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|1. (WO2018025674) HIGH-STRENGTH STEEL PLATE AND MANUFACTURING METHOD THEREOF|
|Applicants:||KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)
|Title:||HIGH-STRENGTH STEEL PLATE AND MANUFACTURING METHOD THEREOF|
This high-strength steel plate contains C: 0.15-0.35 mass%, total of Si and Al: 0.5-3.0 mass%, Mn: 1.0-4.0 mass%, P: 0.05 mass% or less and S: 0.01 mass% or less, the remainder being Fe and unavoidable impurities. In the steel composition, the ferrite fraction is 5% or less, the total fraction of tempered martensite and tempered bainite is 60% or higher, the amount of retained austenite is 10% or greater, the average size of MA is 1.0 μm or less, the average size of the retained austenite is 1.0 μm or less, the retained austenite with a size of greater than or equal to 1.5 μm is at least 2% of the total amount of retained austenite, and the scattering intensity in small-angle X-ray scattering with a q-value of 1 nm-1 is less than or equal to 1.0 cm-1.