HIGH TENSILE STRENGTH COLD ROLLED STEEL SHEET HAVING HIGH CORROSION RESISTANCE AND HIGH WORKABILITY AND EXCELLENT IN ELONGATION FLANGING PROPERTY AND ITS PRODUCTION

摘要

PURPOSE: To improve the elongation-flanging properties of a steel sheet by forming a specified treated layer and a rust preventing oil layer on the surface of a high tensile strength cold rolled steel sheet with a specified compsn. and structure having high corrosion resistance and high workability. ;CONSTITUTION: On the surface of a steel sheet having a compsn. contg., by weight, 0.03 to 0.15% C, ≤0.05% Si, 0.50 to 1.20% Mn, 0.005 to 0.045% Nb, 0.005 to 0.100% Al and ≤0.010% S, and the balance Fe with inevitable impurities and having a structure in which the area ratio of a uniform and fine recrystallized ferrite structure having ≤20μm average grain size is regulated to ≥95%, an electrolytic chromated or coating chromated layer with 40 to 200mg/m² coating weight expressed in terms of metallic Cr and ≤5mg/m² alkali elutable Cr content is formed. Then, on its upper layer, a rust preventing oil layer with 0.1 to 5.0g/m² coating weight contg. inorganic lubricating grains and/or organic lubricating grains by 0.05 to 30% and 0.05 to 20% respectively and by 0.05 to 40% in total is furthermore formed. In this way, the steel sheet having excellent characteristics can be produced at a low cost.;COPYRIGHT: (C)1994,JPO&Japio