US2095105A - Process of treating metal surfaces - Google Patents

Process of treating metal surfaces Download PDF

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Publication number
US2095105A
US2095105A US43021A US4302135A US2095105A US 2095105 A US2095105 A US 2095105A US 43021 A US43021 A US 43021A US 4302135 A US4302135 A US 4302135A US 2095105 A US2095105 A US 2095105A
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US
United States
Prior art keywords
metal
filament
tungsten
temperature
compound
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.)
Expired - Lifetime
Application number
US43021A
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English (en)
Inventor
Henry M Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
Original Assignee
General Electric Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US43021A priority Critical patent/US2095105A/en
Priority to DEP73562D priority patent/DE655753C/de
Application granted granted Critical
Publication of US2095105A publication Critical patent/US2095105A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K3/00—Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof
    • H01K3/02—Manufacture of incandescent bodies
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9335—Product by special process
    • Y10S428/938—Vapor deposition or gas diffusion

Definitions

  • My invention relates to a process for treating metal surfaces to give them increased smoothness and uniformity, and more particularly to a process for polishing filamentary heating members for use in lamps and electric discharge devices.
  • the temperature at which a tungsten filament for a lamp, vacuum tube, or similar discharge device, will operate for a given filament current is dependent in part upon the condition of the a surface of the wire. In general, the smoother the surfaceof the wire, the higher will be the temperature at which it will operate in vacuum for a, given diameter and filament current. Since the electron emission of a filament is extremely sensitive to variations in its operating temperature, it is of great importance in electric discharge devices that the filament temperature shall not fall below its designed value because of imperfections in the material used. Furthermore, to satisfy the commercial requirements it is essential that the method of treatment adopted to obtain this result be such as to insure a highly uniform product.
  • an object of my present invention to provide a method of smoothing tungsten filaments and other metal surfaces which will cause no decrease in the dimensions or material content -of.the object treated.
  • the high temperature stipulated above may be obtained by impressing on the filament terminals a suitablepotential from a source 5 of direct or alternating current. Regulation of the magnitude of the impressed voltage may be achieved by an appropriate adjusting circuit exemplified in the present instance as a potentiometer connection 6 cooperating with a resistance .I shunted across the terminals of the voltage source. At the temperature stated the cleaning operation ordinarily will require only a very short time, not in excess of 3 or 4 seconds.
  • valves 8 and 9 are adjusted so that the former is open and the latter closed so as to cause the hydrogen stream to pass over the surface 9 of a quantity of volatile hydrocarbon, such as benzol, contained in the tank ID.
  • a s'uflicient quantity of the benzol will be retained by the hydrogen to supply an adequate carbon-containing atmosphere for the dome 2.
  • the amount of hydrocarbon transmitted may be regulated invariou's ways as by adjusting the level of the liquid surface 9' with respect to the tubu-' lar orifice II.
  • the carbonizatlon step is carried out with the filament at a temperature of from about.1200 to about 1500 C., this factor being regulated as above explained by adjustment of the potential impressed on the filament I.
  • the carbonization process will result in the production of the various carbides of tungstenon the filament surface. In'so far as .the nature of such carbides is essential'to the purposes of my invention, they are characterized by having melting points as low as 2777 and 2877 C. as compared with 3370" 0., the melting point of tungsten.
  • the valve 9 may be opened and the valve 8 closed, so that the filament is again immersed in a pure hydrogen atmosphere.
  • the temperature may be raised to a point between the melting point of tungsten carbide and that of the tungsten core.
  • the carbide coating becomes fused and will flow over the base metal so as to form a perfectly uniform. and smooth surface. I have found thatfour heating periods of from to 1 second each are adequate toobtain a good smoothing effect. It is possible, however, to obtain a somewhat greater consistency of results by repeating the carbonizing and melting operations one or more times.
  • the filament surface may be completely decarbonized by continued flashing in hydrogen at a temperature approaching that of tungstens melting point.
  • the removal of the carbon results in the restoration of a pure tungsten surface modified only to the extent of having all irregularities and variations eliminated.
  • the preliminary steps may be carried out by causing a layer of the sulphides or phosphides of the metal in question to be formed on the surface under treatment.
  • the sulphide layer it is possible to use an atmosphere such as a mixture of hydrogen and hydrogen sulphide, while the phosphide coatings may be procured by the use of a hydrogenphospho'rus compound such as phosphine.
  • 5 layers thus formed may be reconverted to the base metal by being subjected to the reducing action of hydrogen at an elevated temperature as previously explained. Since both the coating compounds mentioned have a lower melting point than the metals themselves, it will be seen that they are amenable to the smoothing treatment described. It is only essential that the melted material have a surface tension and coemcient ofadhesionsuchastoinsurethatitwillwet or flow evenly over the surface of the metal to be polished.
  • the method of smoothing a metal surface which comprises forming on said surface a compound of said metal having a lower melting pointthan the metal itself, heating said compound to a temperature intermediate between the melting points of said compound and said metal and thereafter chemically reconverting said compound to said metal.
  • the method of smoothing a tungsten surface which comprises forming on said surface a tungsten compound having a lower melting point than tlmgsten itself, heating said compound to a temperature, intermediate between the melting points of tungsten and of said compound, and thereafter chemically reconverting said compound to tungsten.
  • the method of smoothing a tungsten surface which comprises forming tungsten carbide on said surface, heating said surface to a temperature between about 2800 andabout 3300 C. thereby to cause said carbide to fiow evenly over said surface and thereafter chemically converting said tungsten carbide to tungsten.
  • the method of smoothing a metal surface which comprises forming on said surface a substance having said metal as an ingredient thereof and having a lower melting point than the metal itself, heating said substance to a temperature intermediate between the melting points of said metal and said substance thereby to cause the substance to fiow evenly over said surface and thereafter bringing said surface into contact with an atmosphere eflective to reconvert saidv 1 substance to said metal.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
US43021A 1935-10-01 1935-10-01 Process of treating metal surfaces Expired - Lifetime US2095105A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US43021A US2095105A (en) 1935-10-01 1935-10-01 Process of treating metal surfaces
DEP73562D DE655753C (de) 1935-10-01 1936-07-23 Verfahren zum Egalisieren von duennen, drahtfoermigen oder bandfoermigen Gluehkoerpern und Heizkoerpern elektrischer Gluehlampen und Entladungsgefaesse

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US43021A US2095105A (en) 1935-10-01 1935-10-01 Process of treating metal surfaces

Publications (1)

Publication Number Publication Date
US2095105A true US2095105A (en) 1937-10-05

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ID=21925027

Family Applications (1)

Application Number Title Priority Date Filing Date
US43021A Expired - Lifetime US2095105A (en) 1935-10-01 1935-10-01 Process of treating metal surfaces

Country Status (2)

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US (1) US2095105A (de)
DE (1) DE655753C (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2450007A (en) * 1942-11-23 1948-09-28 Standard Telephones Cables Ltd Carburized filament and method for treating the same
US2465864A (en) * 1943-06-22 1949-03-29 Westinghouse Electric Corp Automatic carbonization of filaments

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2450007A (en) * 1942-11-23 1948-09-28 Standard Telephones Cables Ltd Carburized filament and method for treating the same
US2465864A (en) * 1943-06-22 1949-03-29 Westinghouse Electric Corp Automatic carbonization of filaments

Also Published As

Publication number Publication date
DE655753C (de) 1938-01-22

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