Patent ID: 8911567
Filing Date: 2014-12-16
Classification: B32B,C21D,C22C,C23C,Y10T

Abstract:
1. A high-strength steel sheet comprising, by mass %: C: 0.01% to 0.10%; Si: 0.15% or less; Mn: 0.80% to 1.50%; P: 0.10% or less; S: 0.015% or less; Al: more than 0.20% to 0.80%; Cr: 0.01% to 0.40%; N: 0.0100% or less; and a balance consisting of iron and unavoidable impurities, wherein: a metallic structure is composed of ferrite and a hard second phase; an area fraction of the ferrite is 80% or more; an area fraction of the hard second phase is 1% to 20%; a fraction of unrecrystallized ferrite in the ferrite is less than 10%; ferrite grain sizes are 5 μm to 20 μm; and a fraction of ferrite crystal grains having an aspect ratio of 1.2 or less in entire ferrite crystal grains is 60% or more.