Hot rolled steel product and method for producing same
AssigneeInland Steel Company
InventorsWilliam E. Heitmann, Richard J. Sulewski
Life of this patent
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Abstract
A hot rolled, high strength, low alloy steel strip is prepared from a steel having a controlled composition employing small quantities of Cb and V, and the steel is renitrogenized. Deliberate Si addition is avoided. The carbon and manganese contents are controlled, and a sulfur controlling agent is employed. Hot rolling practice is controlled. The hot rolled steel strip has a microstructure consisting essentially of a ferrite matrix with scattered pearlite, a relatively fine ferrite grain size and excellent yield strength and ductility.
Claims13
A hot-rolled steel strip having a composition consisting essentially of, in wt.%:
- carbon--0.04-0.08
- manganese--1.1-1.6
- columbium--from about 0.03 to less than about 0.08
- vanadium--0.08-0.1
- nitrogen--0.013-0.020
- silicon--less than 0.05
- sulfur--less than 0.02
- phosphorus--less than 0.02
- aluminum--0.02-0.10
- iron--essentially the balance
- said steel strip having a microstructure consisting essentially of a ferrite matrix as a major portion and scattered pearlite as a minor portion;
- said composition including a sulfur controlling agent;
- said microstructure having a ferrite grain size at least as fine as ASTM 12;
- said steel strip having a yield strength of at least 80 ksi (545 MPa), and an elongation of at least 20% in 2 inches (5 cm).
A method for producing a hot rolled steel strip having a microstructure consisting essentially of a ferrite matrix as a major portion and scattered pearlite as a minor portion, a ferrite grain size at least as fine as ASTM 12, a yield strength of at least 80 ksi (550 MPa) and an elongation of at least 20% in 2 inches (5 cm), said method comprising the steps of:
- providing a steel slab having a composition consisting essentially of, in wt.%:
- carbon--0.04-0.08
- manganese--1.1-1.6
- columbium--from about 0.03 to less than about 0.08
- vanadium--0.08-0.1
- nitrogen--0.013-0.020
- silicon--less than 0.05
- sulfur--less than 0.02
- phosphorus--less than 0.02
- aluminum--0.02-0.10
- iron--essentially the balance
- said composition including a sulfur controlling agent;
- heating said slab to a mean slab temperature in the range of about 1204.degree. to 1316.degree. C. (2200.degree. to 2400.degree. F.);
- hot rolling said slab to produce an intermediate strip having a thickness substantially less than said slab but substantially greater than the desired final thickness of said strip, said intermediate strip having a strip temperature, at the end of said hot rolling step, greater than about 1049.degree. C. (1920.degree. F.);
- cropping the ends from said intermediate strip;
- subjecting said intermediate strip to finish hot rolling to reduce said strip to said desired final thickness;
- said intermediate strip having a strip temperature no less than about 982.degree. C. (1800.degree. F.) at the beginning of said finish hot rolling, and said strip having a strip temperature no less than about 899.degree. C. (1650.degree. F.) at the end of the finish hot rolling;
- cooling said strip after said finish hot rolling to a strip temperature below about 621.degree. C. (1150.degree. F.);
- and collecting said strip at a strip temperature below about 621.degree. C. (1150.degree. F.).
Dependencies are inferred from the claim text.