EP0477363A1 - Alliages thermo-resistants - Google Patents

Alliages thermo-resistants

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Publication number
EP0477363A1
EP0477363A1 EP91911033A EP91911033A EP0477363A1 EP 0477363 A1 EP0477363 A1 EP 0477363A1 EP 91911033 A EP91911033 A EP 91911033A EP 91911033 A EP91911033 A EP 91911033A EP 0477363 A1 EP0477363 A1 EP 0477363A1
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EP
European Patent Office
Prior art keywords
alloys
alloy
rare earth
tungsten
titanium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP91911033A
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German (de)
English (en)
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EP0477363A4 (en
Inventor
John H. Culling
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Carondelet Foundry Co
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Carondelet Foundry Co
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Publication date
Application filed by Carondelet Foundry Co filed Critical Carondelet Foundry Co
Publication of EP0477363A1 publication Critical patent/EP0477363A1/fr
Publication of EP0477363A4 publication Critical patent/EP0477363A4/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • 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

Definitions

  • Parts for industrial furnaces and similar installations need to be made from alloys of moderate cost yet require one or more of the properties of resistance to hot gas corrosion, carburization, thermal fatigue or thermal shock failure, along with hot strength and the capability of being melted and poured in air.
  • These parts have mostly been produced from alloy compositions standardized by the Alloy Castings Institute (ACI) Division of the Steel Founders Society of America and designated by an H followed by one other letter to differentiate between types.
  • ACI Alloy Castings Institute
  • H Alloy Castings Institute
  • the most widely employed of these ACI alloys have been the HH type with nominal contents of about 25% Cr and 12% Ni and the HK type, nominally containing about 25% Cr and 20% Ni.
  • the HT type When rapid or repeated thermal cycling was to be encountered in service, the HT type of about 35% Ni and 16% Cr was often employed.
  • Most of the other ACI-type alloys have been very much less employed.
  • ACI-type alloys have only moderate hot strength, but type HP, of about 35% Ni and 25% Cr content, combines good hot gas corrosion resistance with greater hot strength than any of the other ACI-types. Still, there have been ever increasing needs for alloys of even greater hot strength, and, in some instances, for further improvement in hot gas corrosion resistance or carburization resistance.
  • ACI-type alloys have been type HP, which has been altered by additions of about 1% to 5% W, and sometimes increases in nickel content up to about 48%, alternatively with about 15% Co, yielding a nickel plus cobalt content of about 48%.
  • Some modifications employ increased chromium content to about 28%, while other modifications also employ one or more of each of columbium, molybdenum or titanium in amounts of about 2% or less.
  • alloys containing nickel plus cobalt in amounts up to a total of 48% along with about 5% W suffer from a significant increase in cost.
  • Post, et al, U.S. Pat. No. 2,553,330 discloses improvements in the hot workability of virtually all corrosion and heat resistant alloys by the addition of about 8 to 12 pounds per ton of molten metal of cerium, lanthanum or other rare earth elements. Since these elements float on the surface of the molten bath and readily oxidize in air. Post's additions were said to result in recoveries in the final solid metal of only about 0.04% to about 0.12% by weight of rare earth elements. Post also teaches that recovery of substantially larger amounts of cerium and other rare earth metals results in deterioration in fabricability to levels below those of the original alloys without any rare earth metal addition.
  • Scharfstein, U.S. Pat. No. 3,168,397 claims benefits in corrosion resistant alloys by the addition of about 0.1% to about 0.3% of rare earth elements to the final metal.
  • Japanese patent J6 0059-051A describes what is essentially the ACI HP alloy base plus 0.5 to 3% W, 0.2 to 0.8% Mo, 0.3 to 1.5% Cb, 0.04 to 0.5% Ti, 0.02 to 0.5% Al and small amounts of B and N.
  • An examplary alloy contains nominally 1% Cb, 1% W, 0.4% Mo, 0.15% T, 0.15% Al, 0.08% N and 0.002% B. This alloy is then subjected to "coating" under controlled conditions to diffuse large amounts of aluminum into the "skin" of the alloy. Typically, when ready to go into service, this alloy will contain from about 0.3% to about 0.8% Al within the first millimeter of surface depth and about 0.15% to about 0.4% Al in the layer from 1mm to 2mm depth.
  • the resultant alloy is said to have excellent resistance to heat and carburization. While the alloy in this patent is said to contain large quantities of molybdenum, tungsten, columbium and titanium without pronounced tendency to form other matrix phases that shorten service life, such amounts of these elements would be too much for the HF, HH, HI, HK and HL types of ACI alloys, all of which are only borderline stable, with their standard nickel and chromium contents, before any other ferrite-forming elements are added. Also this Japanese patent specifies additions of aluminum, another very strong ferritizing element which would further tend to destabilize these alloys having borderline stability.
  • nickel-base superalloys do not contain any appreciable quantities of carbon and derive their hot strength by formation of precipitates from the solid solution matrix of nickel-aluminum-titanium compounds, referred to as gamma-prime phase.
  • These alloys may contain up to 8% Al and up to 5% Ti. Since both of these elements are readily oxidized at molten alloy temperatures in air, all such alloys are produced in vacuum or some inert gas atmosphere.
  • these elements when these elements are present in sufficiently large amounts in aggregate they cause formation of such non-austenitic phases, either in production or in service, as alpha, delta, sigma, laves, mu or others, all of which lead to early loss of hot strength and failure in service.
  • Manganese and nitrogen have been employed, often as partial nickel substitutes in corrosion resistant alloys, which operate at or near room temperatures.
  • a high manganese content is generally detrimental to hot strength of heat resistant alloys, and manganese is limited to about 2% maximum as a deoxidizing component in ordinary steelmaking practice.
  • nitrogen has beneficial effects upon corrosion resistance in certain media, it is less beneficial than carbon in developing hot strength in heat resistant alloys. Since both nitrogen and carbon in large amounts reduce ductility and weldability, carbon is primarily chosen for strengthening corrosion resistant super alloys.
  • Chromium is required in ACI-type and similar alloys to provide resistance to oxidation in air or in other typical service atmospheres.
  • Nickel is of some benefit in this regard for most of the hot gases typically encountered, so that a somewhat lower chromium content may be tolerated in alloys of very high nickel content.
  • type HF alloy begins to scale badly above about 1650°F
  • type HT of higher nickel but slightly lower chromium content than type HF, resists scaling to about 1950°F.
  • nickel is much more expensive than chromium
  • alloys of high nickel content are nevertheless employed because of their increased hot strength. It is not cost effective to attempt to reduce chromium by increasing nickel in the desire for only better hot gas corrosion resistance.
  • the N-153 and N-155 alloys were of lower molybdenum, tungsten and columbium content, but the N-153 alloy still contained too much of these three elements, when coupled with the lower amounts of nickel and cobalt, to be stable over long periods of time even at the reduced chromuim level.
  • the N-155 alloy continued in use for decades for moderately low temperature service of about 1350°F or less, because it is metallurgically quite well balanced and stable.
  • the other elements found in the super alloys are present in various combinations of 0 to 68% Co, 0 to 78% Ni, 3 to 28% Cr, 0 to 17% Mo, 0 to 20% W, 0 to 6% Cb, 0 to 8% Al and 0 to 5% Ti. More recently Manoir Electroalloys Corporation has produced ACI-type HK and HP alloys, which evidence further improved hot strength as a result of additions of about 0.5% W, 0.25% Cb, 0.10% Ti and some addition of cerium or other rare earth element. These alloys are marketed under the trade names TMA 4700 and TMA 6300 for the improved HK and HP alloys, respectively.
  • a further object of the invention is to provide such alloys that have relatively high hot strength and long life in the structural parts of industrial furnaces and in similar installations in which such parts must also possess excellent resistance to hot gas corrosion and to failure by thermal fatigue.
  • Another object of the invention is the provision of such alloys, which, although they can be melted and cast in vacuum or inert gas atmospheres, can be readily produced by ordinary air melting and air casting techniques and equipment without metallurgical detriment.
  • a further object is to provide such alloys that are relatively low in cost because of their low total critical or strategic element content as compared either to aircraft gas turbine superalloys or to the highly alloyed prior art ACI-type alloys.
  • a still further object of the invention is to provide master alloys in which tungsten, columbium, titanium and zirconium and one or more of the elements of the rare earth group are all combined in the solid state in the proportions desired in the final heat resistant alloys, such that these master alloys, which are always denser than the molten base alloy, may be added to any suitable ACI-type or similar base alloy (i.e. alloys of C, Fe, Ni, Co and Cr plus any of the usual elements Mn, Si, P or S, and other impurities) along with the desired additional element molybdenum to produce the heat resistant alloys of the invention.
  • any suitable ACI-type or similar base alloy i.e. alloys of C, Fe, Ni, Co and Cr plus any of the usual elements Mn, Si, P or S, and other impurities
  • a further object of the invention is to provide master alloys that contain all of the desired alloying elements of the invention, including molybdenum, so that a single addition of such master alloys can be easily made to base alloys to produce heat resistant alloys of the invention.
  • Another object of the invention is to provide either of these types of master alloys which also contain up to about 58% by weight of nickel and/or of iron as partial diluents, and which still contain the other desired addition elements in the proportions desired in the final heat resistant alloys.
  • a further object of the invention is to provide such master alloys, whereby, upon their addition to base alloy, they carry all of the desired elements to the bottom of the molten bath, where they lie until dissolved in isolation from the air at the top surface of the bath.
  • the present invention is directed to air-meltable, air-castable, weldable, heat resistant alloys that exhibit high creep rupture strengths and high ductilities.
  • These alloys consist of, by weight, between about 8% and about 62% Ni, between about 12% and about 32% Cr, between about 0.2% and about 0.95% W, between about 0.05% and about 0.8% Zr, between about 0.05% and about 0.8% Mo, between about 0.05% and about 0.6% Cb, between about 0.05% and about 0.45% Ti and between about 0.04% and about 0.4% of a rare earth component, such as mischmetal, cerium, lanthanum, or of any combination of one or more rare earth elements, and the balance essentially iron.
  • the instant alloys can also contain up to about 3% Si, up to about 0.05% B, up to about 0.3% V, up to about 3% Mn, up to about 0.8% C, up to about 0.4% N and up to about 25% Co.
  • the ACI-type and similar alloys of this invention can generally be produced in ordinary air and derive their hot strengths primarily by formation of carbides, not gamma prime precipitates.
  • the present invention is also directed toward master alloys, or alloy concentrates, in which either tungsten or tungsten and molybdenum are combined with all of the light elements of the group, columbium, zirconium, titanium, and a rare earth component, in such proportions that will result in the same proportions by weight of these elements in the final heat resistant alloys.
  • the master alloys consist of, by weight, between about 24% and about 47% W, between about 10% and about 23% Cb, between about 10% and about 21% Mo, between about 9% and about 21% Zr, between about 8% and about 13% Ti, and bewteen about 5% and about 12% rare earth component.
  • Master alloys which are not formulated with the inclusion of molybdenum consist of, by weight, between about 30% and about 51% W, between about 13% and 27% Cb, between about 11% and about 25% Zr, between about 10% and about 15% Ti, and between about 7% and about 14% rare earth component.
  • the essential components of heat resistant alloys of the invention are:
  • the alloys of the invention will nominally contain up to about 0.8% by weight carbon.
  • the nitrogen content is ordinarily the amount absorbed from the air during melting and pouring. However, for sound castings, nitrogen must not exceed its solid solubility limit and is held to a maximum of about 0.4% in alloys of the invention.
  • the alloys of the invention may also contain:
  • Master alloys of the invention contain either all six of the essential components, W, Cb, Mo, Ti, Zr and a rare earth component or all but Mo, along with residuals.
  • the residuals may include those elements which are not harmful to the final alloys of the invention in the quantities encountered and which may be included by virtue of their possible presence in either relatively pure or somewhat diluted raw materials suitable for master alloy production. It would be unnecessary and more costly to attempt to produce such master alloys from completely pure raw materials.
  • the residuals that might thus be encountered would likely include several of the group, iron, nickel, chromium, cobalt, manganese, silicon, carbon, tantalum, sulfur, phosphorus, aluminum, calcium, magnesium, copper, vanadium, tin, lead, bismuth, barium, nitrogen, oxygen, thallium, tellurium, selenium, antimony and even a small amount of molybdenum in those master alloys in which the final molybdenum content is intended to be obtained by a separate source of molybdenum addition. Most of these elements might be present in quantities ranging from about a tenth of a percent of the master alloys compositions down to less than about five parts per million by weight.
  • alloy concentrates of the invention consist of, by weightpercentages, the proportions as given in Tables A and B. TABLE A COMPOSITION OF MASTER ALLOYS - LOW RESIDUALS
  • Table B sets forth the broad ranges, by weight, of essential components in the master alloys which, for cost or convenience reasons, might include up to about half of their contents in iron, nickel and other residuals.
  • master alloys it is not desirable for master alloys to be formulated so as to include substantially greater than half of their contents as residuals because of such practical considerations as temperature drop of the molten bath when huge cold additions are made near the end of the melting process. Also, larger quantities of residuals tend to complicate the charge making process in some of the variations of ACI H-type alloys or of similar alloys. However, it would be quite practical to produce master alloys in which the residuals would total somewhat more than 3% to 5% but a lot less than 58%. In such cases, the master alloys would obviously contain the essential components in ranges proportionately spaced in between the extremes given in Tables A and B.
  • preferred master alloys consist of, by weight.
  • the master alloys of the invention will have densities at room temperature of at least about 8.1 gm/cc.
  • the range of densities of the master alloys set forth in Tables A to D are noted in those Tables. Therefore these master alloys, when added to a molten base alloy, carry all of the light, easily oxidizable, elements to the bottom of the molten bath where they remain in isolation from the oxygen in the atmosphere until dissolved. In this system of addition, the losses of the light elements during air melting are negligible.
  • the heat resistant alloys of the invention can be prepared without the use of master alloys, they are more easily and cheaply prepared through use of the instant master alloys.
  • microalloy elements and of their amounts for use in the heat resistant alloys of this invention is dependent upon many metallurgical factors, and deviations from the choice of a particular element and/or the amount employed may detrimentally influence the properties of the final alloys.
  • metals in heat service may fail as a result of low temperature behavior or of high temperature behavior.
  • Low temperature behavior is characterized by transcrystalline failure, high strain rates and low diffusion rate, and failure may be caused by thermal shock.
  • High temperature behavior involves intercrystalline failure, low strain rates and high diffusion rates, and failure may be caused by thermal fatigue.
  • the grain is the limiting strength component whereas the grain boundary is the weak component at lower stresses and higher temperatures.
  • titanium and columbium form carbides primarily within the metallic grains.
  • Zirconium is also a carbide former, but its most important effects are at the grain boundaries, where it increases the boundary ductility and tends to fill lattice discontinuities.
  • molybdenum increases stress carrying capacity at lower temperatures and over the shorter term, whereas tungsten increases higher temperature stress carrying capacity over the longer term.
  • molybdenum, cobalt and titanium in the amounts present in the invention, opposes failure by low temperature behavior, while the combination of -.ungsten, columbium and zirconium opposes failure by high temperature behavior.
  • Titanium on the other hand forms its own carbides which are very fine and slow to change. Columbium also tends to form its own carbides as well as to enter into titanium and zirconium cabides when titanium and zirconium are present, and further retards the rate of change of the resulting carbides.
  • the primary role of the rare earth component is, for example, to refine the grain, increase workability and retard hot gas corrosion. Thus all of the microalloys of the present invention act together in filling different roles.
  • the various elements of the invention have their mutual roles in reducing corrosion as well as improving hot strength.
  • Titanium 0.05%-0.45% 0.08%-0.30% 0.08%-0.20%
  • the present invention provides for the addition of elements from the above list, as discussed above, which, when combined in the correct proportions and quantities, and employed in ACI-type and similar alloy bases, produces higher hot strengths over longer periods of time in such alloys than any prior art modification of such alloys. Nevertheless, the alloys of the invention maintain excellent weldability, machinability, ductility and resistance to thermal shock or thermal fatigue failures as well as to oxidation or other hot gas corrosion.
  • the quantities and proportions of such elements employed in the instant alloys are such that they do not damage the austenitic matrices by destabilizing them in service and thereby causing early loss of properties. Further, the present invention accomplishes these results with such small quantities of relatively non-critical elements that the final cost of producing the alloys of the invention is only slightly increased above the cost of the base alloys themselves.
  • Master alloys of the invention may be prepared by combining all of the elements of Table II except molybdenum or all six of the elements listed. In either event the elements will be present in the proportions given in Table II, optionally containing, as diluent elements, iron, nickel and/or chromium (all of which are present in the alloys of the invention) in a total amount that comprises up to about half or less of the total weight of the essential elements. In all instances, whether such master alloys are comprised of only the essential elements plus trace amounts of other impurities or of those elements in the same proportions but diluted by up to their total weight by the diluent elements referred to, the resultant master alloys have a higher denisty than the molten alloy bases to which they are to be added. Also, it is generally easier and less costly to prepare master alloys where it is permissible, as in the present invention, to include modest amounts of impurities (such as, Al, Ca, Mg, Cu, Ba, Co, V, S, and P) .
  • the resultant master alloy will still sink to the bottom of the melt until dissolved, and the molybdenum addition may be made separately as metallic or as a molybdic oxide form or some other form since the oxide of molybdenum is not stable at melt temperatures and reverts to the metallic form and is dissolved in the melt without significant loss.
  • Master alloys containing iron, nickel and/or chromuim could, for instance, be composed by weight of approximately 20%W, 8% Mo, 10% Cb, 5% of each of Ti and Zr, 4% of a rare earth component and 48% Fe.
  • Another example might be a master alloy of about 22% W, 11% Cb, 6% Ti, 6% Zr and 5% of a rare earth component and 50% Ni.
  • the five primary or essential elements would be in the correct proportions of these elements in the final production alloy. Included as permissible impurities in the master alloys of the invention are small quantities of manganese, silicon and aluminum, in as much as all three of these elements are normal deoxidizing agents employed in common steel making practice.
  • the silicon and aluminum content must be kept to low proportions in the master alloy, since they are both of very low density and would defeat the purpose of the master alloy if present in such sufficient quantities as to reduce the master alloy density to the point that pieces or grains of it would no longer sink to the bottom of the molten alloys.
  • Manganese presents less of a problem of this nature because its density is closer to those of iron, nickel and chromium.
  • the manganese content of the master alloy should not be so high that it comes close to the desired amount in the final melt, because this presents steelmaking problems in certain air melting procedures and because some manganese will normally be present in various scraps and other melting components.
  • the master alloy contain no more than about 10% Mn, no more than about 8% Si and no more than about 4% Al. It is preferable that these elements would be present in lesser amounts in each instance, for example, on the order of 1% or less of each, but the essential characteristics of the master alloy are its density greater than about 8.1 gm/cc and its content of the five or six essential elements of the invention in correct proportions to each other as desired in the final alloys.
  • rhenium is about as scarce as platinum and therefore not practical for this invention even as a fraction of a per cent addition.
  • Hafnium is somewhat similar in lack of general availability, and theoretical considerations strongly suggest that it would behave somewhat like zirconium.
  • Tantalum which is also moderately scarce and expensive, behaves in the instant alloys like columbium but is required in twice the quantities of columbium due to its higher atomic weight.
  • Beryllium is extremely toxic as a solid element, a compound or a vapor, and not safe for ordinary foundry production methods. Boron can be added to alloys of the invention, in an amount up to about 0.05%, to improve hot strength and fabricability.
  • Vanadium is sometimes employed in certain corrosion resistant alloys which operate near room temperature. It has also been used in high speed tool steels as well as in a few nickel-base superalloys. In alloys in which vanadium was substituted for columbium, but which were otherwise in accordance with the invention, rupture life over the full temperature range was drastically reduced. Alloy HP-849 is an example of this effect.
  • a titanium content greater than about 0.45% in alloys otherwise of the invention causes erratic results; sometimes rupture life and ductility are not damaged by higher contents, but sometimes they drop considerably. This effect may be due to the tendency for large amounts of titanium to produce a dross and resultant defects during air melting.
  • Mischmetal or any combination of rare earth elements all appear to behave in the same manner in alloys of the invention. Ductility and rupture life drop considerably in alloys of the invention when the maximum of about 0.3% is exceeded.
  • the misch metal employed for the data reported herein had a cerium + lanthanum content of 73% and had a total rare earth content of 97.5%. In practice it has been found that to achieve a desired rare earth elements content in an alloy of the invention it may be necessary to add up to about 60% excess misch metal (based on Ce + La content) to achieve that content.
  • the following examples further illustrate the invention:
  • Heats of several different alloys were prepared in accordance with the invention by adding small quantities of molybdenum, tungsten, columbium, zirconium, titanium and mischmetal to otherwise basic ACI-type (HF, HH, HK, HN and HP) alloys.
  • Well-risered standard ASTM test bar keel blocks were cast from each heat. The composition of these alloys is set forth in Table III, with the balance in each instance being essentially iron.
  • Heat numbers beginning with HF, HH, HK, HN and HP refer to the ACI H-type base alloy employed.
  • Heats of several comparative alloys not of the invention were also prepared and cast into standard test bar keel blocks.
  • the composition of these alloys is set forth in Table IV, with the balance in each instance being essentially iron.
  • HK-827 also contains 2.99% Co
  • CHSX-9 contains 3.07% Co
  • 3 HP-849 contains 0.31%V.
  • 5 HP-853 also contains 0.026% Al 35 and 0.0031% B.
  • 6 HP-869 also contains 0.035%B.
  • 7 SUPERTHERM also contains 15.1% Co.
  • 8 N-155 also contains 20.2% Co.
  • 8 REE rare earth elements. Amount reported is 1.33 times the determined amount of CE + La.
  • the true unit stress will therefore be somewhat higher than the calculated starting unit stress before any deterioration takes place. Also, as a typical metallic test bar deforms over time under stress at high temperature it lengthens and necks down to a smaller cross sectional area. The actual or true stress throughout most of the test period is therefore higher than the calculated stress determined from the beginning test bar dimensions.
  • the ASTM Standard E 139 rupture test provides for several different diameters of test bars. For equal unit stress values in undamaged test bars it may be seen from simple geometrical considerations that for a given depth of surface penetration a smaller diameter bar will have a larger actual unit stress after a long period of time than will a larger diameter bar with the same depth of surface penetration.
  • test bar diameter employed by Heyer et al, (U.S. Pat. No. 4,077,801) in testing the Thermax alloys is not given but all other tests reported herein were conducted on ASTM E .39 1/4-inch diameter test bars and therefore represent comparative conditions. It may be seen that comparative alloy HP-838 conforms to alloys of the invention except for its high tungsten content. This alloy displays much shorter rupture life in all conditions than the alloys of the invention. Alloy HP-853 generally conforms to the alloy disclosed in Japan J60059-0JIA except as to zirconium content. Other comparative alloys similar to the invention, but not conforming in some way, all show variously shorter rupture lives than alloys of the invention.
  • Test data at 5000 psi and 1800°F for alloys 3010 and 3011 were taken as representative of alloys of U.S. Pat. No. 4,861,547 which are alloys of the HH type.
  • the HF-861 alloy of the invention showed superior rupture life in all of the tests compared to • 515 and did not oxidize nearly as severely as the latter at any temperature probably because of the rare earth component in its formulation. In a more practical range for this alloy, the '515 test bar ruptured at 519.3 hours at 1600° and 6000 psi stress. Alloy HF-861 of the invention had not ruptured at 3000 hours under the same conditions.
  • the HN-862 alloy of the invention also provided much improved rupture life over standard ACI-type HN alloys.
  • comparative alloy N-155 contains over 6% of four of the six critical elements of the invention ( , Cb, Mo, Ti, Zr and rare earth component) alloy HF-873, having the same base as N-155 and containing the critical elements in proportions within the ranges of the invention, has obviously far superior rupture life at various temperatures and loads.
  • the experimental alloy CHSX-10 compared well with both HH-type and HK-type alloys of the invention but at an enormously higher materials cost in view of containing 52% Ni, 37% Cr and 5% .
  • the ACI alloys typically suffer significant loss of ductility after aging for some period at elevated temperature. Some of the grades have only about 10% to 13% room temperature elongation even prior to such aging. Attempts to improve their hot strengths by substantial additions or increases of some elements, such as cobalt and tungsten, further reduce ductility.
  • Table XVII also lists such values from stress rupture tests of a number of grades of jet engine type super alloys as well as from commercial heats of the alloy of U.S. Pat. No. 3,127,265, known by the tradename Supertherm. Ranges of elongations of the similar alloys of Heyer, et al, U.S. Pat. No. 4,077,801, sold under the tradename of Thermax, were taken from data in that patent. All tests were conducted after the test bars were aged at 1450°F for 100 hours. TABLE XVII
  • the alloys of the invention elongated considerably before rupture. These elongation values often corresponded to reductions in cross sectional area at the time of rupture of 50% to 94%; that is, the final cross sectional area at the necked down portion of the test bar ranged from about half to a mere 6% of the original area. These results demonstrate the exceptional abilities of the alloys of the invention to deform in service without rupturing despite their outstanding values of hot strength. I have observed from experience with production heats of various types of heat resistant alloys that those of less than about 7% elongation, when tensile tested at room temperature, will present serious welding problems in many castings' configurations.

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Abstract

Cette invention se rapporte à des alliages thermo-résistants et résistants à la corrosion utilisés pour la fabrication de pièces de construction de fours industriels et d'installations analogues nécessitant la résistance à chaud, une longévité et la résistance à la corrosion par les gaz chauds, à la cémentation et à la fatique thermique, ainsi qu'à des préalliages servant à produire de tels alliages. Les alliages sont composés d'additons de moins d'un pourcent en poids de chacun des composants suivants: le tungstène, le zircone, le molybdène, le niobium, le titane et un ou plusieurs éléments des terres rares, à des alliages deuxième titre de types normalisés par la "Alloy Castings Institute Division of the Steel Founders Society of America" ou d'alliages deuxième titre similaires. Les préalliages sont composés de tous ces éléments à l'exception possible de Mo, combinés dans les proportions désirées, avec éventuellement une combinaison de fer, de nickel ou de chrome dont la teneur totale irait jusqu'à environ la moitié en poids des préalliages comme diluants partiels. Les préalliages qui en résultent sont toujours plus denses que les bains de fusion des alliages deuxième titre résistants à la chaleur.
EP19910911033 1990-04-16 1991-01-14 Heat resistant alloys Withdrawn EP0477363A4 (en)

Applications Claiming Priority (2)

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US509717 1983-06-30
US50971790A 1990-04-16 1990-04-16

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EP0477363A1 true EP0477363A1 (fr) 1992-04-01
EP0477363A4 EP0477363A4 (en) 1993-01-20

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EP19910911033 Withdrawn EP0477363A4 (en) 1990-04-16 1991-01-14 Heat resistant alloys

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EP (1) EP0477363A4 (fr)
BR (1) BR9105720A (fr)
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WO (1) WO1991016467A1 (fr)

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US5501835A (en) * 1994-02-16 1996-03-26 Hitachi Metals, Ltd. Heat-resistant, austenitic cast steel and exhaust equipment member made thereof
CN101300371B (zh) * 2005-10-31 2011-02-09 株式会社久保田 析出微细的Ti-Nb-Cr碳化物或Ti-Nb-Zr-Cr碳化物的耐热合金
KR20110063660A (ko) * 2008-09-25 2011-06-13 보르그워너 인코퍼레이티드 터보차저 및 그 지지 디스크
KR101982877B1 (ko) * 2016-09-09 2019-05-28 현대자동차주식회사 Ni 저감형 고내열 주강
CN115354239A (zh) * 2022-08-17 2022-11-18 常熟市港城不锈钢装饰有限责任公司 一种耐热合金钢材及其制备方法

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US3135602A (en) * 1957-02-11 1964-06-02 Babcock & Wilcox Co 45% iron base austenitic cr-ni alloy with 18-22% cr, 27-32% ni or (ni+co) plus strengthening additions
US2857266A (en) * 1958-02-26 1958-10-21 Duraloy Company High temperature resistant alloys
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BE790197Q (fr) * 1970-03-23 1973-02-15 Pompey Acieries Alliage refractaire a base de fer resistant aux temperatures elevees eta la recarburation
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JP2725689B2 (ja) * 1992-06-09 1998-03-11 住友重機械工業株式会社 蓄冷器式冷凍機

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BR9105720A (pt) 1992-09-08
WO1991016467A1 (fr) 1991-10-31
EP0477363A4 (en) 1993-01-20
CA2058997A1 (fr) 1991-10-17

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