The strain age hardening die steel sheet and its production mannered null mass which are superior in normal temperature

摘要

PROBLEM TO BE SOLVED: To provide a strain age hardening type steel sheet having a high BH (Bake Hardenability) of ≥50 MPa and also excellent in cold non-aging properties, and to provide its production method.;SOLUTION: The strain age hardening type steel sheet excellent in cold non-aging properties has a composition comprising, by mass, ≤0.004% C, ≤0.6% Si, ≤2.0% Mn, ≤0.1% P, ≤0.0018% S, ≤0.01% Al, 0.3 to 2.0% Cr and 0.002 to 0.010% N, and in which the content of solid solution N is 0.002 to 0.007%, and the balance Fe with inevitable impurities. The density of sulfides with a grain size of ≥0.01 [μm] in the steel is ≤0.2 [pieces/μm²] per unit area, and further, the crystal grain size of ferrite is ≥5 μm.;COPYRIGHT: (C)2005,JPO&NCIPI