| 摘要 |
An ultra-high strength, weldable, low alloy 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 micro-laminate microstructure comprising austenite film layers and fine-grained martensite/lower bainite laths, is prepared by heating a steel slab. The 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. The slab is then reduced to form a plate in one or more passes in a temperature range in which austenite recrystallizes. The plate is then finish rolled 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 Quench Stop Temperature (QST). The quenching is stopped and for a period of time, either by holding the plate substantially isothermally at the QST or slow-cooling the plate before air cooling, or simply air cooling the plate to ambient temperature.
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