| 摘要 |
PROBLEM TO BE SOLVED: To produce a low carbon cold rolled steel sheet excellent in stretch rigidity which is the rigidity of press parts such as an automobile outer board panel having a relatively slowly curved face and having an extremely large area against the sheet thickness in the case external force is acted on press parts made from the same. SOLUTION: As to this low carbon cold rolled steel sheet excellent in formability and stretch rigidity, in a cold rolled steel sheet containing, by mass, >0.01 to 0.05% C and having a sheet thickness of 0.5 to 0.8 mm and yield stress of 120 to 250 N/mm2, after prestrain of 2% by relative strain is applied, and heat treatment is performed at 150 to 170 deg.C for 5 to 20 min, the ratio between the inclination X of the stress-strain curve at a strain amount of 0.06% and the Young's modulus Y in the case a tensile test is again performed, i.e., A(=X/Y) satisfies A>0.8, and the increased amount of the yield stress after the heat treatment is >=40 N/mm2.
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