| 摘要 |
PURPOSE: An ultra-high strength steel sheet having superior hydrogen delayed fracture resistance and a manufacturing method thereof are provided to secure high tensile strength and elongation by minimizing the content of S in the steel sheet. CONSTITUTION: An ultra-high strength steel sheet having superior hydrogen delayed fracture resistance comprises C 012~025 weight%, Si 010~065 weight%, Mn 08~30 weight%, Al 001~100 weight%, P 0~002 weight%, S 0~0001 weight% or less, Cu 02~06 weight%, and Fe and inevitable impurities of the rest amount. A manufacturing method of the ultra-high strength steel sheet is as follows. A steel slab is re-heated and hot-rolled to obtain a hot-rolled steel sheet. The hot-rolled steel sheet is cooled to a set winding temperature at a set cooling speed. The cooled steel sheet is wound at the set winding temperature to obtain a hot-rolled coil.
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