Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

Definitions

• the steel essentially consists of about 11.5% to 13.5% chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, carbon not over 0.05%, manganese not over 0.50%, silicon not over 0.60%, sulphur less than 0.015%, nitrogen not over 0.05%, and remainder essentially iron.
• the present invention is concerned with the precipitation-hardenable chromium-nickel-aluminum stainless steels and with various products and articles fashioned of the same, in a measure being a specific improved embodiment of the steels generally described in the copending application of D Cameron Perry, coapplicant herein, Ser. No. 227,731, filed Oct. 2, 1962 and entitled Chromium- Nickel-tAluminum Steel and Method, now abandoned in favor of the continuation-in-part application Ser. No. 334,923, filed Dec. 3, 1963 and entitled Chromium-Nickel- Aluminum Steel and Method.
• One of the objects of our invention is the provision of a chromium-nickel-aluminum stainless steel which may be formed or fabricated in a solution-treated condition by a variety of mechanical working and forming operations; which readily lends itself to brazing and welding in such condition; which is easily hardened by precipitation-hardening treatment at modest temperatures; and which in hardened condition is strong and yet tough and ductile, with substantial ductility even in large sections.
• Another object is the provision of a precipitation-hardenable chromium-nickel-aluminum stainless steel which is martensitic in the annealed or solution-treated condition; which lends itself to the production of bars, rods, wire and the like in that condition; and which, moreover, may then be converted by hot or cold-working into plate, sheet, strip and the like, as Well as drawn rods, wire and other products which are precipitation-hardenable from a solution-treated martensitic condition either by single treatment at modest hardening temperatures or by double heat-treatment as desired, depending upon the precipitation-hardening treatment required by other metals with which our steel is associated.
• a further object is the provision of particular articles of manufacture comprising the martensitic steel and products of our invention which, following manufacture by mechanical working, forming, shaping and the like and/ or by brazing, welding or the like, are precipitation-hardenable by heat-treatment by single treatment, that is, by merely heating from the solution-treated martensitic condition, where desired, or by double treatment as by heating at a transformation temperature and then reheating at precipitation-hardening temperatures without adverse effect upon properties, the particular precipitation-hardening treatment employed being dictated by time and equipment, or by the requirements of other metal included in the construction of the articles of manufacture under consideration.
• Our invention accordingly, consists of the combination of ingredients employed in our steel, in the correlation of these various ingredients, in the temperatures and cycles of heat-treatment employed in connection with our steels, and in the articles and products fashioned thereof, all as more particularly described herein, the scope of the application of which is more fully set forth in the claims at the end of this specification.
• the choice of a further precipitation-hardenable steel, where greater strength or greater ductility is required of one or more of the component portions, is limited by the hardening characteristics of the principal precipitation-hardening metals employed.
• a chromium-nickel-aluminum stainless steel which readily lends itself to the production of a variety of rolled or drawn products such as plate, sheet, strip, billets, bars, rods, wire and the like, which products in solution treated or annealed condition may be fabricated into a variety of articles of ultimate use or composite parts thereof, by various mechanical operations, and by brazing, welding and the like; which steel and articles fashioned thereof are precipitation-hardenable from the annealed or solution-treated condition either by single treatment or by double treatment, as desired, or as depending upon the hardening characteristics of other precipitation-hardening metals employed in the construction of said articles, all to achieve great strength toegther with good ductility and toughness.
• a chromium-nickel-aluminum stainless steel of critical composition in terms of the ingredients chromium, nickel and aluminum, which additionally essentially contains a critical amount of the ingredient molybdenum.
• the steel of our invention essentially consists of about 11.5% to 13.5% chromium, about 7.0% to 9.0% nickel, or even to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, and the remainder essentially iron.
• the ingredients carbon, manganese, silicon, phosphorus, sulphur and nitrogen, which commonly are present, are maintained in low amount.
• the carbon is not over 0.05%, the manganese not over 0.50%, the silicon not over 0.60%, the phosphorus 0.040% max., and usually not over 0.015%, the sulphur 0.020% max., and preferably not over 0.010%, and the nitrogen preferably not over 0.05
• Titanium in amounts up to about 0.10% may be added Where desired; more especially, titanium in amounts up to about 0.50% and/or columbium in amounts up to 0.75% may be added.
• a carbon content in excess of 0.05% causes a precipitation of carbides in heating with adverse effect upon ductility.
• a carbon content in excess of 0.02% preferably is employed for we find that with a lesser amount there is a tendency to build up ferrite.
• Manganese should not exceed 0.50% because of its ferrite-forming tendencies. At least 0.20%, however, is desired where oxides are inclined to be present in the metal, in order to assure cleanliness. When the steel is made by vacuum melting both manganese and silicon may be virtually eliminated.
• the sulphur content should not exceed 0.020% and preferably should not exceed 0.010%, as previously indicated, this in order to assure a steel of maximum toughness as pointed out hereinafter.
• the nitrogen content of the steel should not exceed 0.05 because a greater amount disturbs the structural balance with resultant loss in the ability of the metal to harden by single heat-treatment; preferably the nitrogen content is not over 0.01% as previously mentioned. At present this low value is best obtainable by vacuum melting or by degassing processes.
• a preferred steel according to our invention essentially consists of about 11.5 to 13% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2% to 2.5% molybdenum, and remainder essentially iron.
• Another preferred steel essentially consists of about 12.5% to 13.5% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2.0% to 2.5% molybdenum, and remainder essentially iron.
• a further preferred steel, this of restricted ferrite content essentially consists of about 11.5% to 12.5% chromium, about 7.0% to 9.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.5% molybdenum, and remainder essentially iron.
• the carbon content does not exceed about .04%, and preferably is .02% to .04%, the manganese content is up to about .50%, and the silicon content is up to about .50%.
• the sulphur content amounts to no more than .020% and in a preferred steel does not exceed about .0l5%.
• the nitrogen content is not over about 0.04%, preferably not over about 0.03%.
• the phosphorus content may amount to as much as 0.040%, although as previously indicated, it usually does not exceed 0.015%.
• the ingredients titanium and/ or columbium preferably are included in the composition of our steel, titanium where used being in amounts up to 0.50%, particularly 0.05% to 0.50%, and columbium where used being employed in amounts up to 0.75%, more particularly 0.10% to 0.50%.
• titanium-bearing and/ or columbiumbearing steels especially the latter, there is assured a freedom from intercrystalline or intergranular corrosion in the as-welded condition and in the welded and precipitation-hardened condition.
• the steel of our invention conveniently may be made in the electric arc furnace or in the induction furnace, these being referred to as air-melting or melting at atmospheric pressure.
• the steel may be vacuum-melted, as by melting in electric induction furnace under vacuum conditions. It also may be melted by Way of a double melting process, i.e., melted first in the electric arc furnace at atmospheric pressure, with the resultant heat of steel being cast in the form of electrodes which are then remelted under vacuum conditions.
• a further double melting process comprises first melting in the vacuuminduction furnace, with the resulting heat of steel being cast into consumable electrodes, which electrodes are then remelted under vacuum conditions.
• the steel had, by whatever melting process employed, is in the form of casting which are cast in the form of, or may be converted into, slabs, blooms and billets, and from these into hot-rolled plate, sheet, strip, bars, rods, wire, and like products.
• the metal works well in the mill.
• Our steel in the form of plate, sheet, strip, bars, rods, wire, or like converted products is supplied the customerfabricator in the hot-rolled and annealed condition. This contemplates heating at 1500 to 2100 F. and cooling. In this condition the steel is martensitic. The hardness is on the order of Rockwell C27-35.
• the annealing or solutiontreatment may be performed by the customer-fabricator, with heating at some 1500 to 2000 F. Usually a heating at about 1700 F., with time of heating depending upon thickness, is considered satisfactory. And with cooling to room temperature through quenching in either air, oil or water, the metal is workable and formable.
• the steel of our invention may be supplied in the form of forging billets or hot-rolled plate. Or it may be supplied in a cold-rolled condition, that is, in the form of cold-rolled and annealed sheet, strip, bars, rods, and the like. Or it may be supplied in the form of cold-drawn wire.
• the steel is in a martensitic condition with hardness of the cold-rolled or colddrawn metal on the order of Rockwell C35-40.
• the steel may be machined as by cutting, drilling, tapping and threading. And of particular consequence, the steel may be brazed or welded in the fabrication of a variety of articles of use, the steel forming the entire article, or a component part as desired.
• the metal is particularly suited to the production of supersonic aircraft parts, notably the ribs, stiffeners, stringers and like sections. Likewise, it is suited to the production of the skin sections or casings of planes, missiles, rockets, or the like. And to the production of high pressure vessels and tankage where there are encountered stresses along all three major axes.
• the steel of our invention is subjected to a precipitation-hardening or age-hardening treatment.
• a mere heating at a temperature of 900 to 1150 F. gives a desired hardening.
• the steel of our invention is a component part of an article, the other metals of which are in austenitic or semiaustenitic condition and are not directly amenable to hardening by a single heating
• the transformation treatment comprises a heating at 1300 to 1750 F. and then cooling to a temperature of between about 60 F. and -200 F. The durations of the heating and cooling are not critically important.
• brazing operation is employed in fabricating an article this may be viewed as a part of the heat-treatment by choosing a brazing alloy which has a flow point of about 1600 to 2000 F. and performing the brazing, preferably at a temperature of 1800 to 2000 F. Following brazing, the article is cooled to a temperature of about 1700 F. where it is held for about 30 minutes. This assures the greater toughness which results from heating the steel within the upper part of the 1300 to 1750 F. temperature range.
• the steel, however fabricated, is brought to final hardness by reheating at a temperature of some 900 to 1150 F. and cooling in air, oil or water. Usually, we find that reheating at 950 F. for an hour or more and quenching gives desired results. Here again, the hardness had is on the order of Rockwell C40-50.
• our steel is characterized by a combination of strength and ductility. Moreover, these properties are had in longitudinal direction, in short transverse direction and in long transverse direction. And in the preferred steel, that is, the steel of especially loW carbon, sulphur and nitrogen contents, the values of strength and ductility are about equally balanced along these three axes.
• the titaniumbearing and the columbium-bearing steels in hardened condition, following a welding or brazing operation, are particularly resistant to corrosion.
• the remainder of the composition is essentially iron, with the amount of nitrogen typically 0.03%.
• the steel of our invention possesses excellent stresscorrosion properties even in the presence of salt atmosphere. Samples of our steel were exposed directly to sea air at Kure Beach, North Carolina, in comparison with similar precipitation-hardened steel considered to possess TABLE II (b) [h'iechanical Properties of the Steels of Table 11(21) in Medium Section] Percent Percent U.T.S., 0.2% Y.S., El. in reduction Size Direction p.s.i. p.s.i. 2 inches area Heat No.:
• 1 BCHI 900 Heat to 1,675 F.-hold 15 mins.; cool to 1,000 F. in 30 mins., air cool to room temp.; minus 100 F. for 8 hrs., air warm; 900 F. for 8 hrs., air cool.
• the preferred steel is achieved through double vacuummelting, that is, melting to specification in the electric induction furnace under vacuum to form electrodes, and then remelting these electrodes under vacuum to achieve the finished metal.
• double vacuummelting that is, melting to specification in the electric induction furnace under vacuum to form electrodes, and then remelting these electrodes under vacuum to achieve the finished metal.
• a preferred steel of critically low manganese, silicon, 8 63 sulphur and nitrogen contents essentially consists of about 2 10 11.5% to 13.5% chromium, about 8.0% to 10.0% nickel, 1 00 about .5% to 1.5% aluminum, about 1.75% to 2.50% 0018 molybdenum, manganese not exceeding about .10% silicon not exceeding about .10% sulphur not exceeding Remainder of the composition is essentially iron.
• VGISQ. (z) do 224, 400 201, 600 13. 1 Double-treatment Short Transversal. 224, 600 203, 700 I 12.0 (2) o 224, 400 203,100 1 10. 0
• the mechanical properties of the steel of our invention differ somewhat with differences in temperature of final hardening. As best seen in Table IV(b) above, the tensile strength and the yield strength are inclined to fall off as the precipitation-hardening is increased from 950 F., to 1000 F., to 1050 F., and to 1100 F. As may be expected, there is corresponding increase in ductility. Surprisingly, there is had a great increase in impact strength, this latter increasing from the figure of 13 to 23 ft.-lbs. Charpy V-notch for the longitudinal samples with the steel hardened at 950 F., to some 46 to 53.5 ft.-lbs. for that hardened at 1000 F., to some 102 to ft.-lbs. for that hardened at 1050 F., and finally to a figure exceeding 120 ft.-lbs. on up to 149 ft.-lbs. for that hardened at 1100 F.
• the toughness of the steel of critically low manganese, silicon and sulphur contents is perhaps best illustrated in It is to be noted that the steel hardened by heating at 950 F. has an impact strength on the order of some 5 to 6 /2 ft.-lbs. with a W/A Factor of some 574 to 800 in. pounds per square inch, while that hardened at 1050 F. has an impact strength on the order of 57 /2 to 72 /2 ft.- lbs. with a W/A Factor of 7162 to 8600 in. pounds per square inch. The depth of the fatigue crack in all cases amounted to some 0.05 to 0.08 inch.
• the metal is supplied a customer-fabricator in the form of plate, sheet, strip, bar, Wire, rods and the like usually in the annealed or solution-treated condition. It may be machined as by cutting, drilling, tapping and threading. And it may be fabricated by Welding, brazing or other fabricating operations.
• the steel and fabricated articles are then hardened, as noted above, either by simple heating, or by transformation treatment and then heating at hardening temperature to give strength along with ductility and toughness. Strength and toughness are had in the direction of working as well as in the transverse directions.
• the steel of our invention is particularly suited to a variety of applications where stresses are encountered along all three axes. And it is suited to applications encountering corrosion even under stress; the stress-corrosion properties in severe salt atmosphere being surprisingly superior to one of the better known steels of the prior art.
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 11.5% to 13.5% chromium, about 7.0% to 10.0% nickel, about Longl 0017 6. 5 780' Intermediate 0677 6. 5 800 Short transverso 0498 5. 0 574 Intermediate 0498 6. 0 680 Longl 0782 57. 2 7. 380 Intermediate 0590 72. 5 8, 600
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 11.5% to 13.5% chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, carbon not exceeding 0.05 manganese not exceeding 0.50%, silicon not exceeding 0.60%, phosphorus not exceeding 0.040%, sulphur not exceeding 0.010%, nitrogen not exceeding 0.05%, and remainder essentially Iron.
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable there from both by single heat-treatment and by double heattreatment to give strength together with ductility, and essentially consisting of about 11.5% to 13.5% chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50 molybdenum, carbon exceeding 0.02% but not exceeding 0.05%, manganese not exceeding 0.40%, silicon not exceeding 0.50%, phosphorus not exceeding 0.040%, sulphur not exceeding 0.005%, nitrogen not exceeding 0.01%, and remainder essentially iron.
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 11.5% to 13.5% chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, up to about .05% carbon, manganese and silicon each not exceeding about .10%, sulphur and nitrogen each not exceeding about .005 and remainder essentially iron.
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 11.5% to 13% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2% to 2.5% molybdenum, up to about .05% carbon, up to about .50% manganese, up to about .50% silicon, sulphur less than .015 nitrogen up to about 0.05 and remainder essentially iron.
• a stainless steel which is martensitic in the solu tion-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 11.5% to 13% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2% to 2.5% molybdenum, about .02% to .04% carbon, up to about .50% manganese, up to about .50% silicon, up to about .010% sulphur, nitrogen up to about 0.04%, and remainder essentially iron.
• a stainless steel which is martensitic in the solution-treated condition and precipitation-hardenable therefrom both by single heat-treatment and by double heattreatment, and essentially consisting of about 12.5% to 13.5% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2.0% to 2.5 molybdenum, about 0.2% to .05% carbon, up to about .50% manganese, up to about .50% silicon, up to about 010% sulphur, nitrogen up to about 0.05%, and remainder essentially iron.
• a stainless steel which is martensitic in the solutiontreated condition and equally precipitation-hardenable therefrom both by single heat-treatment and by double heat-treatment, and essentially consisting of about 11.5 to 13.5% chromium, about 7.0% to 10.0% nickel, about .5% to 1.5% aluminum, about 1.75% to 2.5% molybdenum, carbon not exceeding about .05%, manganese not exceeding about .10%, silicon not exceeding about .l%, sulphur not exceeding about .015 nitrogen not exceeding about 010%, and remainder essentially iron.
• a stainless steel which is martensitic in the solutiontreated condition and equally precipitation-hardenable therefrom both by single heat-treatment and by double heat-treatment, and essentially consisting of about 11.5 to 13.5 chromium, about 7.0% to 10.0% nickel, about .5% to 1.5% aluminum, about 1.75% to 2.5% molybdenurn, carbon not exceeding about .04%, manganese not exceeding about .10%, silicon not exceeding about .10%, sulphur and nitrogen each not exceeding .005 and remainder essentially iron.
• Stainless steel which is martensitic in the solutiontreated condition and about equally precipitation-hardenable from such condition by single heat-treatment and by double heat-treatment to give great strength, and essentially consists of about 11.5 to 13.5 chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75 to 2.50% molybdenum, carbon not exceeding 0.05%, phosphorus not exceeding 0.040%, sulphur not exceeding 0.010%, nitrogen not exceeding 0.05%, and remainder essentially iron.
• a precipitation-hardenable composite article comprising stainless steel, martensitic in the solution-treated condition, and essentially consisting of about 11.5
• chromium about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenurn, carbon not exceeding 0.05 sulphur not exceeding 0.010%, nitrogen not exceeding 0.05%, and remainder essentially iron.
• a precipitation-hardenable composite fabricated article comprising stainless steel, martensitic in the solutiontreated condition, and essentially consisting of about 11.5% to 13% chromium, about 7.5% to 9.0% nickel, about 1% aluminum, about 2% to 2.5 molybdenum, up to about .05% carbon, up to about .50% manganese, up to about .50% silicon, sulphur not exceeding about .015%, nitrogen up to about 0.01%, and remainder essentially iron.
• a stainless steel, martensitic in the solution-treated condition and precipitation-hardenable from such condition essentially consisting of about 11.5 to 13.5 chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, carbon not exceeding 0.05 sulphur less than 0.015%, nitrogen not exceeding 0.05%, and remainder essentially 1mm.
• a stainless steel, martensitic in the solution-treated condition and precipitation-hardenable from such condition essentially consisting of about 11.5 to 13.5% chromium, about 7.0% to 10.0% nickel, about 0.5% to 1.5% aluminum, about 1.75% to 2.50% molybdenum, at least one of the group consisting of titanium in amounts up to 0.50% and columbium in amounts up to 0.75%, carbon not exceeding 0.05 sulphur less than 0.015%, nitrogen not exceeding 0.05 and remainder essentially iron.
• a stainless steel, martensitic in the solution-treated condition and precipitation-hardenable from such condition essentially consisting of about 11.5% to 13.5 chromium, about 7.0% to 10.0% nickel, about 0.5 to 1.5% aluminum, about 1.75% to 2.50% molybdenum, about 0.10% to 0.50% columbium, carbon not exceeding 0.05%, sulphur less than 0.015%, nitrogen not exceeding 0.05 and remainder essentially iron.

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• 1964
  • 1964-07-31 BE BE651249D patent/BE651249A/xx unknown
  • 1964-08-03 DE DE1458330A patent/DE1458330C3/de not_active Expired
  • 1964-08-04 GB GB31438/64A patent/GB1077979A/en not_active Expired
• 1966
  • 1966-10-10 US US585298A patent/US3556776A/en not_active Expired - Lifetime
• 1967
  • 1967-04-24 BE BE697441D patent/BE697441A/xx unknown
  • 1967-06-30 SE SE10016/67*A patent/SE316023B/xx unknown
  • 1967-07-21 DE DE1608097A patent/DE1608097C3/de not_active Expired
  • 1967-09-01 GB GB40115/67A patent/GB1138098A/en not_active Expired

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