Patent ID: 6187117
Filing Date: 2001-02-13
Classification: C21D,C22C

Abstract:
A method of making an as-rolled and cooled weathering grade steel plate comprising:a) selecting a minimum yield strength:plate thickness target from one of 50 KSI:up to 4 inches, 65 KSI:up to 1.5 inches, and 70 KSI:up to 1.25 inches;b) providing a heated shape consisting essentially of, in weight percent:from about 0.05% to about 0.12% carbon;from about 0.50% to about 1.35% manganese;up to about 0.04% phosphorous;up to about 0.05% sulfur;from about 0.15% to about 0.65% silicon;from about 0.20% to about 0.40% copper;from greater than zero to up to about 0.50% nickel;from about 0.40% to about 0.70% chromium;from about 0.01% to about 0. 10% vanadium;from about 0.01% to about 0.05% niobium;from about 0.005% to about 0.02% titanium;an amount of aluminum up to about 0.1%;from about 0.001% to about 0.015% nitrogen;with the balance iron and incidental impurities;c) rough rolling the heated shape above the recrystallization stop temperature to an intermediate gauge plate;d) finish rolling the intermediate gauge plate from an intermediate temperature below the recrystallization stop temperature to a finish rolling temperature above the Ar.sub.3 temperature to produce a final gauge plate;e) subjecting the final gauge plate to one of air or accelerated cooling when the minimum yield strength plate thickness target is 50 KSI:up to 4 inches, and liquid media accelerated cooling when the yield strength:plate thickness target is one of 65 KSI:up to 1.5 inches and 70 KSI:up to 1.25 inches, the air cooling having a start cooling temperature above the Ar.sub.3 temperature, and the accelerated cooling having a start cooling temperature above the Ar.sub.3 temperature, and finishing cooling temperature below the Ar.sub.3 temperature.