| 摘要 |
PURPOSE:To improve press formability and chemical conversion treatability even with the steel sheet consisting of the same material by providing a regular roughness pattern to the surface of the steel sheet and further controlling the average surface roughness and average valley spacing thereof. CONSTITUTION:The regularity parameter S indicating the regularity of the surface roughness of the steel sheet expressed by the equation is specified to S<=0.25 in at least one direction. The average surface roughness Ra(mum) and the average valley spacing Lmv(mum) satisfy the relation RaXLmv>=50. In the equation, Xi denotes the distance between the peaks of the projections on the steel sheet surface. The cold rolled steel sheet having the excellent press formability and chemical conversion treatability is thus obtd.
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