Patent ID: 7736447
Filing Date: 2010-06-15
Classification: C21D,C22C

Abstract:
1. Steel plate for ultra-high-strength linepipe having excellent low-temperature toughness consisting essentially of: and the remainder being iron and unavoidable impurities and having the value P defined below being between 2.5 and 4.0, and having a microstructure composed of degenerate upper bainite of more than 70%, in which; the ratio (Hv-avep)/(Hv-M) between the average Vickers hardness Hv-avep in the direction of thickness and the martensitic hardness Hv-M determined by carbon content is between 0.8 and 0.9, and the transverse tensile strength TS-Tp is between 880 MPa and 1080 MPa, wherein the symbols of elements designate the mass % of the individual elements.