Posco Co., Ltd

Posco

Tae-Kyo Han

Jin-Keun Oh

Jong-Sang Kim

Kyoo-Young Lee

Jae-Hoon Lee

Sang-Deok Kang

Yong-Jin Kim

Sung-Kyu Kim

Young-Roc Im

Un-Hae Lee

Jong-Chan Park

Tae-Oh Lee

Jong-Kweon Kim

Sang-Hwan Lee

Il-Hyun Kim

Provided is a steel sheet which can be used for automobile parts and the like, and relates to a steel sheet having a superior balance of strength and ductility and strength and hole expansion ratio and superior bending formability, and a method for manufacturing same.

High strength steel sheet having superior workability and method for manufacturing same

Provided is a high-strength steel sheet including: 0.12% to less than 0.17% of carbon (C), 0.3% to 0.8% of silicon (Si), 2.5% to 3.0% of manganese (Mn), 0.4% to 1.1% of chromium (Cr), 0.01% to 0.3% of aluminum (Al), 0.01% to 0.03% of niobium (Nb), 0.01% to 0.03% of titanium (Ti), 0.001% to 0.003% of boron (B), 0.04% or less of phosphorus (P), 0.01% or less of sulfur(S): 0.01% or less of nitrogen (N), and a balance of iron (Fe) and inevitable impurities. The contents of C, Si, and Al satisfy: [C]+([Si]+[Al])/5≤0.35 wt %. A microstructure includes more than 1% to 4% or less of retained austenite, more than 10% to 20% or less of fresh martensite, 5% or less (excluding 0%) of ferrite, more than 50% to 70% or less of tempered martensite, and a balance of bainite.

High-strength steel sheet and manufacturing method thereof

A high-strength austenite-based high-manganese steel material and a manufacturing method for the same, the steel material comprising: manganese (Mn): 20 to 23 wt %, carbon (C): 0.3 to 0.5 wt %, silicon (Si): 0.05 to 0.50 wt %, phosphorus (P): 0.03 wt % or less, sulfur (S): 0.005 wt % or less, aluminum (Al): 0.050 wt % or less, chromium (Cr): 2.5 wt % or less, boron (B): 0.0005 to 0.01 wt %, nitrogen (N): 0.03 wt % or less, and a balance of iron (Fe) and other inevitable impurities, wherein stacked defect energy (SFE) represented by the following relationship 1 is 3.05 mJ/mor more, and a microstructure comprises 95 area % or more (including 100 area %) of austenite, and comprises 6 area % or more of strain grain boundaries in an austenite recrystallized grain, is provided.SFE(mJ/m)=&#x2212;24.2+0.950*Mn+39.0*C&#x2212;2.53*Si&#x2212;5.50*Al&#x2212;0.765*Cr&#x2003;&#x2003;[Relationship 1]where Mn, C, Cr, Si, and Al denote weight percent of respective components.

High-strength austenite-based high-manganese steel material and manufacturing method for same

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Gwangyang-si, South Korea

Tae-Kyo Han