| 摘要 |
PURPOSE:To prevent generation of surface roughening by adequately controlling the pattern of the surface roughness of a steel sheet which is specified in an average crystal grain size, thereby improving press formability and relieving a local stress concentration. CONSTITUTION:The surface roughness of the thin steel sheet for press forming having <=20mum average crystal grain size is adjusted to the geometric surface structure satisfying the relation in which the surface roughness of the steel sheet is <=0.25S regularity parameter expressed by the equations I, II in at least one direction and >=1.2mum Ra average surface roughness. In the equations, Xi is the inter-peak distance in the projecting parts of the steel sheet surface. The regular local strains are thereby incorporated into the steel sheet surface and the generation of the surface roughening is effectively prevented even with the steel sheet having coarse grain sizes.
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