HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT LOCAL DEFORMABILITY AND MANUFACTURING METHOD THEREOF

摘要

This high-strength cold-rolled steel sheet contains, in mass %, C: 0.02% to 0.20%; Si: 0.001% to 2.5%; Mn: 0.01% to 4.0%; P: 0.001% to 0.15%; S: 0.0005% to 0.03%; Al: 0.001% to 2.0%; N: 0.0005% to 0.01%; and O: 0.0005% to 0.01%; in which Si+Al is limited to less than 1.0%, and a balance being composed of iron and inevitable impurities, in which an area ratio of bainite in a metal structure is 95% or more, at a sheet thickness center portion being a range of ⅝ to ⅜ in sheet thickness from the surface of the steel sheet, an average value of pole densities of the {100}<011> to {223}<110> orientation group is 4.0 or less, and a pole density of the {332}<113> crystal orientation is 5.0 or less, and a mean volume diameter of crystal grains in the metal structure is 7 μm or less.

主权项

1. A high-strength cold-rolled steel sheet having excellent local deformability comprising:
in mass %,
C: not less than 0.02% nor more than 0.20%;Si: not less than 0.001% nor more than 2.5%;Mn: not less than 0.01% nor more than 4.0%;P: not less than 0.001% nor more than 0.15%;S: not less than 0.0005% nor more than 0.03%;Al: not less than 0.001% nor more than 2.0%;N: not less than 0.0005% nor more than 0.01%; andO: not less than 0.0005% nor more than 0.01%; in which Si+Al is limited to less than 1.0%, anda balance being composed of iron and inevitable impurities, whereinan area ratio of bainite in a metal structure is 95% or more,at a sheet thickness center portion being a range of ⅝ to ⅜ in sheet thickness from the surface of the steel sheet, an average value of pole densities of the {100}<011> to {223}<110> orientation group represented by respective crystal orientations of {100}<011>, {116}<110>, {114}<110>, {113}<110>, {112}<110>, {335}<110>, and {223}<110> is 4.0 or less, and a pole density of the {332}<113> crystal orientation is 5.0 or less, anda mean volume diameter of crystal grains in the metal structure is 7 μm or less.