Patent ID: 6709535
Filing Date: 2004-03-23
Classification: C22C,Y10T

Abstract:
A superhigh-strength dual-phase sheet having a tensile strength of at least about 780 MPa of excellent fatigue characteristic in a spot welded joint containing a ferritic microstructure and a martensitic microstructure containing:C: 0.08-0.20% (mass% hereinafter), Si: 0.5% or less (inclusive of 0%) Mn: 3.0% or less (exclusive of 0%) P: 0.02% or less (inclusive of 0%) S: 0.02% or less (inclusive of 0%), and Al: 0.001-0.015%, which further contains Mo: 0.05-1.5%, and Cr: 0.05-1.5%, and satisfying: the average Vickers hardness of the ferritic microstructure of 150 Hv or more and the average Vickers hardness of the martensitic microstructure of 500 Hv or more.