Low silicon high strength low alloy steel

Claim 1

A killed high strength low alloy steel product having been hot-rolled to a thickness, spray cooled, and collected immediately thereafter at temperature of from 950° to 1300° F.; having a composition consisting essentially of from 0.09% to 0.22% carbon, 1.65% maximum manganese, 0.05% maximum silicon, 0.25% maximum sulfur, from 0.015% to 0.031% nitrogen, from 0.10% to 0.14% vanadium, from 0.01% to 0.10% rare earth or rare earth mixture, 0.01% to 0.09% aluminum, balance iron; said steel composition, thickness and collection temperature also satisfying the following relationship; YS ≦98,430+182,310 (V)+80,662 (C) + 433,220 (N) -36.7 (CT)-26,184(T) -92,543 (Al), wherein, Ys = yield Strength and is 88,776 p.s.i.; V = % vanadium; C = % carbon; N = % nitrogen; Ct = collection Temperature, ° F; T = hot-Rolled Thickness, inches; and Al = % Aluminum; and said steel product having an ultimate tensile strength of 95,000 p.s.i. minimum, a yield strength of 80,000 p.s.i. minimum and ductility as measured by percent elongation (2 inches) 18% minimum; and being substantially free of macroscopic rare earth oxy-sulfide inclusions.

Claim 9

A method of producing a high strength low alloy steel product, comprising: a. hot rolling a killed steel having a composition consisting essentially of from 0.09% to 0.22% carbon, 1.65% maximum manganese, 0.05% maximum silicon, 0.025% maximum sulfur, from 0.015% to 0.31% nitrogen, from 0.10% to 0.14% vanadium, from 0.01% to 0.10% rare earth or rare earth mixture, 0.01% to 0.09% aluminum, balance iron to a thickness at a finishing temperature of above the Ar 3 temperature of the steel to about 1700° F., spray cooling said hot-rolled steel at a rate of from 20° F. to 135° F. per second, and collecting said hot-rolled steel at a temperature of from 950° F. to 1300° F. immediately upon termination of spray cooling so as to produce a hot-rolled product having an ultimate tensile strength of 95,000 p.s.i. minimum, a yield strength of 80,000 p.s.i. minimum, and ductility as measured by percent elongation (2 inches) of 18% minimum and substantially free of macroscopic rare earth oxy-sulfides inclusions, said steel composition, thickness and collection temperature also satisfying the following relationship: YS ≦98,430+182,310 (V)+80,662 (C)+433,220 (N)- 36.7(CT)-26,184(T) -92,543 (Al), wherein, Ys = yield Strength and is 88,776 p.s.i. V = % vanadium; C = % carbon; N = % nitrogen; Ct = collection Temperature, ° F; T = hot-Rolled Thickness, inches; and Al = % Aluminum.

Claim 10

A method of producing a high strength low alloy steel product, comprising: a. hot rolling a killed steel having a composition consisting essentially of from 0.09% to 0.22% carbon, 1.65% maximum manganese, 0.05% maximum silicon, 0.025% maximum sulfur, from 0.015% to 0.31% nitrogen, from 0.10% to 0.14% vanadium, from 0.01% to 0.10% rare earth or rare earth mixture, 0.01% to 0.09% aluminum, balance iron to a thickness at a finishing temperature of above the Ar 3 temperature of the steel to about 1700° F., spray cooling said hot-rolled steel at a rate of from 20° F. to 135° F. per second, and collecting said hot-rolled steel at a temperature of from 950° F. to 1300° F. immediately upon termination of spray cooling so as to produce a hot-rolled product having an ultimate tensile strength of 95,000 p.s.i. minimum, a yield strength of 80,000 p.s.i. minimum, and ductility as measured by percent elongation (2 inches) of 18% minimum and substantially free of macroscopic rare earth oxy-sulfides inclusions, said steel composition, thickness and collection temperature also satisfying the following relationship: YS ≦98,430+182,310 (V)+80,662 (C)+433,220 (N)- 36.7(CT)-26,184(T) -92,543 (Al), wherein, Ys = yield Strength and is 88,776 p.s.i. V = % vanadium; C = % carbon; N = % nitrogen; Ct = collection Temperature, ° F; T = hot-Rolled Thickness, inches; and Al = % Aluminum.