US3700428A - Method of preparation of alloys of refractory metals - Google Patents

Method of preparation of alloys of refractory metals Download PDF

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Publication number
US3700428A
US3700428A US41520A US3700428DA US3700428A US 3700428 A US3700428 A US 3700428A US 41520 A US41520 A US 41520A US 3700428D A US3700428D A US 3700428DA US 3700428 A US3700428 A US 3700428A
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solid
alloy
alloys
refractory
refractory metals
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US41520A
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English (en)
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Etienne Bonnier
Colette Allibert
Jean Driole
Alain Wicker
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Bpifrance Financement SA
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Agence National de Valorisation de la Recherche ANVAR
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting

Definitions

  • the present invention relates to a method of preparation of alloys of refractory metals, in which a solid homogeneous solution of niobium and at least one of two refractory metals such as tungsten or molybdenum is prepared under an inert atmosphere in a liquid bath of a carrier metal (nickel or copper), the said solid solution is separated from the liquid phase and the whole is rapidly cooled so as to solidify the liquid phase thus separated from the solid phase.
  • the separation operation is carried out either by centrifuging or by electro-magnetic means and said latter means may also constitute the heating means.
  • the present invention relates to a method of preparation of alloys of refractory metals, such as for example niobium-tungsten and/ or molybdenum.
  • the alloys are prepared by direct co-fusion from constituents such as niobium and tungsten or molybdenum.
  • the melting temperatures of the elements being very high (2,468 C. for niobium, 3,380 C. for tungsten, 2,615 C. for molybdenum, for example) recourse is had in practice to the use of an electric arc furnace or an electronic bombardment furnace.
  • the operation is effected by progressive enrichment with added metal, which necessitates a number of melts, generally six to eight. This method is therefore long, uneconomic and very expensive. In both cases, the melts do not make it possible to obtain alloys having a homogeneous strusture.
  • Alloys of two refractory metals have also been prepared by the simultaneous deposit on a support of the vapours of these refractory metals. This method is however extremely costly and is in practice only applied for the production of thin layers.
  • the present invention has for its starting point the discovery that certain ternary systems such as Nb-W-Cu and Nb-Mo-Cu possess at high temperature, for example of the order of l,900 C., a field having two phases, constituted by a homogeneous solid solution of Nb-W or Nb-Mo respectively in equilibrium with a liquid Cu-Nb, which field furthermore covers almost completely the range of concentrations.
  • the method according to the invention is essentially characterized in that all the constituents of the alloy with a non-refractory carrier metal, chosen for its high solubility in the liquid state with one of the refractory metals and low solubility with the desired alloy, in that an inert atmosphere is created around these various constituents, and in that their temperature is increased at least up to the melting point of the said vector metal but below the melting points of the most meltable refractory metal and of the alloy formed by the carrier metal and the other refractory metals, in that the temperature is maintained for a period of time suflicient to reach an equilibrium between a solid phase constituted by a solid solution of the refractory metals and a liquid solution composed of an alloy of one or more refractory metals with the said carrier metal, in that the said solid phase is separated from the liquid phase, and in that a final cooling is effected so as to solidify the liquid phase thus separated from the solid phase.
  • This method permits the preparation of an extremely wide range of solid solutions with a base of niobiumtungsten and/or molybdenum.
  • the choice of the carrier metal is determined by various considerations:
  • reefractory metal It should preferably form with the reefractory metal a liquid alloy having a density different from that of the solid solution in equilibrium, in order that mechanical separation may be possible, or if it does not fulfil this condition, it must have differences of behviour with respect to the solid solution, under the action of an alternating electric field, which are sufiicient to carry out an electro-magnetic separation.
  • the choice of the preparation temperature is located at the same time well above the melting temperature of the carrier metal (copper 1,083 C., nickel 1,453 C.) and well below the melting temperature of niobium and of that of the alloy formed by the vector metal and the refractory metals. It is this reduction of the operating temperature on the one hand and the uniformity of the product obtained on the other which form the whole advantage of the method, permitting the preparation of this alloy under conditions which can be obtained in practice and on a large scale. Experience has shown that it is possible to work at temperatures lower than 2,000 C., and in particular that at 1,900 C., excellent results are obtained.
  • the duration of the treatment is governed by the rise in temperature and by obtaining thermo-dynamic equilibrium between the liquid and solid phases. As the temperature increases, this equilibrium is reached more rapidly, and it may be stated by way of example that the duration of the operation at a temperature of l,900 C. is of the order of one to two hours.
  • the separation of the liquid and solid phases may be carried out by following either of the two methods of operation below:
  • the solid phase is retained by the electro-magnetic forces, either on the walls of the crucible or, as the case may be, on a support which can be the sheath of the thermo-couple just above the liquid phase with which it remains in equilibrium through the intermediary of a liquid film.
  • the solid solution thus collected has the appearance of a mass of grains of homogeneous composition, all having the same concentration of niobium and tungsten or molybdenum, coated with a fine film of alloy produced by the liquid phase.
  • Micrographic examination of the product shows that the grains are constituted by a single homogeneous phase and not by a composite agglomerate of niobium with tungsten and/or molybdenum.
  • the main characteristics of this alloy depend on the respective quantities of niobium with respect to tungsten and/or molybdenum, but they show inter alia excellent refractory qualities.
  • FIG. 1 is a view in cross-section of a crucible for separating by centrifuging, the solid and liquid phases being shown at the end of the centrifuging operation;
  • FIG. 2 is a view in cross-section of a crucible for separating by electro-magnetic process, the liquid and solid phases being shown at the end of the separation operation.
  • EXAMPLE 1 There are available copper (Cu) serving as the carrier metal, niobium (Nb) and tungsten (W).
  • the vector metal can be utilized in very diverse forms; ingots, grains, etc., whereas it is advantageous for the refractory metals to be in the form of coarse powder, which permits the process of formation of the solid solution to be accelerated.
  • the choice of the crucible depends essentially on the working temperature: at 1,600 C., an alumina crucible may be quite adequate, between 1,-600 C. and 2,000 C., a zirconia crucible is chosen, and above 2,000 C., it is necessary to employ a crucible of beryllium oxide.
  • a mixture is made of 85 grams of Cu, 10 grams of Nb, and grams of W, which corresponds to the following proportions given in percentages of the total weight:
  • This mixture is introduced into a cylindrical crucible of the type shown in FIG. 1, comprising an outer body 2 of graphite and an internal lining 3 of zirconia.
  • a thermometer probe 4 is engaged in the crucible and heating is effected by electro-magnetic induction.
  • Means (not shown) are provided for maintaining a neutral atmosphere of argon in and around the crucible, these means further incorporating means for rapid putting into circulation of cold gas.
  • the method of operation is as follows:
  • the crucible is placed in a furnace which is previously exhausted to a vacuum of torr and then filled with inert gas (argon or helium) at atmospheric pressure. Heating is carried out by induction either at medium frequency of the order of 10 kc. or at high frequency of the order of 400 kc.
  • the rise in temperature programmed following a linear function of the power supply to the furnace, permits the desired temperature to be obtained in a fairly short time (for example 30 minutes to reach l,900 C.).
  • the mixture is heated to l,900 C. and is held at this tmeperature for 1 hour 30 minutes.
  • the crucible is set in rotation at 2,000 r.p.m. for 15 minutes, while maintaining the temperature at 1,900 C.
  • abrupt cooling is effected, either naturally by simply stopping the heating (rate of cooling of the order of 950 C./min.) or by tempering the alloy by a rapid circulation of argon or helium round the crucible.
  • the mass S having a weight of 8 grams is constituted solely by niobium and tungsten, the proportions being 28% Nb and 72% W. It has been verified that this originates from a solid solution of these two substances.
  • the annular mass L has the form of a metal structure comprising an alloy of 7% of niobium and 93% of copper.
  • the centrifuging time is limited to 5 minutes and there are obtained:
  • EXAMPLE 3 There was employed a crucible with electromagnetic separation (FIG. 2) utilizing an induction heating means at a medium frequency of the order of 10 kc.; there is again employed a crucible 11 with an outer body 12 of graphite and an inner lining 13 of zirconia, equipped with a thermometer probe 14. In this case the crucible is not rotatably mounted, but the inductors 15 cause the production in the mixture placed in the crucible, of electric currents which are utilized not only to ensure the heating to 1,900 C., but also for the electro-magnetic separation of the solid phase from the liquid phase.
  • EXAMPLE 5 The same procedure is followed as in Example 3, but with a crucible having no thermometer probe 14, the measurement of temperature being effected by optical pyrometry with electro-magnetic separation, with a mixture of 100 grams of 30% of Cu, 61% of Nb and 9% of M0, which is heated by induction with a medium frequency current for 2 hours at l,900 C.
  • Electra-magnetic separation of the phases resulted in:
  • alloys thus obtained are those which correspond, amongst others, to their refractory capacity and, if so desired, to their use as super-conductors.
  • the alloys thus obtained are reduced to powder by grinding and utilized for the manufacture of any object following the usual techniques of powder metallurgy.
  • alloys with a base of niobium can be employed for the manufacture of parts of aeronautical devices. It should be noted that the residual presence or traces of the alloy coming from the liquid phase does not offer any disadvantage. On the contrary, in the technique of powder metallurgy, in particular of refractory metals, use is made of these elements approximately in the same quantities, so that their addition in the method according to the invention becomes useless.
  • a method of preparing an alloy consisting essentially of refractory metals which method comprises the steps of:
  • non-refractory metal being highly soluble in one of said refractory metals when in a liquid state, but only slightly soluble in the alloy to be prepared;
  • refractory metals used are selected from the group consisting of niobium, tungsten and molybdenum and said temperature is maintained for from one to two hours.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US41520A 1969-05-30 1970-05-28 Method of preparation of alloys of refractory metals Expired - Lifetime US3700428A (en)

Applications Claiming Priority (1)

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FR6916424A FR2044921A5 (nl) 1969-05-30 1969-05-30

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US (1) US3700428A (nl)
AT (1) AT300384B (nl)
DE (1) DE2026445C3 (nl)
FR (1) FR2044921A5 (nl)
NL (1) NL167473C (nl)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0429019A1 (en) * 1989-11-20 1991-05-29 Nkk Corporation Method for producing a high reactive alloy

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0429019A1 (en) * 1989-11-20 1991-05-29 Nkk Corporation Method for producing a high reactive alloy

Also Published As

Publication number Publication date
NL167473B (nl) 1981-07-16
FR2044921A5 (nl) 1971-02-26
DE2026445A1 (de) 1970-12-10
DE2026445B2 (de) 1973-05-30
NL7007800A (nl) 1970-12-02
AT300384B (de) 1972-07-25
DE2026445C3 (de) 1973-12-13
NL167473C (nl) 1981-12-16

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