High-strength hot-dip galvanized steel sheet with excellent spot weldability and stability of material properties

摘要

A high-strength hot-dip galvanized steel sheet is provided which comprises a composite structure consisting essentially of ferrite and martensite. The steel comprises, by mass %, C: 0.05 to 0.12 %, Si: not more than 0.05 %, Mn: 2.7 to 3.5 %, Cr: 0.2 to 0.5 %, Mo: 0.2 to 0.5 %, Al: not more than 0.10 %, P: not more than 0.03 %, and S: not more than 0.03 %. The high-strength hot-dip galvanized steel sheet has not only excellent spot weldability, but also excellent "stability of material properties", including tensile strength, total elongation, and yield strength, in a high range of strengths from 780 to 1180 MPa, even if the manufacturing condition (especially, the condition of the cooling process after annealing the steel sheet) is changed.