EP0514480B1 - Alliage de haute resistance et de haute tenacite a la rupture - Google Patents

Alliage de haute resistance et de haute tenacite a la rupture Download PDF

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Publication number
EP0514480B1
EP0514480B1 EP91904760A EP91904760A EP0514480B1 EP 0514480 B1 EP0514480 B1 EP 0514480B1 EP 91904760 A EP91904760 A EP 91904760A EP 91904760 A EP91904760 A EP 91904760A EP 0514480 B1 EP0514480 B1 EP 0514480B1
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EP
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Prior art keywords
max
alloy
fracture toughness
set forth
age
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EP91904760A
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German (de)
English (en)
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EP0514480A4 (en
EP0514480A1 (fr
Inventor
Raymond M. Hemphill
David E. Wert
Paul M. Novotny
Michael L. Schmidt
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CRS Holdings LLC
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CRS Holdings LLC
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Priority claimed from US07/475,773 external-priority patent/US5087415A/en
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    • 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
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt

Definitions

  • This invention relates to an age-hardenable, martensitic steel alloy, and in particular to such an alloy and an article made therefrom in which the elements are closely controlled to provide a unique combination of high tensile strength, high fracture toughness and good resistance to stress corrosion cracking in a marine environment.
  • an alloy designated as 300M has been used in structural components requiring high strength and light weight.
  • the 300M alloy has the following composition in weight percent: wt. % C 0.40-0.46 Mn 0.65-0.90 Si 1.45-1.80 Cr 0.70-0.95 Ni 1.65-2.00 Mo 0.30-0.45 V 0.05 min. and the balance is essentially iron.
  • the 300M alloy is capable of providing tensile strength in the range of 1930-2068mMPa (280-300ksi).
  • Higher fracture toughness is desirable for better reliability in components and because it permits non-destructive inspection of a structural component for flaws that can result in catastrophic failure.
  • An alloy designated as AF1410 is known to provide good fracture toughness as represented by K IC ⁇ 1100MPa m (100ksi in ).
  • the AF1410 alloy is described in U.S. Patent No. 4,076,525 ('525) issued to Little et al. on February 28, 1978.
  • the AF1410 alloy leaves much to be desired with regard to tensile strength.
  • That application does not refer to the presence of calcium, magnesium or yttrium in the alloys.
  • a further object of this invention is to provide an alloy which, in addition to high strength and high fracture toughness, is designed to provide a high resistance to stress corrosion cracking in marine environments.
  • Another object of this invention is to provide a high strength alloy having a low ductile-to-brittle transition temperature.
  • Table 1 summarizes compositions of age-hardenable martensitic steel alloys as claimed in claim 1, in weight percent: Broad Intermediate Preferred C 0.2-0.33 0.20-0.31 0.21-0.27 Mn 0.05 max. 0.05 max. 0.05 max. Si 0.1 max. 0.1 max. 0.1 max. P 0.008 max. 0.008 max. 0.008 max. S 0.002 max. 0.002 max. 0.0020 max. Cr 2-4 2.25-3.5 2.5-3.3 Ni 10.5-15 10.75-13.5 11.0-12.0 Mo 0.75-1.75 0.75-1.5 1.0-1.3 Co 8-17 10-15 11-14 Ti 0.02 max. 0.02 max. 0.02 max. Al 0.01 max. 0.01 max.
  • the alloy according to the present invention as given in the claims is critically balanced to provide a unique combination of high tensile strength, high fracture toughness, and stress corrosion cracking resistance.
  • the ratio Ce/S is at least 2 to not more than 10 in the first aspect of the invention (claim 1).
  • the amount of carbon and/or cobalt are preferably adjusted downwardly so as to be within the lower half of their respective elemental ranges.
  • Carbon and cobalt are preferably balanced in accordance with the following relationships:
  • the alloy according to the present invention as given in the claims contains at least 0.2%, better yet, at least 0.20%, and preferably at least 0.21% carbon because it contributes to the good hardness capability and high tensile strength of the alloy primarily by combining with other elements such as chromium and molybdenum to form carbides during heat treatment. Too much carbon adversely affects the fracture toughness of this alloy. Accordingly, carbon is limited to not more than 0.33%, better yet, to not more than 0.31%, and preferably to not more than 0.27%.
  • Cobalt contributes to the hardness and strength of this alloy and benefits the ratio of yield strength to tensile strength (Y.S./U.T.S.). Therefore, at least 8%, better yet at least 10%, and preferably at least 11% cobalt is present in this alloy. for best results at least 12% cobalt is present. Above 17% cobalt the fracture toughness and the ductile-to-brittle transition temperature of the alloy are adversely affected. Preferably, not more than 15%, and better yet not more than 14% cobalt is present in this alloy.
  • Cobalt and carbon are critically balanced in this alloy to provide the unique combination of high strength and high fracture toughness that is characteristic of the alloy.
  • carbon and cobalt are preferably balanced in accordance with the following relationship:
  • Chromium contributes to the good hardenability and hardness capability of this alloy and benefits the desired low ductile-brittle transition temperature of the alloy. Therefore, at least 2%, better yet at least 2.25%, and preferably at least 2.5% chromium is present. Above 4% chromium the alloy is susceptible to rapid overaging such that the unique combination of high tensile strength and high fracture toughness is not attainable with the preferred age-hardening heat treatment. Preferably, chromium is limited to not more than 3.5%, and better yet to not more than 3.3%. When the alloy contains more than 3% chromium, the amount of carbon present in the alloy is preferably adjusted upwardly in order to ensure that the alloy provides the desired high tensile strength.
  • At least 0.75% and preferably at least 1.0% molybdenum is present in this alloy because it benefits the desired low ductile-brittle transition temperature of the alloy. Above 1.75% molybdenum the fracture toughness of the alloy is adversely affected. Preferably, molybdenum is limited to not more than 1.5%, and better yet to not more than 1.3%.
  • the % carbon and/or % cobalt is preferably adjusted downwardly in order to ensure that the alloy provides the desired high fracture toughness. Accordingly, when the alloy contains more than 1.3% molybdenum, the % carbon is preferably not more than the median % carbon for a given % cobalt as defined by equations a) and b) or a) and c).
  • Nickel contributes to the hardenability of this alloy such that the alloy can be hardened with or without rapid quenching techniques. Nickel benefits the fracture toughness and stress corrosion cracking resistance provided by this alloy and contributes to the desired low ductile-to-brittle transition temperature. Accordingly, at least 10.5%, better yet, at least 10.75%, and preferably at least 11.0% nickel is present. Above 15% nickel the fracture toughness and impact toughness of the alloy can be adversely affected because the solubility of carbon in the alloy is reduced which may result in carbide precipitation in the grain boundaries when the alloy is cooled at a slow rate, such as when air cooled following forging. Preferably, nickel is limited to not more than 13.5%, and better yet to not more than 12.0%.
  • manganese is present because manganese adversely affects the fracture toughness of the alloy.
  • up to 0.1% silicon, up to 0.01% aluminum, and up to 0.02% titanium can be present as residuals from small additions for deoxidizing the alloy.
  • the alloy can contain up to 0.030% cerium and up to 0.01% lanthanum.
  • the preferred method of providing cerium and lanthanum in this alloy is through the addition of mischmetal during the melting process in an amount sufficient to recover effective amounts of cerium and lanthanum in the alloy.
  • Effective amounts of cerium and lanthanum are present in this aspect when the ratio Ce/S is at least 2. When the Ce/S ratio is more than 15, the hot workability and tensile ductility of the alloy are adversely affected.
  • the ratio Ce/S is not more than 10 in this aspect.
  • the alloy contains not more than 0.01% cerium and not more than 0.005% lanthanum.
  • a small but effective amount of calcium can be present in this alloy in substitution for some or all of the cerium and lanthanum to benefit the fracture toughness provided by the alloy.
  • the amount of calcium in the alloy is in the range from 0.002% up to the combined maximum amounts of cerium and lanthanum in the Table I above, such that the total amount of cerium, lanthanum and calcium is not greater than the combined maximum amounts of cerium and lanthanum in the Table I above. Excellent results have been obtained when the alloy contains 0.002% calcium.
  • Other rare earth metals, magnesium or yttrium can also be present in this alloy in place of some or all of the cerium, lanthanum or calcium in yet another aspect of the invention (claim 11) to provide the beneficial sulfide shape control.
  • the balance of the alloy according to the present invention is iron except for the usual impurities found in commercial grades of alloys intended for similar service or use.
  • the levels of such elements must be controlled so as not to adversely affect the desired properties of this alloy.
  • phosphorus is limited to not more than 0.008%.
  • Sulfur adversely affects the fracture toughness provided by this alloy. Accordingly, sulfur is restricted to 0.002% max. Best results are obtained when the alloy contains not more than 0.001% sulfur.
  • Tramp elements such as lead, tin, arsenic and antimony are limited to 0.003% max. each, better yet to 0.002% max. each, and preferably to 0.001% max each.
  • Oxygen is limited to not more than 20 parts per million (ppm) and nitrogen to not more than 40 ppm.
  • the alloy of the present invention is readily melted using conventional vacuum melting techniques. For best results, as when additional refining is desired, a multiple melting practice is preferred. The preferred practice is to melt a heat in a vacuum induction furnace (VIM) and cast the heat in the form of an electrode. The alloying addition for sulfide shape control referred to above is preferably made before the molten VIM heat is cast. The electrode is then remelted in a vacuum arc furnace (VAR) and recast into one or more ingots. Prior to VAR the electrode ingots are preferably stress relieved at about 677°C (1250F) for 4-16 hours and air cooled. After VAR the ingot is preferably homogenized at about 1177-1232°C (2150-2250F) for 6- 24 hours.
  • VAR vacuum arc furnace
  • the alloy can be hot worked from about 1232°C (2250F) to about 816°C (1500F).
  • the preferred hot working practice is to forge an ingot from about 1177-1232°C (2150-2250F) to obtain at least a 30% reduction in cross sectional area.
  • the ingot is then reheated to about 982°C (1800F) and further forged to obtain at least another 30% reduction in cross sectional area.
  • the alloy according to the present invention is austenitized and age hardened as follows. Austenitizing of the alloy is carried out by heating the alloy at about 843-599°C (1550-1650F) for about 1 hour plus about 2 minutes per cm (5 minutes per inch) of thickness and then quenching in oil. The hardenability of this alloy is good enough to permit air cooling or vacuum heat treatment with inert gas quenching, both of which have a slower cooling rate than oil quenching. Whatever quenching technique is used, the quench rate is preferably rapid enough to cool the alloy from the austenitizing temperature to about 65°C (150F) in about 2h.
  • this alloy is preferably austenitized at about 843-871°C (1550-1600F), whereas when the alloy is to be vacuum treated or air hardened it is preferably austenitized at about 857-899°C (1575-1650F). After austenitizing, the alloy is preferably cold treated as by deep chilling at about -73°C (-100F) for 1/2 to 1 hour and then warmed in air.
  • Age hardening of this alloy is preferably conducted by heating the alloy at about 454-496°C (850-925F) for about 5 hours followed by cooling in air.
  • the alloy according to the present invention provides an ultimate tensile strength of at least about 1930MPa (280ksi) and longitudinal fracture toughness of at least about 110MPa m (100ksi in ).
  • the alloy can be aged within the foregoing process parameters to provide a Rockwell hardness of at least 54 HRC when it is desired for use in ballistically, tolerant articles.
  • VIM heats Five 180kg (400lb) VIM heats were prepared and each was split cast into 90kg (200lb) VAR electrode-ingots. Prior to casting each of the electrode ingots a predetermined addition of mischmetal or calcium was added to the respective VIM heats. The amount of each addition was selected to result in a desired retained-amount after refining.
  • the electrode-ingots were cooled in air, stress relieved at 677°C (1250F) for 16h and then air cooled. The electrode-ingots were then refined by VAR and vermiculite cooled. The VAR ingots were stress relieved at 677°C (1250F) for 16h and cooled in air.
  • compositions of the VAR ingots are set forth in weight percent in Table II below.
  • Heats 1 and 2 are examples of the present invention (claim 1)
  • Heats 4 - 7 are examples of the present invention (claim 9)
  • Heats 3 and A-C are comparative alloys. Heat No.
  • the VAR ingots Prior to forging, the VAR ingots were homogenized at 1232°C (2250F) for 6h. The ingots were then press forged from the temperature of 1232°C (2250F) to 7.6 cm high by 12.7 cm. (3 in high by 5in wide) bars. The bars were reheated to 982°C (1800F), press forged to 3.8 x 10.2 cm (1-1/2in x 4in) bars, and then cooled in air. The forged bars were annealed at 677°C (1250F) for 16h and then air cooled.
  • Standard longitudinal tensile specimens (0.64cm-0.252 inch-gage diameter by 2.5cm-1 in-gage length) were machined from the annealed bars.
  • the tensile specimens were austenitized in salt for 1h at 885°C (1625F), vermiculite cooled, deep chilled at -73°C (-100F) for lh, and then warmed in air.
  • the specimens were then age hardened for 5h at 482°C (900F) and air cooled.
  • Standard compact tension fracture toughness specimens were machined with a longitudinal orientation from the remains of the annealed bars.
  • the fracture toughness specimens were austenitized, 20 deep chilled, and age hardened in the same manner as the tensile specimens except for being air cooled from the austenitizing temperature.
  • the results of room temperature tensile tests on the duplicate specimens are shown in Table III 25 including the 0.2% offset yield strength (0.2% Y.S.) and the ultimate tensile strength (U.T.S.) in MPa and ksi, as well as the percent elongation (% El.) and percent reduction in area (% R.A.)
  • the results of room temperature fracture toughness testing in 30 accordance with ASTM Standard Test E399 are also shown in Table III as K IC in MPa m and ksi in . Heats B and C were not tested because they could not be press forged.
  • the data of Table III show that the alloy according to the present invention provides an ultimate tensile strength of at least 1930MPa (280ksi) in combination with high fracture toughness as represented by a K IC of at least 110MPa m (100ksi in ).
  • the alloy according to the present invention is useful in a variety of applications requiring high strength and low weight, for example, aircraft landing gear components; aircraft structural members, such as braces, beams, struts, etc.; helicopter rotor shafts and masts; and other aircraft structural components which are subject to high stress in service.
  • the alloy of the present invention could be suitable for use in jet engine shafts.
  • This alloy can also be aged to very high hardness which makes it suitable for use as lightweight armor and in structural components which must be ballistically tolerant.
  • the present alloy is, of course, suitable for use in a variety of product forms including billets, bars, tubes, plate and sheet.
  • the alloy according to the present invention provides a unique combination of tensile strength and fracture toughness not provided by known alloys.
  • This alloy is well suited to applications where high strength and low weight are required.
  • the present alloy has a low ductile-to-brittle transition temperature which renders it highly useful in applications where the in-service temperatures are well below zero degrees Fahrenheit. Because this alloy can be vacuum heat treated, it is particularly advantageous for use in the manufacture of complex, close tolerance components. Vacuum heat treatment of such articles is desirable because the articles do not undergo any distortion as usually results from oil quenching of such articles made from known alloys.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
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Claims (13)

  1. Alliage d'acier martensitique, durcissable par vieillissement, qui fournit une résistance élevée et une ténacité élevée, ledit alliage comprenant, en pour cent en poids, Carbone 0,2-0,33 Manganèse 0,05 au maximum Silicium 0,1 au maximum Phosphore 0,008 au maximum Soufre 0,002 au maximum Chrome 2-4 Nickel 10,5-15 Molybdène 0,75-1,75 Cobalt 8-17 Titane 0,02 au maximum Aluminium 0,01 au maximum Plomb 0,003 au maximum Etain 0,003 au maximum Arsenic 0,003 au maximum Antimoine 0,003 au maximum Oxygène 20 ppm au maximum Azote 40 ppm au maximum,
    dans lequel, de manière à se combiner avec le soufre disponible pour le contrôle de forme des sulfures de sorte que ledit alliage fournisse une ténacité longitudinale à température ambiante KIc d'au moins 110 MPa m (100 ksi in ) pour une résistance à la traction à température ambiante d'au moins 1930 MPa (280 ksi) quand ledit alliage est à l'état durci par vieillissement, l'alliage contient en plus du cérium dans une quantité allant jusqu'à 0,030% en poids et du lanthane dans une quantité allant jusqu'à 0,01% en poids, le rapport Ce/S étant de 2 à 10, et le restant dudit alliage étant du fer, à l'exception des impuretés habituelles.
  2. Alliage selon la revendication 1, contenant au moins 0,20% de carbone.
  3. Alliage selon la revendication 1, contenant au moins 10,75% de nickel
  4. Alliage d'acier martensitique, durcissable par vieillissement, selon la revendication 1, contenant % en poids Carbone 0,20 - 0,31 Manganèse 0,05 au maximum Soufre 0,002 au maximum Chrome 2,25 - 3,5 Nickel 10,75 - 13,5 Molybdène 0,75 - 1,5 Cobalt 10 - 15.
  5. Alliage selon l'une quelconque des revendications 1 à 4, caractérisé en ce que a) %Co est ≤35 - 81,8 (%C)
  6. Alliage selon l'une quelconque des revendications 1 à 5, caractérisé en ce que b) %Co est ≥ 25,5 - 70 (%C)
  7. Alliage selon l'une quelconque des revendications 1 à 6, caractérisé en ce que c) %Co est ≥ 26,9 - 70 (%C)
  8. Alliage selon la revendication 6 ou 7, caractérisé en ce que, quand %Mo > 1,3, %C n'est pas de plus que la moyenne %C pour un %Co donné, tel qu'il est défini par les relations a) et c).
  9. Alliage d'acier martensitique, durcissable par vieillissement, qui fournit une résistance élevée et une ténacité élevée, ledit alliage comprenant, en pour cent en poids, Carbone 0,2-0,33 Manganèse 0,05 au maximum Silicium 0,1 au maximum Phosphore 0,008 au maximum Soufre 0,002 au maximum Chrome 2-4 Nickel 10,5-15 Molybdène 0,75-1,75 Cobalt 8-17 Titane 0,02 au maximum Aluminium 0,01 au maximum Plomb 0,003 au maximum Etain 0,003 au maximum Arsenic 0,003 au maximum Antimoine 0,003 au maximum Oxygène 20 ppm au maximum Azote 40 ppm au maximum,
    dans lequel, de manière à se combiner avec le soufre disponible pour le contrôle de forme des sulfures de sorte que ledit alliage fournisse une ténacité longitudinale à température ambiante KIC d'au moins 110 MPa m (100 ksi in ) pour une résistance à la traction à température ambiante d'au moins 1930 MPa (280 ksi) quand ledit alliage est à l'état durci par vieillissement, l'alliage contient en plus jusqu'à une quantité maximale de 0,030% en poids de cérium, jusqu'à une quantité maximale de 0,01% en poids de lanthane, et une quantité effective de calcium dans le domaine de 0,002 % en poids jusqu'aux quantités maximales combinées de cérium et de lanthane, de telle sorte que la quantité totale de cérium, de lanthane et de calcium ne soit pas supérieure aux quantités combinées maximales de cérium et de lanthane, et le restant dudit alliage étant du fer, à l'exception des impuretés habituelles.
  10. Alliage selon la revendication 9, contenant pas plus de 0,001% en poids de soufre.
  11. Alliage selon l'une quelconque des revendications 1 à 10, qui est modifié par la substitution de magnésium, d'yttrium ou d'un métal de terres rares autre que le cérium ou le lanthane pour au moins une portion du cérium et du lanthane ou du calcium, l'élément additionnel étant utilisé dans une quantité suffisante pour se combiner au soufre disponible pour le contrôle de forme des sulfures, de sorte que l'alliage fournisse une ténacité longitudinale à température ambiante KIc d'au moins 110 MPa√m (100 ksi √in) pour une résistance à la traction à température ambiante d'au moins 1930 MPa (280 ksi), quand ledit alliage est à l'état durci par vieillissement.
  12. Alliage d'acier martensitique, durcissable par vieillissement, selon la revendication 1, contenant % en poids Carbone 0,21 - 0,27 Manganèse 0,05 au maximum Soufre 0,0020 au maximum Chrome 2,5 - 3,3 Nickel 11,0 - 12,0 Molybdène 1,0 - 1,3 Cobalt 11 - 14 Cérium 0,01 au maximum,
    et caractérisé en ce que le rapport Ce/S est de 2 - 10.
  13. Article durci par vieillissement formé d'un alliage d'acier martensitique selon l'une quelconque des revendications 1 à 12, ledit article ayant une résistance à la traction longitudinale à température ambiante d'au moins 1930 MPa (280 ksi) et une ténacité longitudinale à température ambiante KIc d'au moins 110 MPa m (100 ksi in ) .
EP91904760A 1990-02-06 1991-02-05 Alliage de haute resistance et de haute tenacite a la rupture Expired - Lifetime EP0514480B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US07/475,773 US5087415A (en) 1989-03-27 1990-02-06 High strength, high fracture toughness structural alloy
US475773 1990-02-06
PCT/US1991/000779 WO1991012352A1 (fr) 1990-02-06 1991-02-05 Alliage de haute resistance et de haute tenacite a la rupture

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EP0514480A1 EP0514480A1 (fr) 1992-11-25
EP0514480A4 EP0514480A4 (en) 1993-01-27
EP0514480B1 true EP0514480B1 (fr) 2001-04-04

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JP (2) JP2683599B2 (fr)
AT (1) ATE200309T1 (fr)
CA (1) CA2073460C (fr)
DE (1) DE69132572T2 (fr)
ES (1) ES2156854T3 (fr)
IL (1) IL97154A (fr)
WO (1) WO1991012352A1 (fr)

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Publication number Priority date Publication date Assignee Title
US5866066A (en) * 1996-09-09 1999-02-02 Crs Holdings, Inc. Age hardenable alloy with a unique combination of very high strength and good toughness
CA2691795A1 (fr) * 2007-06-26 2008-12-31 Crs Holdings, Inc. Materiau d'arbre rotatif a tenacite elevee, a resistance elevee
JP6427499B2 (ja) 2012-12-19 2018-11-21 ヒルズ・ペット・ニュートリシャン・インコーポレーテッド 動物用食品組成物および製造方法
US10337079B2 (en) 2015-05-22 2019-07-02 Daido Steel Co., Ltd. Maraging steel
US20210198762A1 (en) 2019-04-26 2021-07-01 Crs Holdings, Inc. Ultra-high strength alloy

Citations (1)

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EP0390468A1 (fr) * 1989-03-27 1990-10-03 Crs Holdings, Inc. Alliage de construction à haute résistance mécanique et à tenacité élevée

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Publication number Priority date Publication date Assignee Title
EP0390468A1 (fr) * 1989-03-27 1990-10-03 Crs Holdings, Inc. Alliage de construction à haute résistance mécanique et à tenacité élevée

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Publication number Publication date
ATE200309T1 (de) 2001-04-15
EP0514480A4 (en) 1993-01-27
IL97154A (en) 1996-01-31
DE69132572D1 (de) 2001-05-10
IL97154A0 (en) 1992-05-25
CA2073460A1 (fr) 1991-08-07
EP0514480A1 (fr) 1992-11-25
JP2683599B2 (ja) 1997-12-03
JPH03243747A (ja) 1991-10-30
WO1991012352A1 (fr) 1991-08-22
JPH05502477A (ja) 1993-04-28
DE69132572T2 (de) 2001-09-27
CA2073460C (fr) 1999-12-14
ES2156854T3 (es) 2001-08-01
JPH0689436B2 (ja) 1994-11-09

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