HOT-ROLLED STEEL SHEET AND PRODUCTION METHOD THEREFOR, COLD-ROLLED STEEL SHEET AND PRODUCTION METHOD THEREFOR, PRODUCTION METHOD FOR COLD-ROLLED ANNEALED STEEL SHEET, AND PRODUCTION METHOD FOR HOT-DIP GALVANIZED STEEL SHEET

摘要

The present invention provides a cold-rolled steel sheet that exhibits excellent surface properties after press work while having high contents of Mn and P. The cold-rolled steel sheet according to the present invention has a prescribed component makeup comprising 0.2-2.0% of Mn and 0.005-0.060% of P. When ΔSm and ΔWm are calculated for each local maximum value in a width-direction profile of a Mn segregation degree Sm in the center part of sheet thickness, the average value and the standard deviation 2σm of ΔSm where ΔWm becomes at least 200 μm are at most 0.10 and at most 0.05, respectively. Here, Sm equals Mn concentration (%) at an arbitrarily defined point / average Mn concentration (%) in the steel sheet; ΔSm is the difference between a local maximum value of Sm and an average value of two local minimum values adjacent to said local maximum value; and ΔWm represents the width-direction distance between two local minimum values adjacent to each local maximum value. Likewise, in a width-direction profile of a P segregation degree Sp in the center part of sheet thickness, the average value is at most 0.20 and the standard deviation 2σp is at most 0.10.