Nucor Corporation

Other

James W Watson

Walter N Blejde

Harold Bradley Rees

Tao Wang

Eric Young

Paul Kelly

Chad Baudendistel

Christopher Ronald Killmore

Mike Schueren

David C Van Aken

Ronald K Kirby

This application discloses thin metal strips and methods of making thin metal strip. Particular embodiments of such methods include cooling the thin metal strip to a temperature equal to or less than a bainite or a martensite start transformation temperature Bor Mto thereby form bainite and/or martensite, respectively, within the thin metal strip, reheating the thin metal strip to a reheat temperature equal to or greater than transformation temperature Acand holding the thin metal strip at the reheat temperature for at least 2 seconds and thereby forming austenite within the thin metal strip with at least 75% of austenite grains having a grain size equal to or less than 15 &#x3bc;m, and rapidly recooling the thin metal strip to a temperature equal to or less than the martensite start transformation temperature Mand thereby providing finer martensite within the thin metal strip from a finer prior austenite.

Thermal cycling for austenite grain refinement

A hot rolled light-gauge martensitic steel sheet made by the steps comprising: (a) preparing a molten steel melt comprising: (i) by weight, between 0.20% and 0.35% carbon, less than 1.0% chromium, between 0.7% and 2.0% manganese, between 0.10% and 0.50% silicon, between 0.1% and 1.0% copper, less than 0.05% niobium, less than 0.5% molybdenum, and silicon killed containing less than 0.01% aluminum, and (ii) the remainder iron and impurities resulting from melting; (b) solidifying at a heat flux greater than 10.0 MW/mand cooling the molten melt into a steel sheet less than 2.0 mm in thickness in a non-oxidizing atmosphere to below 1080&#xb0; C. and above Artemperature at a cooling rate greater than 15&#xb0; C./s; and (c) hot rolling the steel sheet to between 15% and 50% reduction and rapidly cooling.

Hot rolled light-gauge martensitic steel sheet and method for making the same

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%.

A method of making printed circuit boards in a continuous process. The method uses copper base metal sputtered onto a substrate. This base metal is much thinner than the base metal normally used in printed circuit processes and ultimately allows a greater number of conductors per unit of length to be made on the boards.

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Brownsburg, IN, United States of America

James W Watson