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
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
  • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni

Definitions

• the present invention relates to ferrous alloys and, more particularly, to ferrous-base alloys characterized by strength levels of a tremendously high order of magnitude, to wit, tensile strengths above about 300,000 pounds per square inch (p.s.i.) to about 500,000 p.s.i. and higher.
• p.s.i. pounds per square inch
• 500,000 p.s.i. p.s.i.
• the exceedingly high strengths manifested by alloys contemplated herein are obtained with the simplest of heat treatment. Recourse to costly and/or complicated processing techniques, including quenching, tempering, severe plastic deformation, e.g., ausforming, cold rolling, cold drawing, etc., is not at all necessary.
• the maraging steels have been deemed particularly attractive since a quenching operation is not required and, thus, the well documented problems, e.g., distortion, warpage, dimensional change, etc., attendant the high strength, quenched and tempered, carbon-containing, low alloy steels were obviated.
• temper embrittlement problems characteristic of the latter steels were also greatly minimized, if not completely eliminated.
• Such attributes of the maraging steels undoubtedly attest to their rather spontaneous commercial acceptance.
• due regard being given to the many virtues of known maraging steels we are unaware of any such maraging steel which manifests the capability of providing yield strengths of, say, 400,000 p.s.i. or 450,000 p.s.i.
• tensile strengths well above 300,000 p.s.i. and up to about 500,- 000 p.s.i. not only can be obtained but are achieved with the processing advantages attendant the maraging steels and without the disadvantages of the quenched and tempered or ausformed steels.
• the present invention is to be construed as excluding the application of any appropriate processing or treating operation, e.g., plastic deformation.
• Cold working for example, can be used to advantage; in fact, tensile strengths above 500,000 p.s.i. have been obtained in accordance herewith by cold reducing but a nominal amount, to wit, 20% to 30%. It is perhaps of some interest to note that plastically deforming by 30% is quite far removed from the percentage of plastic deformation reported in connection with the ausforming process wherein highest strength levels have been attained.
• alloys within the invention boost the strength levels of prior art maraging steels by upwards of 175,000 p.s.i. as to strength plus ductility and using corresponding periods of development, if, for example, a maraging steel affording a yield strength level of about 300,000 p.s.i. is used as a representative standard, the present invention encompasses alloys which boost the yield strength by a factor of at least about 75,000 p.s.i. to over 100,000 p.s.i.
• tensile ductility of from 50% to
• the present invention is not intended to be restricted to steels having a high degree of ductility.
• high strength or, for that matter, extreme hardness is of prime significance and a high degree of ductility is not of major importance, e.g., dies, bearings, machine tools, knives, razor blades, etc.
• compositions will provide these properties. Where high strengths on the order of 400,000 p.s.i., e.g., 375,000 to about 425,000 p.s.i. and advantageously up to 450,000 p.s.i., are required together with a good level of ductility, this need is also satisfied in accordance herewith. Higher levels of ductility can be obtained where magnitudes of strength of about 350,000 to 375,000 p.s.i. are satisfactory.
• Another object of the invention is to provide ferrous alloys which manifest exceptionally high strength, e.g., 400,000 to 425,000 or 450,000 p.s.i., and which are duetile at such strength levels.
• the invention further contemplates providing ferrous alloys which are extremely hard.
• the present invention contemplates ferrous alloys containing, by weight, from 5% to 16.5% nickel, e.g., 7% to nickel, about 7% to 16% molybdenum, e.g., 8% to 15% molybdenum, about 8% to 30% cobalt, e.g., 10% to 25% cobalt, the sum of the molybdenum plus cobalt being at least about 20% and advantageously at least about 22%, up to 2.5% titanium, up to 2.5 aluminum with the sum of the titanium plus aluminum not exceeding about 3%, and advantageously not exceeding 2.5%, up to 0.3% carbon, the balance of the alloys being essentially iron.
• balance or balance essentially when used in referring to the amount of iron in the alloys does not exclude the presence of other elements commonly present as incidental elements, e.g., deoxidizing and cleansing elements, and impurities ordinarily associated therewith in small amounts which do not materially affect the basic characteristics of the alloys.
• elements such as sulfur, phosphorus, hydrogen, oxygen, nitrogen and the like should be maintained at low levels consistent with commercial practice.
• supplementary elements can be present in the alloys as follows: up to 2% columbium, e.g., up to 1.5%; up to 4% tantalum, e.g., up to 3%; up to 0.1% boron, e.g., up to 0.05%; up to 0.25% zirconium, e.g., up to 0.15%; up to 8% chromium, e.g., up to 5%; up to 2% vanadium, e.g., up to 1.5%; up to 0.5% silicon and advantageously not more than 0.25%; up to 0.5% manganese and advantageously not more than 0.25%; up to 0.1% calcium, e.g., up to 0.075%; up to 1% beryllium, e.g., up to 0.5%; and up to 4% copper, e.g., up to 2%.
• columbium e.g., up to 1.5%
• up to 4% tantalum e.g., up to 3%
• the respective amounts of the aforementioned supplementary elements be as follows: up to 1% columbium, e.g., 0.01% to 0.5%; up to 2% tantalum, e.g., 0.01% to 0.5%; up to 0.01% boron, e.g., 0.0005% to 0.0075%; up to 01% zirconium, e.g., 0.001% to 0.1%; up to 4% chromium, e.g., 0.1% to 3.5%; up to 1% vanadium, e.g., 0.1% to 0.5%; up to 0.15% silicon, e.g., 0.01% to 01%; up to 0.15% manganese, e.g., 0.01% to 0.1%; up to 0.05% calcium, up to 0.1% beryllium, and up to 1% copper.
• the total sum of the supplementary elements should not exceed 10% and advantageously should not exceed 6%.
• Tungsten can be used to replace molybdenum in part on an atom for atom basis, two parts of tungsten by weight for one part of molybdenum, in an amount up to 8% by weight.
• the tungsten not exceed 6% and preferably should not exceed 4% particularly since molybdenum, in contrast to tungsten, importantly contributes to improved forgeability and/or hot workability and also imparts enhanced ductility characteristics.
• the element nickel contributes, among other things, to achieving ductility, toughness and a desired martensitic structure upon cooling from hot working or, where used, solution treatment.
• the subject alloys are austenitic at high temperature and undergo transformation during cooling.
• Austenite reversion can be minimized by using low aging temperatures, e.g., below 700 F., but this, in turn, would significantly impair the strength level of the steels.
• the nickel content is at a level as high as is consistent with providing the lowest M temperature together with freedom of substantial amounts of austenite, e.g., amounts of austenite on the order of above about 5%.
• austenite e.g., amounts of austenite on the order of above about 5%.
• low nickel contents invite the tendency for formation of ferrite or other undesirable and subversive phases and such phases can wreak havoc with various mechanical characteristics of the steels. Accordingly, it is advantageous that the nickel content be from 7% to 16.5% and where optimum toughness characteristics are desired, it is most preferred that the nickel content be at least 11%, e.g., 11% to 16%.
• Molybdenum and cobalt principally confer strengthening and hardening characteristics, the former being the more potent in this regard.
• Molybdenum as mentioned above herein, also provides, at high strength levels, good forgeability and ductility characteristics.
• the combined amounts of molybdenum and cobalt should be at least 20% and for best results the total content of these elements should be at least 22% and preferably at least 23%.
• it can be used in some measure in controlling the occurrence of transformation of austenite to ma-rtensite, depending, of course, upon a given nickel and molybdenum content.
• the cobalt content should not exceed about 22%. Further, provided that the molybdenum content is at least 11% and preferably at least 12%, the requirement that the sum of the molybdenum plus cobalt be at least 20% can be relaxed to the extent that the cobalt content can be lowered to 6%. In addition, it is preferred that the elements nickel, molybdenum and c balt be correlated such that the sum of the nickel plus the molybdenum plus one-tenth of the cobalt is not less than 16 and not greater than 27 and most advantageously not less than about 20 and not greater than 26.
• the maximum sum of the nickel plus molybdenum plus onetenth of the cobalt can be as high as about 30 or even higher but, in this connection, a cold treatment as by, for example, refrigeration and/ or cold working, may be necessary prior to aging to induce the desired degree of transformation to martensite.
• a cold treatment as by, for example, refrigeration and/ or cold working, may be necessary prior to aging to induce the desired degree of transformation to martensite.
• the important or essential point is that the alloys be in the martensitic or substantially martensitic condition prior to aging.
• Titanium and/ or aluminum serve to provide good deoxidation and malleabilization characteristics. Titanium, for example, serves to fix elements, such as oxygen, nitrogen and carbon. While the respective amounts of titanium or aluminum generally need not exceed about 1%, the total thereof not exceeding 1.5%, when molybdenum is present within the low side of the molybdenum range, e.g. 7% to 10%, titanium and/ or aluminum in an amount of 1%, e.g., 1.5%, to about 3% markedly serves to enhance the strengthening characteristics (as shown hereinafter), particularly in the presence of nickel at the higher end of the nickel range, e.g., 11% to 16% nickel.
• compositional ranges of alloys afford special properties, e.g., exceedingly high strengths and/or hardness, a high magnitude of strength plus good tensile ductility, etc.
• the alloy be of the following composition: about 7% to 13% nickel, about 12% to 15% molybdenum, about 12% to 22% cobalt, up to 1% titanium, up to 1% aluminum, up to 0.1% carbon with the balance essentially iron.
• such alloys should contain 7% to about 10.5% nickel, 12.5% to 14.5% molybdenum, about 14% to cobalt, up to 0.5 titanium, up to 0.5% aluminum, the sum of the titanium plus aluminum not exceeding 0.75%, up to 0.05% carbon and the balance essentially iron.
• the molybdenum content can be lowered to about 10%, i.e., 10% to 12%, provided the cobalt content is present in amounts of to Where a good combination of strength (375,000 p.s.i.
• the alloy should contain about 11% to 16% nickel, about 7.5% to 12% molybdenum, about 10% to 18% cobalt, the sum of the molybdenum plus cobalt being at least 22% and the balance essentially iron.
• the alloy should contain 12.5% to 15.5% nickel, 8% to 10.5% molybdenum, 12% to 16% cobalt, the sum of the molybdenum plus cobalt being at least 22%, up to 0.05% carbon, up to 0.5% titanium, up to 0.5% aluminum, the total titanium plus aluminum not exceeding 0.75%, with the balance being essentially iron. Should maximum hardness be the property of primary interest, the alloy should contain 5% to 10% nickel,
• air or vacuum melting practice can be utilized, preferably followed by consumable electrode melting for optimum efifects. It is advantageous to utilize materials of good purity to thereby minimize the occurrence of inclusions, contaminants, etc.
• the initially formed cast ingots should be thoroughly homogenized as, for example, by soaking, at a temperature of about 2200 F. to about 2300" F. for about one hour per inch of cross section. Thereafter, the alloys are hot worked (as by forging, pressing, rolling, etc.) and, if desired, cold worked to desired shape. A plurality of heating and hot working operations can be used and are advantageous to assure thorough homogenization of the cast structure through diffusion and to break up the cast structure.
• Hot working can be sati factorily carried out over a temperature range of 2300 F. or 2200 F. down to 1400 F., e.g., 2150 F. to 1500 F., with suitable finishing temperatures being about 2000 F. down to about 1500 F.
• Cooling from hot working is preferably accomplished by air cooling although furnace cooling, quenching, etc., can be employed.
• the steels can be directly aged (no other processing or heating step being necessary) by heating at a temperature of about 750 F. to 1100 F. for about hours to 0.1 hour, the longer aging periods being used in conjunction with the lower aging temperatures. Aging at 950 F. to 900 F. for about one to four hours has been found quite satisfactory. With aging times above about an hour or so, temperatures above about 1100 F. should not be used since deleterious austenite reversion can occur. On the other hand, temperatures appreciably below 750 F.
• the steels can be heated at a temperature as high as 1400 F., e.g., about 1200 F. to 1375 F. and preferably at 1250 F. to 1350 F., for a period of time of not greater than about 30 minutes, e.g., up to 15 minutes, the longer time being associated with the lower temperature.
• a period of from a few seconds, e.g., 15 seconds, up to five minutes is satisfactory for the temperature range of 1250 F. to 1350 F.
• the steels can be subjected to a solution annealing treatment prior to aging.
• the temperature extends over a range of about 1400 F. to about 2200" F.; however, the temperature used in dependent upon the molybdenum content to a considerable extent.
• a solution treatment temperature (if employed) of at least about 1400 F. should be used.
• solution treatment temperatures of at least about 1600 F., 1800 F., 1900 F., and 2000 F., respectively, should be employed. With lower temperatures, there is the risk of finishing the steels cold such that best results, notably strength, are not obtained.
• the steels were tensile strength) as a basic criterion in selection of a then hot worked and thereafter machined to specimens material for a given application. In accordance with the of about 0.135 to 0.14 inch in diameter.
• the steels were present invention the ratio of yield strength to ultimate then heat treated at about 900 F. for about 4 hours 10 tensile strength is advantageously at least 0.9 and higher, (Heat Treamtent A) or for five hours (Heat Treatment e.g., 0.95 and above. It is Worthy of mention to say that B) or at about 950 F. for about one hour (Heat Treatthe tensile ductility (4 x diameter) of various of the ment C).
• Heat Treatments A and C heretofore described, on occasion, other heat treatments were used as follows: aging for about 96 hours at about 800 F. (Heat Treatment D); refrigerating before aging at 900 F. for about four hours (Heat Treatment E).
• the alloys were prepared following the procedure used in connection with the alloys of Table I, except that the specimens were about 0.252 inch in diameter and in a few instances air melting practice was used. In addition to the alloying constituents and amounts thereof set forth in Table II, none of the alloys contained more than about 0.04% carbon nor more than about 0.15% of each of silicon and 441,000 p.s.i. The highest yield strength was 486,700 manganese.
• the data in Table II reflects that a markedly good combination of strength and tensile ductility can be obtained in accordance herewith. For example, at a yield strength of about 388,000 p.s.i., Alloy No. 26 manifested an exceptionally high tensile ductility of about 8% together with a reduction in area of about 38%. The data further illustrates the closeness between the yield and ultimate tensile strengths, the ratio therebetween being not less than 0.95% for any of Alloys Nos. 23 through 33.
• the alloys can contain 5% to 16.5% nickel, about 7% to 11% molybdenum, about 8% to about 30% cobalt, the sum of the molybdenum plus cobalt being at least 20%, at least one metal selected from the group consisting of up to 2.5% titanium and up to 2.5% aluminum, the sum of the titanium plus aluminum being at least 1% and not greater than 3%, up to 0.3% carbon, the balance being essentially iron.
• Such alloys contain 7% to 15% nickel, about 7% to 10% molybdenum, about 10% to 25% cobalt, at least one metal selected from the group consisting of up to 2.25% titanium and up to 2.25 aluminum, the sum of the titanium plus aluminum being at least 1.5% and not greater than 2.5%, up
• Alloys Nos. 34 through 42 exhibited extremely low hardness, hardness levels more than quite below that characteristic of the alloys contemplated herein.
• Microstructure studies of Alloys Nos. 34 through 40 revealed that only Alloy No. 34 was martensitic, Alloys Nos. 35 through 40 being austenitic and Alloy No. 37 being ferritic. All the alloys within the invention were martensitic and suflice to say the Rockwell hardnesses thereof were of a magnitude substantially higher than Alloys Nos. 34 to 42.
• alloys contemplated herein are also resistant to stress corrosion cracking.
• the alloys are useful in the production of such items as bar, rod, plate, castings, wire, etc., and products made therefrom, including fasteners, e.g., bolts;
• fasteners e.g., bolts;
• at least titanium and/or aluminum should be used in an amount of at least 0.05%, e.g., 0.1%. Desired shapes are best obtained prior to aging, i.e., in the hot worked or annealed condition since the alloys are comparatively soft and thus are more amenable to shaping operations such as cold working.
• aging temperatures from 850 F. to 950 F. are deemed the most satisfactory, the aging period not exceeding about ten hours.
• martensite or substantially martensite include the decomposition and/or transformation products of austenite obtained upon cooling from the hot working operation (or, where used, a solution annealing treatment). These terms also include transformation products of austenite resulting from the application of a cold treatment, e.g., refrigeration at a temperature down to minus 300 F. and/ or cold working.
• a martensitic, iron-base alloy manifesting an exceptionally high combination of strength and ductility in the aged condition, said alloy consisting essentially of about 11% to about 16% nickel, about 7.5% to about 12% molybdenum, about to about 18% cobalt, the sum of the molybdenum plus cobalt being at least 20%, up to 0.1% carbon, up to 1% titanium, up to 1% aluminum, the sum of the titanium plus aluminum not exceeding 1.5%, and the balance essentially iron.
• a martensitic, iron-base alloy manifesting an exceptionally high combination of strength and ductility in the aged condition, said alloy consisting essentially of 12.5% to 15.5% nickel, 8% to 10.5% molybdenum, 12% to 16% cobalt, up to 0.05% carbon, up to 0.5% titanium, up to 0.5% aluminum, the sum of the titanium plus aluminum not exceeding 0.75%, and the balance essentially iron.
• a martensitic, ferrous-base alloy characterized by a tensile strength of about 425,000 p.s.i. in the aged condition and being of a composition within the following ranges: about 7% to about 13% nickel, about 12% to about 15% molybdenum, about 12% to about 22% cobalt, up to about 0.1% carbon, up to about 1% titanium, up to about 1% aluminum, the sum of the titanium plus aluminum not exceeding about 1.5%, and the balance essentially iron.
• a martensitic, ferrous-base alloy characterized by a tensile strength of above about 425,000 p.s.i. in the aged condition and being of a composition within the following ranges: about 7.5% to about 10.5% nickel, about 12.5%
• molybdenum 12 to about 14.5% molybdenum, about 14% to about 20% cobalt, up to about 0.05% carbon, up to 0.5% titanium, up to 0.5% aluminum, the sum of the titanium plus aluminum not exceeding 0.75%, and the balance essentially iron.
• a martensitic, ferrous-base alloy characterized by a tensile strength of above about 425,000 p.s.i. in the aged condition, said alloy containing about 7% to 10% nickel, about 10% to 12% molybdenum, about 25% to 30% cobalt, up to 0.1% carbon, up to 1% titanium, up to 1% aluminum, the sum of the titanium plus aluminum not exceeding 1.5%, and the balance essentially iron.
• a martensitic, iron-base alloy characterized by a hardness of at least Rockwell C 60 in the aged condition and containing from 5% to about 10% nickel, from 13% to 16% molybdenum, from 16% to 30% cobalt, up to 0.1% carbon, up to 1% titanium, up to 1% aluminum, the sum of the titanium plus aluminum not exceeding 1.5 and the balance essentially iron.
• a martensitic, iron-base alloy characterized by a hardness of at least Rockwell C 60 in the aged condition and containing from 6% to 9% nickel, from 13.5% to 15.5% molybdenum, from 16% to 30% cobalt, up to 0.05% carbon, up to 0.75% titanium, up to 0.75% aluminum, the sum of the titanium plus aluminum not exceeding 1% and the balance essentially iron.
• An iron-base alloy consisting essentially of from 5% to about 16.5% nickel, about 7% to about 16% molybdenum, about 8% to about 30% cobalt, the sum of the molybdenum plus cobalt being at least about 20%, up to 2.5% titanium, up to 2.5 aluminum, the sum of the titanium plus aluminum not exceeding about 3%, up to 1% carbon, up to 2% columbium, up to 4% tantalum, up to 0.1% boron, up to 0.25% zirconium, up to 8% chromium, up to 2% vanadium, up to 0.5% silicon, up to 0.5% manganese, up to 1% beryllium, up to 4% copper, up to 0.1% calcium, the total amount of columbium, tantalum, boron, zirconium, chromium, vanadium, silicon, manganese, beryllium, copper and calcium being not more than 10%, and the balance essentially iron.
• a martensitic, iron-base alloy consisting essentially of from about 7% to about 15% nickel, about 8% to about 15% molybdenum, about 10% to about 25% cobalt ,the sum of the molybdenum plus cobalt being at least 22%, up to 2.5% titanium, up to 2.5% aluminum, the sum of the titanium plus aluminum not exceeding about 2.5%, up to 0.1% carbon, and the balance essentially iron.
• alloy as set forth in claim 20 wherein a total of not more than 6% of the following elements are present: up to 1.5% columbium, up to 3% tantalum, up to 0.05% boron, up to chromium, up to 1.5% vanadium, up to 0.15 zirconium, up to 0.25% silicon, up to 0.25% manganese, up to 0.5% beryllium, up to 2% copper and up to 0.1% calcium.
• a martensitic, iron-base alloy consisting essentially of from 5% to 16.5% nickel, from 7% to 11% molybdenum, from 8% to 30% cobalt, the sum of the molybdenum plus cobalt being at least 20%, up to 2.5% titanium, up to 2.5 aluminum, the sum of the titanium plus aluminum being not less than 1% nor greater than 3%, up to 0.3% carbon, up to 0.5% silicon, up to 0.5 manganese, and the balance essentially iron.
• a martensitic, iron-base alloy consisting essentially of from about 7% to about 15% nickel, about 7% to 10% molybdenum, about 10% to 25% cobalt, the sum of the molybdenum plus cobalt being at least 22%, up to 2.25% titanium, up to 2.25 aluminum, the sum of the titanium plus aluminum being not less than 1.5% nor greater than 2.5%, up to 0.1% carbon, up to 0.5% silicon, up to 0.5 manganese, and the balance essentially iron.
• a martensitic, iron-base alloy consisting essentially of from 5% to 16.5% nickel, about 11% to 16% molybdenum, about 6% to 30% cobalt, up to 0.3% carbon, up to 1% titanium, up to 1% aluminum, the sum of the titanium plus aluminum not exceeding 1.5 and the balance essentially iron.

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• 1965
  • 1965-05-20 US US457494A patent/US3359094A/en not_active Expired - Lifetime
• 1966
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