| 摘要 |
An ultra-high strength, weldable, low alloy steel, containing less than 9 wt% nickel, with excellent cryogenic temperature toughness in the base plate and in the heat affected zone (HAZ) when welded, having a tensile strength greater than about 830 MPa (120 ksi) and a microstructure comprising predominantly tempered fine-grained lath martensite, tempered fine-grained lower bainite, tempered fine granular bainite (FGB), or mixtures thereof, 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; finish rolling the plate in one or more passes in a temperature range below the austenite recrystallization temperature and above the AR3 transformation temperature; quenching the finish rolled plate to a suitable Quench Stop Temperature; stopping the quenching; and tempering the plate at a suitable temperature for a period of time sufficient to cause precipitation of hardening particles.
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