US3802851A - Tungsten alloy products - Google Patents

Tungsten alloy products Download PDF

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Publication number
US3802851A
US3802851A US00248933A US24893372A US3802851A US 3802851 A US3802851 A US 3802851A US 00248933 A US00248933 A US 00248933A US 24893372 A US24893372 A US 24893372A US 3802851 A US3802851 A US 3802851A
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United States
Prior art keywords
product
thoria
tungsten
concentration
growth
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Expired - Lifetime
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US00248933A
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English (en)
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T Dunham
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General Electric Co
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General Electric Co
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Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US00248933A priority Critical patent/US3802851A/en
Priority to GB1313973A priority patent/GB1407902A/en
Priority to FR7310058A priority patent/FR2182883B1/fr
Priority to JP3195373A priority patent/JPS538288B2/ja
Priority to DE19732314274 priority patent/DE2314274C3/de
Priority to HUGE938A priority patent/HU166091B/hu
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Publication of US3802851A publication Critical patent/US3802851A/en
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0031—Matrix based on refractory metals, W, Mo, Nb, Hf, Ta, Zr, Ti, V or alloys thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12014—All metal or with adjacent metals having metal particles
    • Y10T428/12021—All metal or with adjacent metals having metal particles having composition or density gradient or differential porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12014—All metal or with adjacent metals having metal particles
    • Y10T428/12153—Interconnected void structure [e.g., permeable, etc.]

Definitions

  • the conventional thoriated tungsten materials having a uniform distribution of thoria particles throughout the tungsten matrix are effective in increasing the recrystallization temperature of tungsten and, in addition, offer some restraint to grain boundary motion at lamp-operating temperatures thereby stabilizing a small grain size.
  • the resulting small tungsten grain structure is not creep resistant andis subject to lamp filament sag and other maladies common to small grain size materials.
  • a dispersion alloy product of tungsten containing the graingrowth-promoting additives and thoria with the maximum concentration of thoria being located at the exterior surface of said dispersion alloy product and with said thoria concentration continuously diminishing with increasing distance to the interior portion of the dispersion alloy product provides all of the foregoing desired advantages.
  • a liquid diffusion process is employed to impregnate a porous compact of tungsten particles containing a uniform distribution of the grain-growth-promoting additives.
  • the tungsten powder compact was prepared by treating blue tungsten oxide powder (approximately W0 with aqueous solutions of potassium silicate and aluminum chloride and then reducing the chemically treated oxide to metallic tungsten by heating in hydrogen.
  • the pressed compact of tungsten particles containing the grain-growth-promoting additives and having an interconnected pore structure was first presintered at l,200C in hydrogen and then soaked in water until all pores were essentially filled.
  • the water-filled compact was then immersed in a water solution of thorium nitrate for various time periods depending uponthe thickness of the thoriated tungsten alloy shell desired in the final alloy product. Removal of the solvent was accomplished by drying the impregnated compact which was then processed by conventional presintering and sintering operations.
  • the end result is a sintered material having a continuously diminishing concentration gradient of thoria in the direction of the central core of the porous compact.
  • the maximum thoria concentration is produced at the exterior-most surface portion of the porous compact with said concentration continuously diminishing as the distance increases to the center core of the porous compact in accordance with operating principles of liquid diffusion.
  • the thoria concentration uniformly decreases from the surface to a very small value near the central axis so that a portion of the interior of the ingot contains essentially no ThO Mechanically working the sintered product at high temperatures, such as by forging, swaging and wire drawing, converts the crystalline structure into a fibrous elongated grain structure.
  • the graingrowth-promoting additives produce exaggerated grain growth in the central core compared with tungsten crystals not containing such additives.
  • the presence of increasing amounts of thoria particles in the surface portion of the dispersion alloy product is effective in restraining grain growth of the tungsten crystals and providing smaller size tungsten crystals at this location when certain thermal treatments are given the material.
  • Such a tungsten grain structure at the core of the wire is effective in minimizing sag which is primarily a creep process as well as the further problem of offsetting which is due to slip in grain boundaries forming large angles with the longitudinal working direction.
  • the composite crystalline structure of the tungsten matrix in the final product should also be obtainable although possibly to a lesser degree in a dispersion alloy product containing other types of additives.
  • the diffusion time By using different combinations of the presintered ingot porosity, the diffusion time, the solution concentration of the thorium compound, and the concentration of the grain-growth-promoting additives in the original compact, it becomes thereby possible to vary the tungsten crystal size upon recrystallization in the final product from a relatively large grain size internal core with a surrounding shell of small grain size to a more uniform large grain size throughout the cross section.
  • the recrystallized tungsten grain size and distribution are also dependent upon the heat treatment schedule employed to obtain the final product.
  • FIG. I is a graph depicting concentration gradients of ThO in three different 14 mil wires prepared in accordance with the present invention. These data were obtained using a point-by-point analysis by the electron beam microprobe technique. These curves are most useful in illustrating the existence of gradients as well as the difference between the concentration gradients in three different preparations.
  • FIG. 2 is a photomicrograph ofa longitudinal section of one type of l4 mil wire obtained by practice of the present invention. Magnification is at 100 times.
  • FIG. 3 illustrates the effect of heating rate on the recrystallized structure of another type of 14 mil wire product obtained by practice of the present invention. Magnification is at 100 times.
  • the liquid diffusion process practiced in the present invention comprises soaking a porous compact of tungsten having uniformly dispersed therein graingrowth-promoting additives disclosed in US. Pat No. 1,410,499 with an inert liquid solvent of a soluble thorium compound until the pore structure of said compact is essentially filled with the solvent and thereafter immersing the solvent-filled compact in a liquid solution of the thorium compound for a sufficient time period to permit liquid diffusion of the dissolved thorium compound into at least a portion of the solvent contained in the pores of the compact.
  • inert liquid solvent a solvent for the thorium compound which can be removed by drying or heating the liquid-filled compact without leaving a residue in the pore structure or undergoing any significant chemical reaction with the tungsten material.
  • a second soluble additive in the same liquid solvent for the thorium compound or a different solvent can be used to fill the pore structure than is employed to dissolve one or more additives.
  • EXAMPLE A A pressed compact measuring 17 mm X 22 mm in cross section was prepared having a tungsten composition which contained small residual amounts of Al, K and Si in accordance with the teachings of the aforementioned U.S. Pat. No. 1,410,499.
  • the presintered ingot weighing approximately 1.7 kg was soaked in distilled water until the interconnected pore structure of the compact was saturated and the liquid-filled ingot thereafter immersed in an aqueous Th(NO solution having a concentration of 260 grams ThO per liter of solution.
  • the liquid diffusion process was interrupted after approximately 4 hours by removing the compact from the thorium nitrate solution.
  • the compact was next dried slowly in a vacuum oven at approximately 400F, which removed all solvent from the pores of the compact while retaining a concentration gradient of the thorium additive as specified in Table I below.
  • the thorium additive-containing compact was next subjected to a conventional presintering operation at approximately l,200C in hydrogen which converted the thorium nitrate in the pores to thorium oxide (thoria) and thereafter sintered at approximately 2,400C in hydrogen for approximately 2 hours to produce a densified thoriated tungsten composition in accordance with the present invention having a density of approximately percent of the theoretical value.
  • Test specimens were obtained from sintered products produced in accordance with this example as well as in following Examples B and C in order to measure the thoria concentration gradient and observe the crystalline structures.
  • the test specimens were examined by a known autoradiograph technique and all found to have a visible concentration gradient of the thoria additive with maximum concentration being located at the exterior-most surface portion of the sintered compact. All thoria concentrations continuously diminished with increasing distance to the center portion of the compact along radii extending from its surface to the axis. Further comparisons of W-ThO materials made via the liquid diffusion process with conventionally made W-ThO materials were made.
  • thoria particles in the thoriated tungsten dispersion alloy products produced in accordance with the present invention were found to be uniformly smaller in size range without any significant agglomeration of thoria particles that was found when the products were produced from practice of conventional powder metallurgy techniques.
  • Table I summarizes some data pertaining to ingots prepared in accordance with Examples A, B and C of the present invention. These data were obtained using standard X-ray fluorescence techniques. Corner and axis values were obtained from small -inch cube sampics taken at these locations. The bulk value was obtained from a A-inch cross-sectional slice.
  • Example A The sintered compact of Example A was rolled, swaged and drawn to 14.6 mil wire in accordance with conventional tungsten working practice.
  • the approximate thoria concentration gradient in the prepared wire is reported in the accompanying FIG. 1 graph for all compositions of Examples A-C as determined by conventional microprobe measurement. Again, it can be noted from FIG. 1 that in each instance from the surface to the longitudinal axis of the wire there is at least a 10 percent less thoria concentration at the central axis than at the wire surface.
  • the Example A wire was also subjected to recrystallization by passing an electric current through the wire in a hydrogen atmosphere. More particularly, the wire was subjected for a 6-minute time period to approximately 70 percent of the fusion amperage which produced a large tungsten grain structure exhibiting sag or high temperature creep resistance far superior to either pure tungsten or conventional thoriated tungsten wire of the same size.
  • Observation of the photomicrograph illustrates a fine grain tungsten structure at the surface portion of the wire with a large grain structure of tungsten in the central core region.
  • this structure should exhibit improved performance as an incandescent filament in an electric lamp.
  • the small surface grain structure allows the filament in a lamp to absorb shock and vibration at high temperatures, while the larger grain interior structure provides resistance to filament sag.
  • EXAMPLE B A presintered compact having the same initial tungsten composition disclosed in Example A and containing the same solvent was impregnated by liquid diffusion with the same aqueous thorium nitrate solution for a time period of approximately 30 hours. The thoriumcontaining compact was also given the same heat treatment disclosed in Example A. A comparison of the values reported in Table I above for the dispersion alloy products obtained upon sintering the Examples A and B finds the longer diffusion time to effectively increase the thoria concentration both at the surface and central axis of the compact. The sintered compact was next processed to 14.6 mil wire as described in Example A,
  • Example B wire (FIG. 3a) exhibiting excellent sag resistance comparable to the control wire containing no thoria for both the 70 and 80 percent current settings.
  • the 6-minute recrystallization temperature of the Example B wire was found to be significantly higher by approximately 300C than that obtained with the control wire.
  • EXAMPLE C A presintered compact of tungsten containing the same concentration of grain-growth-promoting additives was prepared as described in the previous examples. The compact was immersed in distilled water, and the solvent soaked ingot then placed in an aqueous thorium nitrate solution having a concentration of approximately 520 grams thoria per liter of solution. The liquid diffusion time for this example was 4 hours which provided a thoria concentration gradient in the sintered ingot as reported in Table I above. The sintered compact was processed into 14.6 mil wire in the same manner described in the preceding examples. The approximate thoria concentration gradient in the wire is reported in FIG. 1.
  • Example C wire recrystallizes to a large grain tungsten structure which is sag-resistant.
  • the temperature at which this occurs for 6-minute isochronal anneals is approximately 400C above that for a control wire of the same size containing only the same concentration of the grain-growth-promoting additives but containing no thoria.
  • Very fast heating rates cause a small grain size to develop analogous to that shown in FIG. 3b.
  • a product as in claim 1 wherein the growthpromoting additives comprise potassium, silicon and aluminum compounds.
  • a product as in claim 1 wherein the thoria concentration is at least percent less at the center of the product than at the exterior surface.
  • An electric lamp including an incandescible filament as defined in claim 4.
  • a product as in claim 6 wherein the growthpromoting additives comprise potassium, silicon and aluminum compounds.
  • thoria concentration is at least 10 percent less at the center of the product than at the exterior surface.
  • An electric lamp including an incandescible filament as defined in claim 9.
  • a product as in claim 11 wherein the growthpromoting additives comprise potassium,'silicon and aluminum compounds.
  • ThO concentration is at least 10 percent less at the center of the product than at the exterior surface.
  • An electric lamp including an incandescible filament as defined in claim 13.
  • a porous metal body having an interconnected pore structure of tungsten containing grain-growthpromoting additives which includes thoria particles dispersed in at least a portion of the pores such that a concentration gradient is established with the maximum thoria concentration being located at the exterior sur face portion of said porous body and with said thoria concentration continuously and uniformly diminishing with increasing distance to the interior portion of the porous body so that no sharp compositional variation exist along said concentration gradient.
  • a porous metal body as in claim 16 wherein the growth-promoting additives comprise potassium, silicon and aluminum compounds.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Contacts (AREA)
US00248933A 1972-05-01 1972-05-01 Tungsten alloy products Expired - Lifetime US3802851A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US00248933A US3802851A (en) 1972-05-01 1972-05-01 Tungsten alloy products
GB1313973A GB1407902A (en) 1972-05-01 1973-03-19 Tungsten alloy products
FR7310058A FR2182883B1 (enExample) 1972-05-01 1973-03-21
JP3195373A JPS538288B2 (enExample) 1972-05-01 1973-03-22
DE19732314274 DE2314274C3 (de) 1972-05-01 1973-03-22 Poröser, dispersionsgehärteter Wolframsinterkörper
HUGE938A HU166091B (enExample) 1972-05-01 1973-04-25

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Application Number Priority Date Filing Date Title
US00248933A US3802851A (en) 1972-05-01 1972-05-01 Tungsten alloy products

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US3802851A true US3802851A (en) 1974-04-09

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US00248933A Expired - Lifetime US3802851A (en) 1972-05-01 1972-05-01 Tungsten alloy products

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US (1) US3802851A (enExample)
JP (1) JPS538288B2 (enExample)
FR (1) FR2182883B1 (enExample)
GB (1) GB1407902A (enExample)
HU (1) HU166091B (enExample)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2642757A1 (de) * 1976-08-26 1978-03-02 Bbc Brown Boveri & Cie Verbundwerkstoff
US4097415A (en) * 1975-03-03 1978-06-27 Societe Lignes Telegraphiques Et Telephoniques Production of improved anodes for solid electrolyte capacitors
US4104063A (en) * 1972-11-29 1978-08-01 Schwabische Huttenwerke Gesellschaft Mit Beschrankter Haftung Formed part of sintered iron and method and sintering tile for making same
US4677031A (en) * 1985-04-10 1987-06-30 Nippon Gakki Seizo Kabushiki Kaisha Conductive plate
US5590386A (en) * 1995-07-26 1996-12-31 Osram Sylvania Inc. Method of making an alloy of tungsten and lanthana
US5774780A (en) * 1994-11-27 1998-06-30 Bayerische Metallwerke Gmbh Process for production of a shaped part
US5972069A (en) * 1997-07-24 1999-10-26 Mitsubishi Denki Kabushiki Kaisha Metallic material made from tungsten or molybdenum, method of producing the metallic material, and secondary product material using the metallic material
US6045682A (en) * 1998-03-24 2000-04-04 Enthone-Omi, Inc. Ductility agents for nickel-tungsten alloys
US20060082312A1 (en) * 2004-10-14 2006-04-20 Koito Manufacturing Co., Ltd. Arc tube for discharge lamp

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4104063A (en) * 1972-11-29 1978-08-01 Schwabische Huttenwerke Gesellschaft Mit Beschrankter Haftung Formed part of sintered iron and method and sintering tile for making same
US4156605A (en) * 1972-11-29 1979-05-29 Schwabische Huttenwerke Gesellschaft Mit Beschrankter Haftung Formed part of sintered iron and method and sintering tile for making same
US4097415A (en) * 1975-03-03 1978-06-27 Societe Lignes Telegraphiques Et Telephoniques Production of improved anodes for solid electrolyte capacitors
DE2642757A1 (de) * 1976-08-26 1978-03-02 Bbc Brown Boveri & Cie Verbundwerkstoff
US4314007A (en) * 1976-08-26 1982-02-02 Bbc Brown, Boveri & Company Limited Composite shaped articles
US4677031A (en) * 1985-04-10 1987-06-30 Nippon Gakki Seizo Kabushiki Kaisha Conductive plate
US5774780A (en) * 1994-11-27 1998-06-30 Bayerische Metallwerke Gmbh Process for production of a shaped part
US5590386A (en) * 1995-07-26 1996-12-31 Osram Sylvania Inc. Method of making an alloy of tungsten and lanthana
US5972069A (en) * 1997-07-24 1999-10-26 Mitsubishi Denki Kabushiki Kaisha Metallic material made from tungsten or molybdenum, method of producing the metallic material, and secondary product material using the metallic material
US6045682A (en) * 1998-03-24 2000-04-04 Enthone-Omi, Inc. Ductility agents for nickel-tungsten alloys
US20060082312A1 (en) * 2004-10-14 2006-04-20 Koito Manufacturing Co., Ltd. Arc tube for discharge lamp
US7443100B2 (en) * 2004-10-14 2008-10-28 Koito Manufacturing Co., Ltd. ARC tube discharge lamp with compression strain layer

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Publication number Publication date
GB1407902A (en) 1975-10-01
JPS538288B2 (enExample) 1978-03-27
FR2182883A1 (enExample) 1973-12-14
FR2182883B1 (enExample) 1976-05-07
HU166091B (enExample) 1975-01-28
JPS4922315A (enExample) 1974-02-27
DE2314274A1 (de) 1973-11-15
DE2314274B2 (de) 1977-06-23

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