Claims
- 1. A high-strength, high-toughness steel alloy comprising about 2.5% to about 4% chromium, about 1.5% to less than 2% tungsten, about 0.1% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition, wherein said alloy is heated to an austenitizing temperature and then cooled to produce an austenite transformation product.
- 2. A steel alloy in accordance with claim 1 wherein said austenite transformation product comprises a carbide-free acicular bainite.
- 3. A steel alloy in accordance with claim 1 further comprising up to about 0.25% tantalum.
- 4. A steel alloy in accordance with claim 1 further comprising up to about 1.5% molybdenum, where 2 [Mo]+[W]<3.5.
- 5. A steel alloy in accordance with claim 1 further comprising up to about 2% nickel.
- 6. A steel alloy in accordance with claim 1 further comprising up to about 0.01% boron.
- 7. A steel alloy in accordance with claim 1 further comprising up to about 1.5% manganese.
- 8. A steel alloy in accordance with claim 1 further comprising up to about 1% silicon.
- 10. A steel alloy in accordance with claim 1 further comprising up to about 0.2% hafnium.
- 11. A steel alloy in accordance with claim 1 further comprising up to about 0.2% zirconium.
- 12. A steel alloy in accordance with claim 1 further comprising up to about 0.25% niobium.
- 13. A steel alloy in accordance with claim 1 further comprising up to about 0.25% copper.
- 14. A steel alloy in accordance with claim 1 further comprising up to about 0.2% titanium.
- 15. A steel alloy in accordance with claim 1 further comprising 3% Cr, 1.5 to 3% W, 0.0 to 1.5% Mo, 0.0 to 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.1% C.
- 16. A high-strength, high-toughness steel alloy comprising about 2.5% to about 4% chromium, about 1.5% to about 3.5% tungsten, greater than 0.3% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition, wherein said alloy is heated to an austenitizing temperature and then cooled to produce an austenite transformation product.
- 17. A steel alloy in accordance with claim 16 wherein said austenite transformation product comprises a carbide-free acicular bainite.
- 18. A steel alloy in accordance with claim 16 further comprising up to about 0.25% tantalum.
- 19. A steel alloy in accordance with claim 16 further comprising up to about 1.5% molybdenum, where 2 [Mo]+[W]<3.5.
- 20. A steel alloy in accordance with claim 16 further comprising up to about 2% nickel.
- 21. A steel alloy in accordance with claim 16 further comprising up to about 0.01% boron.
- 22. A steel alloy in accordance with claim 16 further comprising up to about 1.5% manganese.
- 23. A steel alloy in accordance with claim 16 further comprising up to about 1% silicon.
- 24. A steel alloy in accordance with claim 16 further comprising up to about 0.08% nitrogen.
- 25. A steel alloy in accordance with claim 16 further comprising up to about 0.2% hafnium.
- 26. A steel alloy in accordance with claim 16 further comprising up to about 0.2% zirconium.
- 27. A steel alloy in accordance with claim 16 further comprising up to about 0.25% niobium.
- 28. A steel alloy in accordance with claim 16 further comprising up to about 0.25% copper.
- 29. A steel alloy in accordance with claim 16 further comprising up to about 0.2% titanium.
- 30. A steel alloy in accordance with claim 16 further comprising 3% Cr, 1.5 to 3% W, 0.0 to 1.5% Mo, 0.0 to 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.1% C.
- 31. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said steel alloy is formed into an article.
- 32. A steel alloy in accordance with claim 31 wherein said article comprises at least one of the group consisting of heat exchange equipment, column, tower, tank, storage vessel, pressure equipment, pressure vessel, reactor, equipment for metals production, piping, tubing, valve, valve component, expansion joint, and welding material.
- 33. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said article requires no tempering treatment after being air cooled from the austenitizing temperature.
- 34. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said article requires no tempering treatment after being quenched in a liquid from the austenitizing temperature.
- 35. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said article requires no heat treatment prior to being welded.
- 36. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said article requires no heat treatment after being welded.
- 37. A steel alloy in accordance with any one of claims 1-30, inclusive, wherein said article requires no heat treatment after fabrication thereof.
- 38. A method of producing a high-strength, high-toughness steel composition comprising the steps of:
a. forming a body of a ferritic steel composition comprising about 2.5% to about 4% chromium, about 1.5% to less than 2% tungsten, about 0.1% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition; b. heating said composition to an austenitizing temperature for a predetermined length of time; and c. cooling said composition from the austenitizing temperature at a rate to form an austenite transformation microstructure.
- 39. A method in accordance with claim 38 wherein said austenite transformation microstructure comprises a carbide-free acicular bainite microstructure.
- 40. A method in accordance with claim 38 wherein said austenitizing temperature is at least 1250° C. and said austenitizing time is at least 0.25 hour.
- 41. A method in accordance with claim 38 wherein said heating step further comprises heating the body in a medium selected from the group consisting of air, vacuum, and an inert atmosphere such as argon or helium.
- 42. A method in accordance with claim 38 wherein said heating step further comprises air cooling said body after heating.
- 43. A method in accordance with claim 38 wherein said cooling step comprises quenching said body in a liquid after heating.
- 44. A method in accordance with claim 38 wherein said cooling step further comprises cooling said composition from the austenitization temperature.
- 45. A method in accordance with claim 38 further comprising the step of tempering said body after cooling.
- 46. A method in accordance with claim 38 further comprising tempering said body after cooling at a temperature of less than or equal to about 780° C. for a time of up to 1 hour per inch of thickness of said body.
- 47. A method in accordance with claim 38 wherein the composition includes 3% Cr, 3% W, 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.5-0.15% C.
- 48. A method in accordance with claim 38 wherein the composition includes 3% Cr, 1.5 to 3% W, 0.0-0.75% Mo, 0.2 wt % to 1.0wt % Si, 0.2 wt % to 1.5 wt % Mn, 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.1% C.
- 49. A method in accordance with claim 38 further comprising increasing the hardenability of the composition by adding a minor alloying element selected from the group consisting of boron, titanium, tantalum, nickel, manganese, molybdenum, niobium, silicon, nitrogen, and copper.
- 50. A method of producing a high-strength high-toughness steel composition comprising the steps of:
a. forming a body of a ferritic steel composition comprising about 2.5% to about 4% chromium, about 1.5% to about 3.5% tungsten, greater than 0.3% to about 0.5% vanadium, and about 0.05% to 0.25% carbon with the balance iron, wherein the percentages are by total weight of the composition; b. heating said composition to an austenitizing temperature for a predetermined length of time; and c. cooling said composition from the austenitizing temperature at a rate to form an austenite transformation microstructure.
- 51. A method in accordance with claim 50 wherein said austenite transformation microstructure comprises a carbide-free acicular bainite microstructure.
- 52. A method in accordance with claim 50 wherein said austenitizing temperature is at least 1250° C. and said austenitizing time is at least 0.25 hour.
- 53. A method in accordance with claim 50 wherein said heating step further comprises heating the body in a medium selected from the group consisting of air, vacuum, and an inert atmosphere such as argon or helium.
- 54. A method in accordance with claim 50 wherein said cooling step further comprises air cooling said body after heating.
- 55. A method in accordance with claim 50 wherein said cooling step comprises quenching said body in a liquid after heating.
- 56. A method in accordance with claim 50 wherein said austenitizing step further comprises cooling said composition from the austenitization temperature.
- 57. A method in accordance with claim 50 further comprising the step of tempering said body after cooling.
- 58. A method in accordance with claim 50 further comprising tempering said body after cooling at a temperature of less than or equal to about 780° C. for a time of up to 1 hour per inch of thickness of said body.
- 59. A method in accordance with claim 50 wherein the composition includes 3% Cr, 3% W, 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.5-0.15% C.
- 60. A method in accordance with claim 50 wherein the composition includes 3% Cr, 1.5 to 3% W, 0.0-0.75% Mo, 0.2 wt % to 1.0 wt % Si, 0.2 wt % to 1.5 wt % Mn, 0.25% V, 0.0% to 0.25% Ta, 0.0 to 0.01% B, and 0.1% C.
- 61. A method in accordance with claim 50 further comprising increasing the hardenability of the composition by adding a minor alloying element selected from the group consisting of boron, titanium, tantalum, nickel, manganese, molybdenum, niobium, silicon, nitrogen, and copper.
- 62. A method of producing a high-strength, high-toughness steel alloy comprising the steps of:
a. forming a body of a ferritic steel composition comprising 2.5% to 4.0% chromium, 1.5% to less than 2% tungsten, 0.0% to 1.5% molybdenum, 0.10% to 0.5% vanadium, 0.2% to 1.0% silicon, 0.2% to 1.5% manganese, 0.0% to 2.0% nickel, 0.0% to 0.25% tantalum, 0.05% to 0.25% carbon, 0.0% to 0.01% boron, 0.0% to 0.2% titanium, 0.05% to 0.25% Nb, 0.0% to 0.08 % nitrogen, 0.0% to 0.2% Hf, 0.0% to 0.2% Zr, and 0.0% to 0.25% Cu, with the balance iron, wherein the percentages are by total weight of the composition; b. heating said composition to an austenitizing temperature for a predetermined length of time; and c. cooling said composition at a rate to form a carbide-free acicular bainite microstructure.
- 63. The method of claim 62 further comprising the additional step of:
d. tempering said composition at a temperature of not more than about 780° C. for a time of up to 1 hour per inch of thickness of said composition.
- 64. The method of claim 62, wherein said cooling step comprises air cooling said composition.
- 65. The method of claim 62, wherein said cooling step comprises quenching said composition.
- 66. A high-strength, high-toughness ferritic steel article made according to the method of claim 62.
- 67. A method of producing a high-strength, high-toughness ferritic steel alloy comprising the steps of:
a. forming a body of a ferritic steel composition comprising 2.5% to 4.0% chromium, 1.5% to 3.5% tungsten, 0.0% to 1.5% molybdenum, greater than 0.3% to 0.5% vanadium, 0.2% to 1.0% silicon, 0.2% to 1.5% manganese, 0.0% to 2.0% nickel, 0.0% to 0.25% tantalum, 0.05% to 0.25% carbon, 0.0% to 0.01% boron, 0.0% to 0.2% titanium, 0.05% to 0.25% Nb, 0.0% to 0.08% nitrogen, 0.0% to 0.2% Hf, 0.0% to 0.2% Zr, and 0.0% to 0.25% Cu, with the balance iron, wherein the percentages are by total weight of the composition; b. heating said composition to an austenitizing temperature for a predetermined length of time; c. cooling said composition at a rate to form a carbide-free acicular bainite microstructure; and
- 68. The method of claim 67 further comprising the additional step of:
d. tempering said composition at a temperature of not more than about 780° C. for a time of up to 1 hour per inch of thickness of said composition.
- 69. The method of claim 67, wherein said cooling step comprises air cooling said composition.
- 70. The method of claim 67, wherein said cooling step comprises quenching said composition.
- 71. A high-strength, high-toughness ferritic steel article made according to the method of claim 67.
Government Interests
[0001] The United States Government has rights in this invention pursuant to contract no. DE-AC05-000R22725 between the United States Department of Energy and UT-Battelle, LLC.