EP0334007B1 - Procédé pour diminuer l'usure d'électrodes en graphite - Google Patents

Procédé pour diminuer l'usure d'électrodes en graphite Download PDF

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Publication number
EP0334007B1
EP0334007B1 EP89102063A EP89102063A EP0334007B1 EP 0334007 B1 EP0334007 B1 EP 0334007B1 EP 89102063 A EP89102063 A EP 89102063A EP 89102063 A EP89102063 A EP 89102063A EP 0334007 B1 EP0334007 B1 EP 0334007B1
Authority
EP
European Patent Office
Prior art keywords
electrode
electrodes
graphite
coating
contact jaws
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
EP89102063A
Other languages
German (de)
English (en)
Other versions
EP0334007A1 (fr
Inventor
Hubert Dipl.-Chem. Dr. Jäger
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.)
Sigri GmbH
Original Assignee
Sigri GmbH
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 Sigri GmbH filed Critical Sigri GmbH
Publication of EP0334007A1 publication Critical patent/EP0334007A1/fr
Application granted granted Critical
Publication of EP0334007B1 publication Critical patent/EP0334007B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/06—Electrodes
    • H05B7/08—Electrodes non-consumable
    • H05B7/085—Electrodes non-consumable mainly consisting of carbon
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/12—Arrangements for cooling, sealing or protecting electrodes

Definitions

  • the invention relates to a method for reducing the erosion of graphite electrodes when they are used in an electric arc furnace by coating the lateral surfaces located below the contact jaws by means of nozzle arrangements surrounding the electrodes with an oxidation-resistant protective layer.
  • the graphite electrodes used in electric arc furnaces are heated to temperatures by the thermal energy generated in the electric arc and the development of Joule heat within the electrodes, at which carbon with the oxygen increases to the surrounding air Carbon oxides react.
  • the reactions briefly referred to as erosion, are not limited to the outer surface of the cylindrical electrode, but extend below approximately 1000 ° C. almost over the entire volume of the electrode accessible through the pore system.
  • the erosion of the lateral surface causes a reduction in the electrode diameter, the erosion inside the electrode also largely disrupts the structure, as a result of which smaller structural elements are loosened and chipped.
  • Metallic protective layers have therefore been proposed for these electrodes which conduct the electrical current well, but whose temperature resistance is often not sufficient. Better thermal resistance is achieved by incorporating ceramic fillers into a metallic matrix (DE-PS 12 71 007) or also by using silicon as a coating material which is applied by plasma spraying in a vacuum (DE-OS 34 46 286).
  • Metallic protective layers have the disadvantage that they easily weld or fry with the cooled contact jaws made of copper and the contacts are damaged or destroyed. To avoid the damage, special graphite-containing layers have been proposed, which are applied to the contact jaws or the metallized outer surface of the electrode (DE-OS 30 28 348, DE-OS 32 15 831).
  • Electrode consumption could be reduced by up to 15% in some furnaces thanks to the cooling process; in other furnaces, the reduction in consumption was significantly lower, and in some cases the jacket burn-up even increased.
  • the reasons for the different results are probably instabilities of the water film and steam jacket, triggered for example by thermal convection currents, and the adsorption of water in the pore system of the graphite electrode. The adsorbed water reacts with the carbon at higher temperatures and the sponge-like soft zones typical of wet electrodes are created.
  • This process has essentially the same disadvantages as described above for direct cooling with water, such as the formation of spongy zones caused by in-pore oxidation of the water vapor.
  • Another disadvantage of this method is that the film-forming substances are not deposited uniformly on the surface of the electrode piece located between the electrode holder and the furnace cover, since the electrode strand is added in batches. Little or nothing is deposited in the well-cooled areas near the electrode holders, because there the evaporation is low and the washing-out effect of the cooling liquid is great, while in the very hot areas near the furnace cover, a lot because of the strong evaporation there crystallized out more.
  • the electrodes are operated below the furnace cover, there are insufficiently protected zones and zones which the coating can tear due to excessive layer thickness. The result is a zone-by-zone oxidative weakening of the electrode strand below the furnace cover. The effect of the coating produced in this way is low and also uneven.
  • the invention has for its object to produce an oxidation-resistant protective layer on the outer surface of graphite electrodes with simple technical means, which effectively protects the electrode against the attack of atmospheric oxygen under all loads in the electric arc furnace.
  • the object is achieved with a method of the type mentioned in the introduction that the outer surfaces of the graphite electrodes after each lowering and renewed locking of the electrodes in the contact jaws and after reaching an average jacket temperature of at least 400 ° C with a 15 to 20% aqueous solution of primary aluminum phosphate (Al (H2pO4) three times) is sprayed until a layer is formed which contains 300 to 500 g / m2.
  • Al primary aluminum phosphate
  • Graphite electrodes are placed in the solution at room temperature one or more salts are immersed or the solution is applied to the outer surface by brushing or spraying. The electrodes are then dried and heated to approximately 500 to 600 ° C., the heating rate being approximately 60 to 600 K / h. This forms a water-insoluble, oxidation-resistant film firmly anchored in the pores.
  • one or more nozzle rings are expediently attached to the electrode holder below the contact jaws and enclose the electrode string. After each of the above-described displacement of the electrode string in the axial direction, the free section of the electrode between the contact jaw and the furnace cover is sprayed with the coating solution, the duration of the coating depending on the growth of the protective layer.
  • the aqueous coating solution should contain about 15 to 25% monoaluminum phosphate, and 300 to 500 g / m2 of monoaluminum phosphate is expediently required to form a closed layer which protects the graphite electrode, which corresponds to about 1 to 3 l / m2 of coating solution.
  • the method enables the coating of graphite electrodes with simple means, such as are used for water cooling of the electrode jacket, and the production of layers which have a much better protective effect than the "water layers".
  • the application of the method is not limited to graphite electrodes, but also extends to carbon electrodes, which are mainly used in thermal reduction furnaces.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Discharge Heating (AREA)
  • Coating By Spraying Or Casting (AREA)

Claims (1)

1. Procédé pour diminuer l'usure d'électrodes en graphite se trouvant dans un four en fonctionnement par application d'un revêtement sur la surface enveloppe de cette électrode, revêtement se situant au-dessous des mâchoires de contact et au-dessus de la fermeture du four, au moyen de l'installation d'injecteurs autour des électrodes, à l'aide d'une couche protectrice stable à l'oxydation, caractérisé en ce que les surfaces enveloppes des électrodes de graphite sont arrosées avec une solution aqueuse contenant 15 à 20% d'orthophosphate primaire d'aluminium Al(H₂PO₄)₃, après chaque descente et nouveau serrage des électrodes dans les mâchoires de contact, et après que la température moyenne de la surface enveloppe ait atteint au moins 400°C, jusqu'à ce qu'il se soit formé une couche qui contienne 300 à 500 g/m2 de phosphate d'aluminium.
EP89102063A 1988-03-19 1989-02-07 Procédé pour diminuer l'usure d'électrodes en graphite Expired - Lifetime EP0334007B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3809361A DE3809361A1 (de) 1988-03-19 1988-03-19 Verfahren zur verringerung des abbrands von graphitelektroden
DE3809361 1988-03-19

Publications (2)

Publication Number Publication Date
EP0334007A1 EP0334007A1 (fr) 1989-09-27
EP0334007B1 true EP0334007B1 (fr) 1991-04-10

Family

ID=6350232

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89102063A Expired - Lifetime EP0334007B1 (fr) 1988-03-19 1989-02-07 Procédé pour diminuer l'usure d'électrodes en graphite

Country Status (2)

Country Link
EP (1) EP0334007B1 (fr)
DE (2) DE3809361A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2692748B1 (fr) * 1992-06-18 1998-07-17 Savoie Electrodes Refract Joint de raccordement d'electrodes de four electrique.
MX2020013150A (es) 2018-10-15 2021-02-18 Chemtreat Inc Electrodos para horno de enfriamiento por pulverizacion con un liquido de enfriamiento que contiene agentes tensioactivos.
EP3815465B1 (fr) 2018-10-15 2023-03-29 Chemtreat, Inc. Procédés de protection d'électrodes de four avec un liquide de refroidissement qui contient un additif

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB891273A (en) * 1960-05-30 1962-03-14 United Steel Companies Ltd Improvements relating to electric arc furnaces
DD205428A1 (de) * 1982-06-07 1983-12-28 Elektrokohle Lichtenberg Veb Verfahren zur herstellung schutzbeschichteter graphitelektroden
US4487804A (en) * 1982-08-02 1984-12-11 Nalco Chemical Company Coating to prevent the oxidation of electrodes during electric furnace steel making
JPS5951496A (ja) * 1982-09-18 1984-03-24 松下電器産業株式会社 カ−トリツジヒ−タの製造方法
US4726995A (en) * 1985-11-13 1988-02-23 Union Carbide Corporation Oxidation retarded graphite or carbon electrode and method for producing the electrode
JPH0795474B2 (ja) * 1987-03-17 1995-10-11 日本カ−ボン株式会社 電気ア−ク製鋼等金属の溶解および精錬法ならびにそれに供する電極冷却装置

Also Published As

Publication number Publication date
DE3809361A1 (de) 1989-09-28
DE58900079D1 (de) 1991-05-16
EP0334007A1 (fr) 1989-09-27

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