Classes of steels for tubular products
View Patent ↗The present disclosure is directed and formulations and methods to provide alloys having relative high strength and ductility. The alloys may be provided in seamless tubular form and characterized by their particular alloy chemistries and identifiable crystalline grain size morphology. The alloys are such that they include boride pinning phases. In what is termed a Class 1 Steel the alloys indicate tensile strengths of 700 MPa to 1400 MPa and elongations of 10-70%. Class 2 Steel indicates tensile strengths of 800 MPa to 1800 MPa and elongations of 5-65%. Class 3 Steel indicates tensile strengths of 1000 MPa to 2000 MPa and elongations of 0.5-15%.
1. A method for forming a seamless tubular component comprising:
supplying a metal alloy comprising Fe at a level of 48.00 to 88.00 atomic percent, Ni at 0 to 16.00 atomic percent, Cr at 0 to 32.00 atomic percent, Mn at 0 to 21.00 atomic percent, B at 1.0 to 8.00 atomic percent, Si at 1.00 to 14.00 atomic percent;
melting said alloy and solidifying by 1) centrifugal casting or 2) atomization and billet formation to provide an alloy including a matrix grain size of 500 nm to 20,000 nm and a boride grain size of 25 nm to 500 nm;
mechanical stressing said alloy and heating said alloy and forming a seamless tubular component by 1) one or more of the following methods if solidified by centrifugal casting: hot extrusion and hot pilgering, or 2) one or more of the following methods if solidified by atomization and billet formation: piercing, pierce and roll, hot extrusion, cold extrusion, hot pilgering and cold pilgering, said seamless tubular component having at least one of the following grain size distributions and mechanical property profiles, wherein said boride grains provide pinning phases that resist coarsening of said matrix grains:
(a) matrix grain size of 500 nm to 20,000 nm, boride grain size of 25 nm to 500 nm, precipitation grain size of 1 nm to 200 nm wherein said alloy indicates a yield strength of 400 MPa to 1300 MPa, tensile strength of 700 MPa to 1400 MPa and tensile elongation of 10 to 70%; or
(b) refined matrix grain size of 100 nm to 2000 nm, precipitation grain size of 1 nm to 200 nm, boride grain size of 200 nm to 2,500 nm where the alloy has a yield strength of 300 MPa to 800 MPa.
2. The method of claim 1 wherein said melting is achieved at temperatures in the range of 1100° C. to 2000° C. and solidification is achieved by cooling in the range of 11×10 3 to 4×10 −2 K/s.
3. The method of claim 1 wherein said seamless tubular component is positioned in a vehicle.
4. The method of claim 1 wherein said alloy having said grain size distribution (b) is exposed to a stress that exceeds said yield strength of 300 MPa to 800 MPa wherein said refined grain size remains at 100 nm to 2000 nm, said boride grain size remains at 200 nm to 2500 nm, said precipitation grains remain at 1 nm to 200 nm, wherein said alloy indicates a yield strength of 400 MPa to 1700 MPa, tensile strength of 800 MPa to 1800 MPa and an elongation of 5% to 65%.
5. The method of claim 4 wherein said alloy indicates a strain hardening coefficient of 0.2 to 1.0.
6. The method of claim 4 wherein said seamless tubular component is positioned in a vehicle.
7. The method of claim 1 , wherein said Mn is present in the range of 5.25 to 21.0 atomic percent.
8. The method of claim 1 , wherein said hot extrusion after either 1) centrifugal casting or 2) atomization and billet formation is performed at a temperature in the range of 0.7 Tm to 0.9 Tm, where Tm is the melt temperature of said alloy.
9. A method for forming a seamless tubular component comprising:
(a) supplying a metal alloy comprising Fe at a level of 48.0 to 88.0 atomic percent, Ni at 0.0 to 16.0 atomic percent, Cr at 0.0 to 32.0 atomic percent, Mn at 5.25 to 21.0 atomic percent, B at 1.0 to 8.0 atomic percent, Si at 1.0 to 14.0 atomic percent;
(b) melting said alloy and solidifying to provide an alloy including a matrix grain size of 500 nm to 20,000 nm and a boride grain size of 25 nm to 500 nm; and
(c) mechanical stressing said alloy and heating said alloy, forming a seamless tubular component by 1) one or more of the following methods if solidified by centrifugal casting: hot extrusion and hot pilgering, or 2) one or more of the following methods if solidified by atomization and billet formation: hot extrusion and hot pilgering,
wherein in heating said alloy, said alloy is heated a temperature in the range of 700° C. to 1200° C. and pressure is applied to said alloy and forming lath structure including grains of 100 nm to 10,000 nm and boride grain size of 100 nm to 2500 nm and said alloy has a yield strength of 300 MPa to 1400 MPa, tensile strength of 350 MPa to 1600 MPa and elongation of 0 to 12%.
10. The method of claim 9 wherein said melting is achieved at temperatures in the range of 1100° C. to 2000° C. and solidification is achieved by cooling in the range of 11×10 3 to 4×10 −2 K/s.
11. The method of claim 9 including heating the alloy after step (c) and forming lamellae grains 100 nm to 10,000 nm thick, 0.1-5.0 microns in length and 100 nm to 1000 nm in width along with boride grains of 100 nm to 2500 nm and precipitation grains of 1 nm to 100 nm, wherein said alloy indicates a yield strength of 300 MPa to 1400 MPa.
12. The method of claim 11 wherein said seamless tubular component is positioned in a vehicle.
13. The method of claim 11 wherein the alloy is stressed and forms an alloy having grains of 100 nm to 5000 nm, boride grains of 100 nm to 2500 nm, precipitation grains of 1 nm to 100 nm and said alloy has a yield strength of 500 MPa to 1800 MPa, a tensile strength of 1000 MPa to 2000 MPa and elongation of 0.5% to 15.0%.
14. The method of claim 13 wherein said alloy is positioned in a vehicle.
15. The method of claim 13 wherein said alloy indicates a strain hardening coefficient of 0.1 to 0.9.
16. The method of claim 9 wherein said seamless tubular component is positioned in a vehicle.