The high intensity cold rolling steel sheet and its production manner null which are superior in deep drawing Characteristic and chemical conversion coating

摘要

PURPOSE: To provide a high strength cold rolled steel sheet having a balance of strength and workability exceedingly excellent compared to that of the conventional one and furthermore excellent in chemical convertibility. ;CONSTITUTION: This is a cold rolled steel sheet contg., as strengthening components, Si, Mn and P and contg. one or two kinds among B, Ti and Nb, and in which, as for the same Si, Mn and P, E value determined by the relationship of [%Si], [%Mn] and [%P] which are each content thereof satisfies the following inequality: [numerical inequality] E=6+2.5[%Si]+0.5[%Mn]+10.5[% P]≥7, the X-ray diffraction intensity ratio I of the intensity I₍₂₂₂₎ of the {222} plane parallel to the sheet plane in the central face of the sheet thickness to the intensity I₍₂₀₀₎ of the {200} plane parallel to the sheet plane satisfies I×E≥240 in the relationship with the same E value and the difference (ΔC) between the average carbon concn. of the layer to 100μm in the thickness direction from the surface of at least either steel sheet and the average carbon concn. on the inside in the thickness direction therefrom is regulated to ≥20% of the average carbon concn. in the total thickness.;COPYRIGHT: (C)1995,JPO