EP0250511A1 - Electrode a courant eleve - Google Patents

Electrode a courant eleve

Info

Publication number
EP0250511A1
EP0250511A1 EP87900130A EP87900130A EP0250511A1 EP 0250511 A1 EP0250511 A1 EP 0250511A1 EP 87900130 A EP87900130 A EP 87900130A EP 87900130 A EP87900130 A EP 87900130A EP 0250511 A1 EP0250511 A1 EP 0250511A1
Authority
EP
European Patent Office
Prior art keywords
coating
current electrode
zro
tho
ceo
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Withdrawn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
EP87900130A
Other languages
German (de)
English (en)
Inventor
Kuno Kirner
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.)
Plasmainvent AG
Original Assignee
Plasmainvent AG
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 Plasmainvent AG filed Critical Plasmainvent AG
Publication of EP0250511A1 publication Critical patent/EP0250511A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0205—Non-consumable electrodes; C-electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/24—Features related to electrodes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3478—Geometrical details

Definitions

  • the invention relates to a high-current electrode made of a material which is a good conductor of heat and electricity and which is high-melting at least on the surface of the electrode and has a low electron work function, in particular for use in plasma torches.
  • Such high-current electrodes are used, in addition to plasma torches, for example in high-current arc light sources, in high-current arc melting furnaces and in welding processes and equipment in which electrical currents are used
  • the requirements for such electrodes are good high-temperature behavior, i.e. high melting point, high boiling point and sufficient strength close to the melting point, furthermore good electrical conductivity and high erosion resistance.
  • the high erosion resistance leads to a long service life of the electrode.
  • tungsten is a preferred electrode material for such high-current electrodes.
  • High-current electrodes of the type described at the outset are known, which consist of tungsten and whose service life is improved by additions of ThO 2 .
  • the ThO 2 additives also make it easier to ignite the arc and result in a more stable, quieter arc than pure tungsten electrodes. This is due to the low electron work function Wa of ThO 2 (1.6 to 3 eV).
  • the relatively high electron work function Wa of tungsten (4.5 eV) is reduced, for example, by adding 2% ThO 2 to approximately 2.63 to 2.86 eV.
  • ThO 2 additives are from
  • Tungsten electrode is about 4% by weight.
  • the invention has for its object to provide a high-current electrode of the type described, which strength due to high Abbrandf a much larger
  • the electrode base body has a coating which is high-melting and has a low electron work function.
  • the electrode base body can be made of tungsten, molybdenum, copper or another good heat and current conductive material and also have a hollow shape that is easy to cool.
  • the coating is expediently applied in a plasma spraying process.
  • the coating advantageously consists of W and at least 4% by weight of ThO 2 or CeO 2 .
  • the coating consists of W and about 10% by weight of ThO 2 or CeO 2 .
  • the coating can also consist of W and CeO 2 in a ratio of 1: 1.
  • the coating consists of W and at least 1% by weight of LaB 6 or Y 2 O 3 .
  • the coating can advantageously consist of W and at least 1% by weight of oxides, carbides, borides with high
  • CeS 6 , ThB 6 , HfB 6 , CeB 6 , SrB 6 and CeB 12 exist.
  • the electrode base body is a hollow body which is internally coolant-cooled during operation.
  • the materials of the coating are sprayed onto a core in a thickness that, after dissolving or unscrewing the core, results in a self-supporting high-current electrode from the injection molding machine.
  • the materials of the coating are advantageously applied in a graded manner, i.e. the concentration of the addition to W is specifically changed, preferably towards the surface.
  • a wettable powder mixture for coating a high-current electrode in the plasma spray process is characterized in that it consists of W and at least 4% by weight of ThO 2 or CeO 2 . It can advantageously consist of W and about 10% by weight of ThO 2 or CeO 2 , in the case of CeO 2 the ratio between W and CeO 2 can be 1: 1.
  • Another spray powder mixture for coating a high-current electrode in the plasma spray process is characterized in that it consists of W and at least 1% by weight of LaB 6 or Y 2 O 3 .
  • another wettable powder mixture for coating a high-current electrode in the plasma spray process is characterized in that it consists of W and at least 1% by weight of oxides, carbides, borides with a high melting temperature and low electron work function, such as Thc 2 , HfC, UC2, SrO 2 , BaO, CaO, La 2 O 3 , LaCrO 3 , HfO 2 , Yb 2 O 3 , ZrO 2 ,
  • BaO.ThO 2 CaO.HfO 2 , BaO.ZrO 2 , SrO 2 .ZrO 2 , ThO 2 .ZrO 2 ,
  • the coating of W and the additives mentioned which lower the electron work function of W, can be applied to electrode bases, for example made of pure tungsten, copper, molybdenum or the like, in any thickness.
  • the upper limit of the additive is due to the requirement for good electrical conductivity and the impairment of the
  • Flow behavior of the tungsten powder given by the additives during plasma spraying The flow behavior depends on the grain size.
  • the grain size of the additional powder is advantageously matched to the grain size of the UV powder in such a way that the liquidification of the two components takes place at about the same time in the plasma jet.
  • the grain size of the W powder is advantageously about -44 + 5.6 ⁇ m, while the grain size of the additional powder is in the range of the grain size of the W powder or above.
  • the larger grain size of the additional powder is particularly suitable for additional powder with a significantly lower melting temperature than that of W.
  • the grain size of the CeO 2 powder can advantageously be approximately -105 + 44 ⁇ m.
  • the thickness of the coating depends on the electrical load and the thermal conditions of the high-current electrode.
  • cathodes which are used at average currents of 500 A, for example, thicknesses of 0.5 mm are sufficient, but thicknesses of 1 to 2 mm are preferably applied.
  • the current strength of cathodes according to the invention is much higher than that of conventional cathodes, for example at 1000 A practically no material loss and thus no decrease in the electrode length.
  • Fig. 2 conventional sintered tungsten electrodes before
  • Fig. 3 embodiments of the high-current electrodes coated according to the invention before use and after use in a plasma torch.
  • the electrode 1 shows a cross section through an embodiment of a high-current electrode 1 coated according to the invention.
  • the electrode 1 consists of a hollow electrode base body 2, which consists of tungsten, molybdenum, copper or another material which is a good conductor of heat and electricity.
  • a coating 3 made of tungsten and an additive described in more detail below, which is applied in the plasma spraying process. Coolant can be supplied to this electrode as indicated by the arrow K.
  • the coating materials can if necessary applied in a graded manner, ie the concentration of the addition to W can be changed in a targeted manner, preferably increased towards the surface.
  • FIG. 2 shows conventional stick electrodes 1, FIG. 2a showing the initial shape of a sintered tungsten electrode.
  • 2b shows a pure tungsten electrode after loading with 500 A. This clearly shows an erosion, including deformation of the electrode, which is not particularly useful for plasma spraying technology.
  • 2c shows a sintered electrode, the electrode body of which consists of W + 2% by weight ThO 2 , specifically after operation at 1000 A. Here too, considerable electrode erosion can be seen
  • 3 shows a number of high-current electrodes with a coating according to the invention.
  • 3a shows the initial shape of a high-current electrode 1 with woifram core in the form of an electrode base body 2 and coating 3 applied to the front of the electrode.
  • 3b shows such an electrode with a coating 3 of W + 10% by weight ThO 2 after operation at 1000 A.
  • the erosion is slight and tolerable.
  • 3c shows such an electrode 1 with a coating 3 of W + 10% by weight CeO 2 , likewise after operation at 1000 A.
  • the erosion of the electrode 1 can hardly be seen here.
  • FIG. 3d shows the initial shape of a high-flow electrode 1 with a hollow, water-cooled copper core as the main electrode body 2 and with a coating 3 made of W + 10% by weight CeO 2 .
  • the same electrode 1 is after one Load shown with 1000 A. It can be clearly seen that there is practically no electrode erosion at all.
  • the cathodes or electrodes 1 according to the invention can be subjected to a much higher current intensity than conventional cathodes as shown in FIG. 2, given the same starting conditions, ie the same outer contour, the same gas flow and the same cooling.
  • S is the emission current density
  • Wa is the electron Work function
  • a R a material constant
  • T the absolute temperature in the emission range
  • k the Boltzmann constant.
  • the emission current density S increases by a factor of 2.5 at an emission temperature of, for example, approximately 3700 ° K at W with a Wa reduction from 5 eV to two 2 eV.
  • Electrode particles in the layer affects in a higher insulation and dielectric strength; With some corrosion protection layers, the lowest possible foreign content in the form of inclusions is important. Even when encapsulating implants to improve their wax-in, no foreign particles should be injected.
  • the coating 3 of the high-current electrodes 1 described in connection with FIGS. 1 and 3 was applied in a plasma spraying process.
  • the wettable powder consisted of tungsten with the additives explained below, which reduce the electron work function of tungsten.
  • the electrode base body consisted, for example, of pure tungsten, copper, molybdenum and the like, the coating 3 being applied in any thickness in the preferred plasma spraying process.
  • a powder mixture consisting of tungsten + x% by weight additive is sprayed on.
  • the additives are preferably ThO 2 or CeO 2 , each with x> 4 and x ⁇ 10.
  • a mixture of W and CeO 2 in a ratio of 1: 1 for the coating 3 is also a suitable embodiment.
  • carbides, borides with a high melting temperature and low electron work function such as ThC 2 , HfC, UC 2 , SrO 2 , BaO, CaO, La 2 O 3 , LaCrO 3 , HfO 2 , Yb 2 O 3 , ZrO 2 , mixed oxides from this group, BaO.ThO 2 , CaO.HfO 2 , BaO.ZrO 2 , SrO 2 .ZrO 2 , ThO 2 .ZrO 2 , CaO.ZrO 2 and CeB 6 , ThB 6 , HfB 6 , CeB 6 , SrB 6 and C eB 1 2 is x> 1.
  • the grain size of the additive powder to the grain size of the W powder is expediently coordinated in such a way that the two components liquefy in the plasma jet takes place at approximately the same time.
  • the upper limit of x is given by the requirement for good electrical conductivity and by the impairment of the flow behavior of the Woiframouiver by the additives; the latter in turn depends on the particle size of the wettable powder.
  • the grain size of the additional powder is preferably selected in the range of the grain size of the tungsten powder. Powders with the grain size proved to be very suitable -44 + 5.6 ⁇ m, whereby additional powder with a much lower melting temperature than tungsten should be coarser than the tungsten powder.
  • a suitable grain size for CeO 2 powder is around -105 + 44 ⁇ m.
  • the thickness of the coating 3 depends on the electrical load and the thermal conditions of the high-current electrode 1.
  • thicknesses of 0.5 mm are sufficient, preferably thicknesses of 1 to 2 mm are applied.
  • Another limit, which is given by electrode wear that is too rapid, relates to the addition of hydrogen to the plasma during plasma spraying. Due to the higher thermal conductivity of the hydrogen plasma and the extreme voltage rise when hydrogen is added, the proportion in argon / hydrogen mixtures must be kept below 25%.
  • the high-current electrodes described make it much easier to spray materials that are difficult to spray - either in terms of melting behavior or grain size.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Geometry (AREA)
  • Coating By Spraying Or Casting (AREA)

Abstract

L'électrode à courant élevé (1), qui est réalisée à partir d'un matériau ayant une bonne conductibilité thermique et électrique, est enrobée d'un revêtement (3) pour réduire la perte par combustion du matériau du corps (2) de l'électrode, ledit revêtement fondant à une température élevée et possédant une faible affinité pour les électrons. Le revêtement (3) est appliqué de préférence au moyen du procédé de dépôt par projection au plasma. Le mélange de poudre de projection pour le revêtement (3) comporte de préférence W et au moins 4 % en poids de Th02 ou de Ce0, ou bien W et au moins 1 % en poids d'oxydes, carbures, borures caractérisés par une température de fusion élevée et un faible travail de sortie des électrons.
EP87900130A 1985-12-17 1986-12-17 Electrode a courant eleve Withdrawn EP0250511A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3544657 1985-12-17
DE19853544657 DE3544657A1 (de) 1985-12-17 1985-12-17 Hochstromelektrode

Publications (1)

Publication Number Publication Date
EP0250511A1 true EP0250511A1 (fr) 1988-01-07

Family

ID=6288675

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87900130A Withdrawn EP0250511A1 (fr) 1985-12-17 1986-12-17 Electrode a courant eleve

Country Status (3)

Country Link
EP (1) EP0250511A1 (fr)
DE (1) DE3544657A1 (fr)
WO (1) WO1987004039A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4105407A1 (de) * 1991-02-21 1992-08-27 Plasma Technik Ag Plasmaspritzgeraet zum verspruehen von festem, pulverfoermigem oder gasfoermigem material
DE4122756A1 (de) * 1991-07-10 1993-02-11 Erno Raumfahrttechnik Gmbh Triebwerk fuer raumflugkoerper
DE19626941A1 (de) * 1996-07-04 1998-01-08 Castolin Sa Verfahren zum Beschichten oder Schweißen leicht oxidierbarer Werkstoffe sowie Plasmabrenner dafür
DE19707699C1 (de) * 1997-02-26 1998-07-23 Oliver Dr Ing Prause Plasmabrenner für Plasmaspritzanlagen
DE19900477A1 (de) * 1999-01-08 2000-07-13 Linde Tech Gase Gmbh Thermisches Schneiden und Schweißen mit Verschleißschutz

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB750632A (en) * 1952-11-13 1956-06-20 Union Carbide & Carbon Corp Improvements in refractory metal electrodes for use in inert gas-shield welding and cutting apparatus
BE573489A (fr) * 1957-12-03 1959-04-01 Union Carbide Corp Objet manufacturé recouvert d'une couche ou se composant de matières réfractaires pures.
FR1421353A (fr) * 1964-08-19 1965-12-17 Saint Gobain Perfectionnements aux électrodes réfractaires pour arcs électriques de forte intensité
US3515839A (en) * 1967-04-07 1970-06-02 Hitachi Ltd Plasma torch
CH487698A (de) * 1968-02-23 1970-03-31 Siemens Ag Nichtabschmelzende Elektrode für Lichtbögen kleiner Leistung
FR2187492A1 (en) * 1972-06-05 1974-01-18 Riou Andre Refractory welding electrode - for inert gas shielded welding
US3941903A (en) * 1972-11-17 1976-03-02 Union Carbide Corporation Wear-resistant bearing material and a process for making it
DE2755213C2 (de) * 1977-12-10 1982-05-06 Fa. Dr. Eugen Dürrwächter DODUCO, 7530 Pforzheim Nichtabschmelzende Elektrode und Verfahren zu ihrer Herstellung

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8704039A1 *

Also Published As

Publication number Publication date
WO1987004039A1 (fr) 1987-07-02
DE3544657A1 (de) 1987-06-19

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Inventor name: KIRNER, KUNO