| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high strength cold rolled sheet steel having high strength and good processability and excellent in chemical conversion properties and corrosion resistance after electrodeposition coating, and to provide a method for producing the same. <P>SOLUTION: The method for producing the cold rolled sheet steel includes hot-rolling, cold-rolling, and continuously annealing a slab having a component composition comprising 0.05-0.30 mass% C, 0.8-3.0 mass% Si, 1.5-3.0 mass% Mn, 0.10 mass% or less P, 0.01 mass% or less S, 0.01-0.1 mass% Al, 0.005 mass% or less N, and the balance consisting of Fe and inevitable impurities. After the above continuous annealing, the sheet steel is washed with an acid to remove 1μm or more per one side of steel sheet surfaces. The maximum value P<SB>2</SB>of the Si concentration on the steel sheet surface and the portion inside the steel sheet in 1μm deep from the surfaces is 1.3 or less times the Si concentration P<SB>1</SB>at the position of 1/4 of the sheet thickness. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
