The high intensity which is superior in fatigue property and local ductility the black sheet and its production mannered

摘要

PROBLEM TO BE SOLVED: To provide a high strength thin steel sheet which has excellent fatigue properties and local ductility using a mixed structure of precipitation strengthened ferrite and martensite, and a method for producing the same.;SOLUTION: Nb of 0.01 to 0.10% and Ti of 0.01 to 0.20% are incorporated into a steel, the structure of the steel is made of the one composed of a ferrite phase and a martensite phase, cooling after hot rolling is controlled to regulate the spacing of the precipitated faces of interface boundary precipitation in the region of ≥40% of the ferrite phase to 20 to 60 nm, and the carbonitrides of Ti and Nb are precipitated into the ferrite phase by the interphase boundary precipitation, thus the ferrite is subject to precipitation hardening.;COPYRIGHT: (C)2012,JPO&INPIT