Patent ID: 8840834
Filing Date: 2014-09-23
Classification: C21D,C22C,C23C

Abstract:
1. A high strength steel sheet comprising a composition including, on a mass basis: C: 0.12% or more and 0.50% or less; Si: 2.0% or less; Mn: 1.0% or more and 5.0% or less; P: 0.1% or less; S: 0.07% or less; Al: 1.0% or less; and N: 0.008% or less, with the balance Fe and incidental impurities, with a steel microstructure including on an area ratio basis, 80% or more of autotempered martensite, less than 5% of ferrite, 10% or less of bainite, and 5% or less of retained austenite; and the mean number of precipitated iron-based carbide grains each having a size of 5 nm or more and 0.5 μm or less and included in the autotempered martensite is 7 ×10