| 摘要 |
PROBLEM TO BE SOLVED: To provide a chromium-free organic-coated steel sheet which has excellent black point rust resistance in a hot and humid environment, and further has excellent electric conductivity required for performances such as weldability and groundability. SOLUTION: In the organic-coated steel sheet, in which film defects and the generation of corrosion caused thereby are effectively suppressed by using a cold rolled steel sheet whose surface roughness after skinpass rolling is controlled to a specified range as a steel sheet shock in a specified film constitution, the surface of a cold rolled steel sheet subjected to skinpass rolling is provided with a zinc based or aluminum based plating film, and an organic resin film which does not contain hexavalanet chromium is formed on the surface of the plating film in a coating weight of 0.5 to 5.0 g/m<2> , the count number of crests having a wavelength of 100 to 150μm in the roughness of the surface of the cold rolled steel sheet RPVC transferred by a rolling roll for skinpass rolling is <=200 peak/inch, and also, the average surface roughness Ra thereof is <=1.5μm.
|
