| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high strength thin steel sheet which has excellent hole expansibility and local ductility using a mixed structure of precipitation hardened ferrite and bainite, and a method for producing the same. <P>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 made of a ferrite phase and a bainite phase, cooling after hot rolling is controlled to regulate the spacing of the precipitated faces of interphase boundary precipitation in the region of ≥40% of the ferrite phase to 20 to 60 nm, and the carbon nitrides of Ti and Nb are precipitated into the ferrite phase by the interphase boundary precipitation, thus the ferrite is subject to precipitation hardening. <P>COPYRIGHT: (C)2012,JPO&INPIT |
