Nucor Corporation

Chad Baudendistel

Tao Wang

James W Watson

Eric Young

A weathering steel made by preparing a molten melt producing an as-cast carbon alloy steel strip with a corrosion index of at least 6.0 comprising, by weight, 0.02%-0.08% carbon, &#x3c;0.6% silicon, 0.2%-2.0% manganese, &#x3c;0.03% phosphorus, &#x3c;0.01% sulfur, &#x3c;0.01% nitrogen, 0.2%-0.5% copper, 0.01%-0.2% niobium, 0.01%-0.2% vanadium, 0.1%-0.4% chromium, 0.08%-0.25% nickel, &#x3c;0.01% aluminum, and the remainder iron and impurities. The molten melt is solidified and cooled into a cast strip 4 mm in thickness in a non-oxidizing atmosphere. The strip is hot rolled in an austenitic temperature range above Arto between 10% and 50% reduction, cooled at above 20&#xb0; C./s and coiled below 700&#xb0; C. to form a steel strip with a microstructure comprising bainite and acicular ferrite with more than 70% niobium in solid solution. Then, age hardening the strip resulting in a yield strength of at least 550 MPa and a total elongation of at least 8%.

Weathering steel

A method of making weathering steel by preparing a molten melt producing an as-cast carbon alloy steel strip with a corrosion index of at least 6.0 comprising, by weight, 0.02%-0.08% carbon, &#x3c;0.6% silicon, 0.2%-2.0% manganese, &#x3c;0.03% phosphorus, &#x3c;0.01% sulfur, &#x3c;0.01% nitrogen, 0.2%-0.5% copper, 0.01%-0.2% niobium, 0.01%-0.2% vanadium, 0.1%-0.4% chromium, 0.08%-0.25% nickel, &#x3c;0.01% aluminum, and the remainder iron and impurities. The molten melt is solidified and cooled into a cast strip &#x2264;4 mm in thickness in a non-oxidizing atmosphere. The strip is hot rolled in an austenitic temperature range above Arto between 10% and 50% reduction, cooled at above 20&#xb0; C./s and coiled below 700&#xb0; C. to form a steel strip with a microstructure comprising bainite and acicular ferrite with more than 70% niobium in solid solution. Then, age hardening the strip resulting in a yield strength of at least 550 MPa and a total elongation of at least 8%.

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Charlotte, NC, United States of America

Chad Baudendistel