High-strength steel sheet with excellent delayed fracture resistance and low-temperature toughness, and high-strength members manufactured using it

摘要

In mass%, C: 0.20 to 0.42%, Si: 0.06 to 0.5%, Mn: 0.2 to 2.2%, Cr: 0.1 to 2.5%, B: 0.0005-0.01%, O: 0.0020-0.020%, Al: 0.001-0.03%, Ti: 0.001-0.05%, N: 0.1% or less, P: 0.03% or less, S: 0.02% or less, the balance is composed of chemical components of Fe and inevitable impurities, and Mx oxide having a maximum length of 1 μm or more and 5 μm or less is 5 × 10 3 in steel. There are 1.7 × 10 2 / mm 2 or more of a composite oxide of Mn and Si having a length of 1 μm or more and a length of 10 μm or less in the minor axis direction. A high-strength steel sheet with a size of 103 / mm2 or less.