US3597649A - Device for plasma-arc treatment of materials - Google Patents

Device for plasma-arc treatment of materials Download PDF

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Publication number
US3597649A
US3597649A US798348A US3597649DA US3597649A US 3597649 A US3597649 A US 3597649A US 798348 A US798348 A US 798348A US 3597649D A US3597649D A US 3597649DA US 3597649 A US3597649 A US 3597649A
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cathode
plasma
arc
hafnium
central nozzle
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US798348A
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David Grigorievich Bykhovsky
Alexandr Yakovlevich Medvedev
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    • 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
    • B23K10/00—Welding or cutting by means of a plasma
    • 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
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/222—Non-consumable 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
    • H05H1/3436—Hollow cathodes with internal coolant flow
    • 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
    • H05H1/3442—Cathodes with inserted tip

Definitions

  • the device can also be employed for surface fusion, for example for the removal of a defective surface layer from castings and cast products or for the correction of such local defects as cracks, pits, scabs.
  • the invention can also be used for heating chemically active gases and their mixtures and for the thermochemical surface treatment of metal, e.g. nitriding, casehardening and similar processes.
  • the present invention can be used both with and without additional protection of the cathode assembly.
  • a device for plasma-arc treatment of materials in active media comprising a cathode secured in a cooled cathode holder.
  • the latter is connected by an insulating bushing with a body which If a number of nozzles are used, they are separated by an insulating gasket 12 (shown by dotted lines in the drawing).
  • the coolant may be either water or gas.
  • the body has a hole 13 for the supply of plasma-generating gas, e.g. air, nitrogen, oxygen or mixtures of gases containing nitrogen or oxygen.
  • the cathode 14 made of a metal forming chemical compounds with the components of the medium. These compounds should have the following properties. They should form a 0 high-melting film of, say, oxides, nitrides or carbides on the accommodates cooled nozzles with central passages intended to stabilize the arc discharge.
  • the cathode is made of a metal producing chemical compounds with the components of the medium. Such metals are zirconium, lanthanum, strontium, yttrium, thorium and their alloys, as seen in US. Pat. No. 3,198,932.
  • the above-described cathode has a short service life, in fact not over 4 hours at are currents of 300 A.
  • the known cathode is insufficiently stable in operation.
  • An object of the present invention is .to eliminate the aforesaid disadvantages.
  • the main object of the present invention is to provide a device for plasma treatment of materials in active media, preferably for cutting metals, whose cathode will last beyond a minimum value or will practically not wear out at all at are currents of 300 A.
  • the device should give stable service at are currents above 300 A., and the cathode service life should be well over 4 hrs. at-currents exceeding 300 A.
  • This object is accomplished by providing a'device for plasma-arc treatment of materials in active media, preferably for cutting metals wherein the cathode is made of a metal producing chemical compounds with the components of the medium.
  • a metal is hafnium (Hf).
  • the device for plasma-arc cutting of metals in active media consists of a body I accommodating a cathode holder 2 anda nozzle 3 with a central passage 4 intended to stabilize the are discharge 5.
  • the cathode holder 2 is fastened in the body I by means of the insulating bushing 8 and cooled by the coolant supplied through a pipe 9 installed inside the cathode holder 2.
  • the nozzles 3 and 7 have passages 10 and 1! for the supply of coolant.
  • these compounds would be characterized by high values of thermionic emission, Le. a low work function of electrons. Moreover, these compounds should exhibit high stability under the conditions of repeated heating and cooling.
  • hafnium was selected for the cathode because, when reacting with the oxygen, nitrogen and carbon contained in the plasma-generating gas, it is covered with a film on the working surface consisting of highmelting oxides, nitrides or carbides of hafnium. This film has a low work function of electrons.
  • the structure and the thermal and physical characteristics of the film hamper the further reactive diffusion of the active components of the plasma-generating medium, stopping it altogether in some cases.
  • This phenomenon makes it possible to considerably prolong the life of the cathode and to increase the working current above 300 A.
  • the cathode holder 2 of the device is under negative potential while the work 6 is under positive potential.
  • the are discharge 5 burns between the cathode l4 and the work 6, passing through the stabilizing passage 4 of the nozzle 3. If the additional nozzle 7 is used, the discharge 5 also passes through the stabilizing passage 15 of the nozzle 7. In such a case the nozzles 3 and 7 are installed so as to align the axes of the cathode 14 with those ofthe passages 4 and 15.
  • the active gas enters the device through the hole 13 and passes, together with the arc discharge 5, through the passages 4 and 15.
  • hafnium (Hf) cathode After the above-described device with a hafnium (Hf) cathode has been tested by cutting low-carbon steels in the air it has been established that the hafnium cathode suffers practically no wear at are currents of up to 400 A. At arc currents exceeding 400 A. the operational life of the cathode amounted to 10-16 hrs.
  • Hf hafnium
  • a plasma-arc device for treating material in an active medium having a central cathode holder and cathode, an annular passageway between the cathode holder and a housing, plasma-generating gas inlet means to the annular passageway, at least one central nozzle between the cathode and a workpiece, and a power source
  • said cathode is made of hafnium
  • the are discharge between said cathode and the workpiece is stabilized by the plasmagenerating gas passing concentric the cathode axis through the central nozzle and said cathode reacts with the active components in the plasma-generating gas to form a high-melting film on its working surface, which film has a low work function and substantially increases the life of said cathode.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mechanical Engineering (AREA)
  • Plasma Technology (AREA)
  • Arc Welding In General (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

A device for plasma-arc treatment of materials in active media wherein the cathode is made of hafnium which extends the service life of the cathode.

Description

5, by Walter H.
pages 532 534, Reinade of hafnium which References Cited UNITED STATES PATENTS gham.. OTHER REFERENCES iques for Electron Tube plasma-arc treatment of materials 2/1953 Deri 8/1965 Weatherly...........l........
, section entitled Hafnium" on H0lj 17/04 313/231,
ngrad,
inventors David Grigorievich Bykhovsky Konjushenny pereulok. 1/6, kv. l8; Alexandr Yakovlevich Medvedev, ulitsa Kalyaeva, 3, kv. 4, both of Leni U.S.S.R. Appl. No. 798,348 [22] Filed Feb. 11, 1969 [45] Patented Aug. 3, 1971 Feb. 15, 1968 U.S.S.R. 1,218,055
-ARC TREATMENT OF MATERIALS 3 Claims, 1 Drawing Fig. [52] 11.8. 219/145. 313/231, 313/31 Field of 311,211;219/145,75, 121
United States Patent [32] Priority [54] DEVICE FOR PLASMA DEVICE FOR PLASMA-ARC TREATMENT OF MATERIALS The present invention relates to devices for plasma-arc treatment of materials and more particularly it relates to devices for plasma-arc treatment of materials in active media, preferably for plasma-arc cuttingof metals.
The device can also be employed for surface fusion, for example for the removal of a defective surface layer from castings and cast products or for the correction of such local defects as cracks, pits, scabs.
The invention can also be used for heating chemically active gases and their mixtures and for the thermochemical surface treatment of metal, e.g. nitriding, casehardening and similar processes.
The present invention can be used both with and without additional protection of the cathode assembly.
Known in the art is a device for plasma-arc treatment of materials in active media, preferably for cutting metals, comprising a cathode secured in a cooled cathode holder. The latter is connected by an insulating bushing with a body which If a number of nozzles are used, they are separated by an insulating gasket 12 (shown by dotted lines in the drawing). The coolant may be either water or gas. The body has a hole 13 for the supply of plasma-generating gas, e.g. air, nitrogen, oxygen or mixtures of gases containing nitrogen or oxygen.
Press fitted into the cathode holder 2, flush with it, is the cathode 14 made of a metal forming chemical compounds with the components of the medium. These compounds should have the following properties. They should form a 0 high-melting film of, say, oxides, nitrides or carbides on the accommodates cooled nozzles with central passages intended to stabilize the arc discharge. The cathode is made of a metal producing chemical compounds with the components of the medium. Such metals are zirconium, lanthanum, strontium, yttrium, thorium and their alloys, as seen in US. Pat. No. 3,198,932.
However, the employment of the above-described device is limited by the following disadvantages of the cathode, or the material it is made of.
The above-described cathode has a short service life, in fact not over 4 hours at are currents of 300 A.
At arc currents exceeding 300 A., wear of the cathode becomes so rapid that it becomes practically impossible to utilize such a cathode.
Furthermore, the known cathode is insufficiently stable in operation.
An object of the present invention is .to eliminate the aforesaid disadvantages. I
The main object of the present invention is to provide a device for plasma treatment of materials in active media, preferably for cutting metals, whose cathode will last beyond a minimum value or will practically not wear out at all at are currents of 300 A. The device should give stable service at are currents above 300 A., and the cathode service life should be well over 4 hrs. at-currents exceeding 300 A.
This object is accomplished by providing a'device for plasma-arc treatment of materials in active media, preferably for cutting metals wherein the cathode is made of a metal producing chemical compounds with the components of the medium. According to the invention, such a metal is hafnium (Hf).
Given below is a detailed description of the device by way of example with reference to the accompanying drawing of a preferred embodiment which shows schematically a longitudinal section through the device for plasma-arc cutting of metals in an active medium.
The device for plasma-arc cutting of metals in active media consists of a body I accommodating a cathode holder 2 anda nozzle 3 with a central passage 4 intended to stabilize the are discharge 5.
To prevent the formation of a double are in case the nozzle 3 comes accidentally in contact with the work 6, or to increase the total length of the stabilizing passage 4, there may be installed at least one more nozzle 7 (shown by dotted lines in the drawing). I
The cathode holder 2 is fastened in the body I by means of the insulating bushing 8 and cooled by the coolant supplied through a pipe 9 installed inside the cathode holder 2. The nozzles 3 and 7 have passages 10 and 1! for the supply of coolant.
working surface of the cathode 14. In addition, these compounds would be characterized by high values of thermionic emission, Le. a low work function of electrons. Moreover, these compounds should exhibit high stability under the conditions of repeated heating and cooling.
In accordance with the invention, hafnium was selected for the cathode because, when reacting with the oxygen, nitrogen and carbon contained in the plasma-generating gas, it is covered with a film on the working surface consisting of highmelting oxides, nitrides or carbides of hafnium. This film has a low work function of electrons.
Besides, the structure and the thermal and physical characteristics of the film hamper the further reactive diffusion of the active components of the plasma-generating medium, stopping it altogether in some cases.
This phenomenon makes it possible to considerably prolong the life of the cathode and to increase the working current above 300 A.
The cathode holder 2 of the device is under negative potential while the work 6 is under positive potential. The are discharge 5 burns between the cathode l4 and the work 6, passing through the stabilizing passage 4 of the nozzle 3. If the additional nozzle 7 is used, the discharge 5 also passes through the stabilizing passage 15 of the nozzle 7. In such a case the nozzles 3 and 7 are installed so as to align the axes of the cathode 14 with those ofthe passages 4 and 15.
The active gas enters the device through the hole 13 and passes, together with the arc discharge 5, through the passages 4 and 15.
After the above-described device with a hafnium (Hf) cathode has been tested by cutting low-carbon steels in the air it has been established that the hafnium cathode suffers practically no wear at are currents of up to 400 A. At arc currents exceeding 400 A. the operational life of the cathode amounted to 10-16 hrs.
The use of the service currents of 400 A. and higher has made it possible to increase the cutting speed of low carbon steel l,52 times as compared with the speeds attainable now.
We claim:
1. In a plasma-arc device for treating material in an active medium having a central cathode holder and cathode, an annular passageway between the cathode holder and a housing, plasma-generating gas inlet means to the annular passageway, at least one central nozzle between the cathode and a workpiece, and a power source, the improvement consisting in that I said cathode is made of hafnium, the are discharge between said cathode and the workpiece is stabilized by the plasmagenerating gas passing concentric the cathode axis through the central nozzle and said cathode reacts with the active components in the plasma-generating gas to form a high-melting film on its working surface, which film has a low work function and substantially increases the life of said cathode.
2. A plasma-arc device as claimed in claim 1 wherein said central nozzle is electrically insulated from said cathode and said cathode holder and central nozzle have coolant passages therein.
3. A plasma-arc device as claimed in claim 1 wherein said reactive components in the plasma-generating gas are selected from a group consisting of oxygen, nitrogen or carbon and said high-melting film is formed of a compound selected from the group consisting of oxides, nitrides or carbides of hafnium.

Claims (3)

1. In a plasma-arc device for treating material in an active medium having a central cathode holder and cathode, an annular passageway between the cathode holder and a housing, plasmagenerating gas inlet means to the annular passageway, at least one central nozzle between the cathode and a workpiece, and a power source, the improvement consisting in that said cathode is made of hafnium, the arc discharge between said cathode and the workpiece is stabilized by the plasma-generating gas passing concentric the cathode axis through the central nozzle and said cathode reacts with the active components in the plasmagenerating gas to form a high-melting film on itS working surface, which film has a low work function and substantially increases the life of said cathode.
2. A plasma-arc device as claimed in claim 1 wherein said central nozzle is electrically insulated from said cathode and said cathode holder and central nozzle have coolant passages therein.
3. A plasma-arc device as claimed in claim 1 wherein said reactive components in the plasma-generating gas are selected from a group consisting of oxygen, nitrogen or carbon and said high-melting film is formed of a compound selected from the group consisting of oxides, nitrides or carbides of hafnium.
US798348A 1968-02-15 1969-02-11 Device for plasma-arc treatment of materials Expired - Lifetime US3597649A (en)

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SU1218055A SU287214A1 (en) 1968-02-15 DEVICE FOR PLASMA TREATMENT OF METALS

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SE (1) SE343497B (en)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3743955A (en) * 1971-07-13 1973-07-03 Us Air Force Radiation hardening read preamplifier
US3930139A (en) * 1974-05-28 1975-12-30 David Grigorievich Bykhovsky Nonconsumable electrode for oxygen arc working
US3976853A (en) * 1973-06-20 1976-08-24 Siemens Aktiengesellschaft Non-fusible electrode, in particular for tungsten inert gas welding and a process for the production thereof
US4027134A (en) * 1973-11-12 1977-05-31 Tokyo Shibaura Electric Co., Ltd. Electrode for electrical discharge machining
US4229873A (en) * 1978-09-15 1980-10-28 Bykhovskij David G Method of producing nonconsumable electrode for use in arc techniques
DE2932930A1 (en) * 1979-08-14 1981-03-26 Gosudarstvennyj proektnyj i naučno-issledovatel'skij institut nikelevo-kobaltovoj i olovjannoj promyšlennosti, St. Petersburg Rapid inspection of non-consumable rod electrodes - by brief use in plasma torch using plasma gas contg. carbon cpds., followed by visual examination of electrode
US4304984A (en) * 1978-05-11 1981-12-08 Bolotnikov Arkady L Non-consumable electrode for plasma-arc welding
US4581516A (en) * 1983-07-20 1986-04-08 Thermal Dynamics Corporation Plasma torch with a common gas source for the plasma and for the secondary gas flows
DE3618600A1 (en) * 1985-06-05 1986-12-11 AGA AB, Lidingö ELECTRODE FOR PLASMA SHEET PROCESSING
EP0390998A1 (en) * 1989-04-03 1990-10-10 ESAB Welding Products, Inc. Method and apparatus for low voltage plasma arc cutting
US5023425A (en) * 1990-01-17 1991-06-11 Esab Welding Products, Inc. Electrode for plasma arc torch and method of fabricating same
EP0465109A2 (en) * 1990-06-26 1992-01-08 Daihen Corporation Electrode for use in plasma arc working torch
US5097111A (en) * 1990-01-17 1992-03-17 Esab Welding Products, Inc. Electrode for plasma arc torch and method of fabricating same
US5208441A (en) * 1991-04-29 1993-05-04 Century Manufacturing Co. Plasma arc ignition system
US5247152A (en) * 1991-02-25 1993-09-21 Blankenship George D Plasma torch with improved cooling
US5628924A (en) * 1993-02-24 1997-05-13 Komatsu, Ltd. Plasma arc torch
US6066827A (en) * 1997-09-10 2000-05-23 The Esab Group, Inc. Electrode with emissive element having conductive portions
US6191381B1 (en) 1999-04-14 2001-02-20 The Esab Group, Inc. Tapered electrode for plasma arc cutting torches
US8656577B2 (en) 2011-02-28 2014-02-25 Thermal Dynamics Corporation Method of manufacturing a high current electrode for a plasma arc torch

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU568475A1 (en) * 1975-03-10 1977-08-15 Osintsev Vladislav G Method of joining zirconium core to casing
CN112481538A (en) * 2019-09-12 2021-03-12 新奥科技发展有限公司 Cathode material and preparation method thereof, plasma torch cathode and preparation method thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2629836A (en) * 1949-03-24 1953-02-24 Gen Precision Lab Inc Enclosed arc lamp
US2662196A (en) * 1948-11-04 1953-12-08 Western Union Telegraph Co Concentrated arc lamp
US3198932A (en) * 1962-03-30 1965-08-03 Union Carbide Corp Arc electrode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2662196A (en) * 1948-11-04 1953-12-08 Western Union Telegraph Co Concentrated arc lamp
US2629836A (en) * 1949-03-24 1953-02-24 Gen Precision Lab Inc Enclosed arc lamp
US3198932A (en) * 1962-03-30 1965-08-03 Union Carbide Corp Arc electrode

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Materials and Techniques for Electron Tubes, by Walter H. Kohl, section entitled Hafnium on pages 532 534, Reinhold Publishing Corp. New York, N.Y., 1962. *

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3743955A (en) * 1971-07-13 1973-07-03 Us Air Force Radiation hardening read preamplifier
US3976853A (en) * 1973-06-20 1976-08-24 Siemens Aktiengesellschaft Non-fusible electrode, in particular for tungsten inert gas welding and a process for the production thereof
US4027134A (en) * 1973-11-12 1977-05-31 Tokyo Shibaura Electric Co., Ltd. Electrode for electrical discharge machining
US3930139A (en) * 1974-05-28 1975-12-30 David Grigorievich Bykhovsky Nonconsumable electrode for oxygen arc working
US4304984A (en) * 1978-05-11 1981-12-08 Bolotnikov Arkady L Non-consumable electrode for plasma-arc welding
US4229873A (en) * 1978-09-15 1980-10-28 Bykhovskij David G Method of producing nonconsumable electrode for use in arc techniques
DE2932930A1 (en) * 1979-08-14 1981-03-26 Gosudarstvennyj proektnyj i naučno-issledovatel'skij institut nikelevo-kobaltovoj i olovjannoj promyšlennosti, St. Petersburg Rapid inspection of non-consumable rod electrodes - by brief use in plasma torch using plasma gas contg. carbon cpds., followed by visual examination of electrode
US4581516A (en) * 1983-07-20 1986-04-08 Thermal Dynamics Corporation Plasma torch with a common gas source for the plasma and for the secondary gas flows
DE3618600A1 (en) * 1985-06-05 1986-12-11 AGA AB, Lidingö ELECTRODE FOR PLASMA SHEET PROCESSING
US4766349A (en) * 1985-06-05 1988-08-23 Aga Aktiebolag Arc electrode
EP0390998A1 (en) * 1989-04-03 1990-10-10 ESAB Welding Products, Inc. Method and apparatus for low voltage plasma arc cutting
US5023425A (en) * 1990-01-17 1991-06-11 Esab Welding Products, Inc. Electrode for plasma arc torch and method of fabricating same
US5097111A (en) * 1990-01-17 1992-03-17 Esab Welding Products, Inc. Electrode for plasma arc torch and method of fabricating same
EP0465109A2 (en) * 1990-06-26 1992-01-08 Daihen Corporation Electrode for use in plasma arc working torch
EP0465109A3 (en) * 1990-06-26 1992-04-15 Daihen Corporation Electrode for use in plasma arc working torch
US5200594A (en) * 1990-06-26 1993-04-06 Daihen Corporation Electrode for use in plasma arc working torch
US5247152A (en) * 1991-02-25 1993-09-21 Blankenship George D Plasma torch with improved cooling
US5208441A (en) * 1991-04-29 1993-05-04 Century Manufacturing Co. Plasma arc ignition system
US5628924A (en) * 1993-02-24 1997-05-13 Komatsu, Ltd. Plasma arc torch
US6066827A (en) * 1997-09-10 2000-05-23 The Esab Group, Inc. Electrode with emissive element having conductive portions
US6191381B1 (en) 1999-04-14 2001-02-20 The Esab Group, Inc. Tapered electrode for plasma arc cutting torches
US8656577B2 (en) 2011-02-28 2014-02-25 Thermal Dynamics Corporation Method of manufacturing a high current electrode for a plasma arc torch
US8680426B2 (en) 2011-02-28 2014-03-25 Thermal Dynamics Corporation High current electrode for a plasma arc torch

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GB1220205A (en) 1971-01-20
DE1907253A1 (en) 1971-05-06
SE343497B (en) 1972-03-13
FR2001963A1 (en) 1969-10-03

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