boron (B), 0.04% or less of phosphorus (P), 0.02% or less of sulfur (S), 0.01% or less of nitrogen (N) and the balance of iron (Fe) and other inevitable impurities, wherein the amounts of carbon (C), silicon (Si) and aluminum (Al) satisfy the following mathematical relation (1). [Mathematical relation (1)] [C]+([Si]+[Al])/5≤0.35% (wherein [C], [Si] and [Al] respectively mean the wt % of C, Si and Al.)