摘要 |
<p>An ultra-high strength, weldable, low alloy, dual phase steel with excellent cryogenic temperature toughness in the base plate and in the heat affected zone (HAZ) when welded, having a tensile strength greater than 830 MPa (120 Ksi) and a microstructure comprising a ferrite phase (14) and a second phase of predominantly lath martensite and lower bainite (16), is prepared by heating a steel slab comprising iron and specified weight percentages of some or all of the additives, carbon, manganese, nickel, nitrogen, copper, chromium, molybdenum, silicon, niobium, vanadium, titanium, aluminum and boron; reducing the slab to form plate in one or more passes in a temperature range in which austenite recrystallizes; further reducing the plate in one or more passes in a temperature range below the austenite recrystallization temperature and above the Ar3 transformation temperature; finish rolling the plate between the Ar3 transformation temperature and the Arl transformation temperature; quenching the finish rolled plate to a suitable Quench Stop Temperature (QST); and stopping the quenching.</p> |