Patent ID: 9005375
Filing Date: 2015-04-14
Classification: C21D,C22C

Abstract:
1. A cold-rolled steel sheet for cans having excellent surface roughening resistance, the steel sheet having a composition which contains by mass % 0.0060 to 0.01% C, 0.05% or less Si, more than 0.3 to 0.6% Mn, 0.02% or less P, 0.02% or less S, 0.01 to 0.10% Al, 0.0015 to 0.0050% N, 0.02 to 0.12% Nb and a balance of Fe and unavoidable impurities, wherein an average ferrite grain size in a cross section in the rolling direction in a region ranging from a surface layer of the steel sheet to a position ¼ of a sheet thickness away from the surface layer of the steel sheet is set to 7 μm or more and 10 μm or less, the average ferrite grain size in a cross section in the rolling direction in a region ranging from the position ¼ of a sheet thickness away from the surface layer of the steel sheet to a sheet thickness center portion of the steel sheet is set to 15 μm or less, and the average ferrite grain size in the cross section in the rolling direction in the region ranging from the surface layer of the steel sheet to the position ¼ of a sheet thickness away from the surface layer of the steel sheet is set smaller than the average ferrite grain size in the cross section in the rolling direction in a region ranging from the position ¼ of a sheet thickness away from the surface layer of the steel sheet to the sheet thickness center portion of the steel sheet.