US 12,325,902 B2
Ultra-high strength weathering steel and high friction rolling of the same
Tao Wang, Germantown, TN (US); and Kishlay Mishra, Memphis, TN (US)
Assigned to Nucor Corporation, Charlotte, NC (US)
Filed by NUCOR CORPORATION, Charlotte, NC (US)
Filed on Sep. 20, 2019, as Appl. No. 16/576,924.
Claims priority of provisional application 62/902,825, filed on Sep. 19, 2019.
Claims priority of provisional application 62/830,000, filed on Apr. 5, 2019.
Claims priority of provisional application 62/830,021, filed on Apr. 5, 2019.
Claims priority of provisional application 62/811,153, filed on Feb. 27, 2019.
Claims priority of provisional application 62/802,900, filed on Feb. 8, 2019.
Prior Publication US 2020/0255927 A1, Aug. 13, 2020
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/42 (2006.01); C21D 8/02 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/44 (2006.01); C22C 38/48 (2006.01); C22C 38/58 (2006.01); E02D 5/28 (2006.01)
CPC C22C 38/42 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0278 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/44 (2013.01); C22C 38/48 (2013.01); C22C 38/58 (2013.01); E02D 5/28 (2013.01); C21D 2211/002 (2013.01); C21D 2211/008 (2013.01)] 15 Claims
 
1. A continuously cast hot rolled ultra-high strength weathering thin cast steel strip comprising:
an as cast thickness cast at less than or equal to 2.5 mm;
a composition comprising: by weight, between 0.20% and 0.40% 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 or equal to 0.12% niobium, less than 0.5% molybdenum, between 0.5% and 1.5% nickel, and silicon killed containing less than 0.01% aluminum, and the remainder iron and impurities resulting from melting;
a corrosion index of 6.0 or greater;
a microstructure having, by volume, at least 75% martensite formed from prior austenite grain sizes of at least 100 μm, a yield strength of between 700 and 1600 MPa, a tensile strength of between 1000 and 2100 MPa, and an elongation of between 1% and 10%; and
a pair of hot rolled opposing surfaces wherein less than 50% of the pair of opposing surfaces contain prior austenite grain boundaries.