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|1. (WO2017065371) HIGH STRENGTH STEEL SHEET AND MANUFACTURING METHOD THEREFOR|
|Applicants:||SAMHWA STEEL CO., LTD.
|Inventors:||AHN, Soon Tae
|Title:||HIGH STRENGTH STEEL SHEET AND MANUFACTURING METHOD THEREFOR|
The present invention relates to a high strength steel sheet having a tensile strength of 700 to 1,300 Mpa and an elongation of 12% or more, and having a tempered martensite single phase structure. The steel sheet of the present invention is manufactured through the steps of: rapidly heating a material steel sheet for 3 to 60 seconds to an Ac3 transformation point or higher and maintaining the material steel sheet, the material steel sheet containing 0.08 to 0.30 wt% of C, 0.01 to 2.0 wt% of Si, 0.30 to 3.0 wt% of Mn, 0.05 wt% or less of P and 0.05 wt% or less of S and the remainder being Fe and other unavoidable impurities; rapidly cooling the heated steel sheet to 100°C/s or higher with water or oil; and rapidly tempering to 500°C to A1 transformation point for 3 to 60 seconds including heating and maintaining time.