POSCO Holdings Inc.
High-strength hot-dip galvanized steel sheet having excellent surface quality and spot weldability

Abstract:

Provided is a high-strength hot-dip galvanized steel sheet having good surface quality and spot weldability. The high-strength hot-dip galvanized steel sheet includes a base steel sheet and a zinc plating layer formed on the base steel sheet. The base steel sheet includes carbon (C): 0.1% to 0.3%, silicon (Si): 0.5% to 2.5%, manganese (Mn): 2.0% to 8.0%, soluble aluminum (sol.Al): 0.001% to 0.5%, phosphorus (P): 0.04% or less (excluding 0%), sulfur (S): 0.015% or less, nitrogen (N): 0.02% or less, chromium (Cr): 0.01% to 0.7%, titanium (Ti): (48/14)*[N] % to 0.1%, and a balance of iron (Fe) and inevitable impurities. The base steel sheet has a microstructure comprising ferrite in an area fraction of 5% to 30%, austenite in an area fraction of 5% to 20%, bainite and martensite in an area fraction of 50% to 80%, and precipitates in an area fraction of 2% or less.