| 简介 |
An ultra-high strength essentially boron-free steel having a tensile strength of at least about 900 MPa (130 Ksi), a toughness as measured by Charpy V-notch impact test at -40.degree.C (-40 .degree.F) of at least about 120 joules (90ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives : carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling (10) passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling (10) passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching (12 ) said plate to a suitable Quench Stop Temperature (16); and stopping said quenching and allowing said plate to air cool (18) to ambient temperature. |
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