Patent ID: 6238493
Filing Date: 2001-05-29
Classification: C21D,C22C

Abstract:
A method of making an as-rolled and cooled weathering grade steel plate comprising:providing a heated slab consisting essentially of, in weight percent,from about 0.05% to about 0.12% carbon;from about 1.00% to about 1.80% manganase;up to about 0.035% phosphorus;up to about 0.040% sulfur;from about 0.15% to about 0.65% silicon;from about 0.20% to about 0.40% copper;an amount of nickel up to about 0.50%;from about 0.40% to about 0.70% chromium;up to about 0.20% molybdenum;from about 0.055% to about 0.09% niobium;from about 0.005% to about 0.02% titanium;an amount of aluminum up to 0.10%;from about 0.001% to about 0.015% nitrogen;with the balance iron and incidental impurities;rough rolling the heated slab above the recrystallization stop temperature to an intermediate gauge plate;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 having a thickness up to about 4 inches; andsubjecting the final gauge plate to at least liquid media accelerated cooling having a start cooling temperature above the Ar.sub.3 temperature and a finishing cooling temperature below the Ar.sub.3 temperature to form a weathering grade plate having a minimum of 70 KSI yield strength, 90-110 KSI tensile strength and a Charpy V-notch toughness greater than 35 ft-lbs. at -10.degree. F.