| 摘要 |
PURPOSE:To improve mold galling resistance and to improve the sharpness in coating after molding by adjusting the wavelength component strength and crystal grain size number of the steel sheet with roughened surface within a specific range. CONSTITUTION:The steel sheet is temper-rolled by dull finishing rolls by a high-density energy beam and is thereby formed to <=85% area ratio of flat parts 3a occupying in the total area of the plan view of the steel sheet and >=4mum depth from the flat parts 3a to annular valley parts. The wavelength component strength Pmum<2> of the wavelength lambda included in 585mum<=lambda<2,730mum when the surface shapes of the steel sheet are subjected to a frequency analysis and the crystal grain size number N of the steel sheet are so determined as to satisfy equation. As result, the surface-roughened steel sheet having the good mold galling resistance and the excellent sharpness in coating after molding is obtd. |
