Formable high strength low alloy steel

Claim 1

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 2

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 3

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength to a value in the vicinity of its original value.

Claim 4

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength to a value in the vicinity of its original value.

Claim 5

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 6

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 7

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength and tensile strength to values greater than their original values.

Claim 8

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength and tensile strength to values greater than their original values.

Claim 9

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a temperature above 1350° F. for a time sufficient to dissolve a substantial proportion of said constituents without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the ultimate strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and aging said deformed steel by the equivalent of heating said deformed steel to a temperature of 400° F. for at least 5 minutes to increase the yield strength and tensile strength to values greater than their original values.

Claim 10

The method of producing a high strength low alloy steel having improved formability comprising the steps of: heating a high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a temperature above 1350° F. for a time sufficient to dissolve a substantial proportion of said constituents without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the ultimate strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and aging said deformed steel by the equivalent of heating said deformed steel to a temperature of 400° F. for at least 5 minutes to increase the yield strength and tensile strength to values greater than their original values.

Claim 11

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a thickness of less than 0.075 inch, heating said cold rolled steel to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 12

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a thickness of less than 0.075 inch, heating said cold rolled steel to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 13

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to a thickness of less than 0.075 inch, heating said cold rolled steel to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperatures to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 14

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to a thickness of less than 0.075 inch, heating said cold rolled steel to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperatures to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 15

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a thickness of less than 0.075 inch, heating said cold rolled steel to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase to the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength and tensile strength to values greater than their original values.

Claim 16

The method of producing a high strength low alloy steel having improved formability comprising the steps of: cold rolling a hot rolled high strength low alloy steel having alloy constituents taken from the group consisting of the carbide, nitride and carbonitride of vanadium to a thickness of less than 0.075 inch, heating said cold rolled steel to the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then air cooling said steel to substantially room temperature so as to reduce the yield strength to about 55 ksi or less and improve formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% on the tensile stress-strain diagram to effect a substantial increase to the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength and tensile strength to values greater than their original values.

Claim 17

The method of producing an SAE 980X high strength low alloy steel having improved formability comprising the steps of: heating an SAE 980X high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 18

The method of producing an SAE 980X high strength low alloy steel having improved formability comprising the steps of: heating an SAE 980X high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof and plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation.

Claim 19

The method of producing an SAE 980X high strength low alloy steel having improved formability comprising the steps of: heating an SAE 980X high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength to a value in the vicinity of its original value.

Claim 20

The method of producing an SAE 980X high strength low alloy steel having improved formability comprising the steps of: heating an SAE 980X high strength low alloy steel having alloy constituents taken from the group consisting of the carbides, nitrides and carbonitrides of the metals taken from the group consisting of V, Ti, and Nb to at least the lowermost eutectoid temperature of said steel for a time sufficient to at least partially transform the microstructure of said steel from ferrite to austenite and to dissolve a substantial proportion of said constituents into the austenite without appreciable ferrite grain growth and then cooling said steel to substantially room temperatures so as to substantially lower the yield strength and improve the formability of said steel while maintaining the tensile strength thereof; plastically deforming said steel an amount equivalent to at least 2% strain on the tensile stress-strain diagram to effect a substantial increase in the yield strength after said deformation, and heating said deformed steel to a temperature and for a time sufficient to increase the yield strength to a value in the vicinity of its original value.