High friction rolling of thin metal strip
AssigneeNucor Corporation
InventorsTao Wang, Kishlay Mishra, Jeffery Edward Keffer
Life of this patent
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Abstract
Described herein are thin metal strips having hot rolled exterior side surfaces characterized as being primarily or substantially free of all prior austenite grain boundaries, or at least primarily or substantially free of all prior austenite grain boundaries, and including elongated surface structure. As a result, because the prior austenite grain boundaries are not primarily or substantially present, all such prior austenite grain boundaries are not susceptible to grain boundary etching due to acid etching or pickling. In particular examples, the thin metal strips undergo hot rolling performed with a coefficient of friction equal to or greater than 0.20 with or without use of lubrication.
Claims22
A hot rolled, thin cast steel strip comprising:
- opposing exterior side surfaces defining an as cast thickness of less than 5 mm between the opposing exterior side surfaces, the opposing exterior side surfaces being primarily free of all prior austenite grain boundaries and having a plurality of elongated surface structure formations formed by shear under a hot rolling coefficient of friction equal to or greater than 0.20 and elongated in a common direction, said common direction being a direction of hot rolling, to remove the prior austenite grain boundaries where the strip includes, by weight, 0.18% to 0.40% carbon, 0.7% to 1.2% manganese, 0.10% to 0.50% silicon, 0 to 0.1% vanadium, 0 to 0.1% niobium, 0 to 0.1% sulfur, 0 to 0.2% phosphorus, 0 to 0.5% chromium, 0.5 to 1.0% nickel, 0 to 0.5% copper, 0 to 0.15% molybdenum, 0 to 0.1% titanium, and 0 to 0.01% nitrogen, where the strip is a martensitic steel thin metal strip, and where the thin metal strip, after cooling, is characterized as having a tensile strength of 1100 to 2100 MPa, a yield strength of 900 to 1800 MPa, and an elongation to break of 3.5 to 8%.
A hot rolled, thin cast steel strip comprising:
- opposing exterior side surfaces defining an as cast thickness of less than 5 mm between the opposing exterior side surfaces, the opposing exterior side surfaces being primarily free of all prior austenite grain boundaries and having a plurality of elongated surface structure formations formed by shear under a hot rolling coefficient of friction equal to or greater than 0.20 and elongated in a common direction, said common direction being a direction of hot rolling, to remove the prior austenite grain boundaries where the strip includes, by weight, less than 0.25% carbon, 0.20 to 2.0% manganese, 0.05 to 0.50% silicon, less than or equal to 0.008% aluminum, and at least one element selected from the group consisting of titanium between 0.01 and 0.20%, niobium between 0.05 and 0.20%, and vanadium between about 0.01 and 0.20%.
A hot rolled, thin cast steel strip comprising:
- opposing exterior side surfaces defining an as cast thickness of less than 5 mm between the opposing exterior side surfaces, the opposing exterior side surfaces being primarily free of all prior austenite grain boundaries and having a plurality of elongated surface structure formations formed by shear under a hot rolling coefficient of friction equal to or greater than 0.20 and elongated in a common direction, said common direction being a direction of hot rolling, to remove the prior austenite grain boundaries where the strip includes, by weight, 0.18% to 0.40% carbon, 0.7% to 1.2% manganese, 0.10% to 0.50% silicon, 0 to 0.1% vanadium, 0 to 0.1% niobium, 0 to 0.1% sulfur, 0 to 0.2% phosphorus, 0 to 0.5% chromium, 0.5 to 1.0% nickel, 0 to 0.5% copper, 0 to 0.15% molybdenum, 0 to 0.1% titanium, and 0 to 0.01% nitrogen, and where the strip is a martensitic steel thin metal strip.
Dependencies are inferred from the claim text.