| 摘要 |
PURPOSE:To prevent material deterioration due to natural aging by specifying the amount of C, Mn, P, and N in a cold rolled steel plate and utilizing the synergistic action of Mn and P affecting N aging. CONSTITUTION:A cold rolled steel plate consists of C: 0.002-0.12wt%, soluble Mn (total Mn%-55/16O%-55/32S%):0.35-2.0wt%, P: 0.040-0.15wt%, and the effective N quantity (NE%) represented by NE%=total N%-14/27solAl%- B% is specified to 0.0003wt%<=NE<=NM if NM<=0.0040wt%, and to 0.0003wt%<= NE<=0.0040wt% if NM>0.0040wt%, where NM=[0.00035 exp 2.8X(solution Mnwt%)+6.9X(Pwt%)]. The steel plate of such composition is subjected to recrystallization softening annealing and thermally refined rolling. The steel is then given a cold process strain of 0.5% or more and heated to 120-300 deg.C thereby providing bake hardening by artificial aging. The process provides a steel plate having an excellent cold forming property and bake hardening property. |
