EP0142476A2 - Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen - Google Patents

Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen Download PDF

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Publication number
EP0142476A2
EP0142476A2 EP84830293A EP84830293A EP0142476A2 EP 0142476 A2 EP0142476 A2 EP 0142476A2 EP 84830293 A EP84830293 A EP 84830293A EP 84830293 A EP84830293 A EP 84830293A EP 0142476 A2 EP0142476 A2 EP 0142476A2
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EP
European Patent Office
Prior art keywords
electrode
composite
electrodes
arc furnaces
materials
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Withdrawn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
EP84830293A
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English (en)
French (fr)
Other versions
EP0142476A3 (de
Inventor
Italo Letizia
Mario Cavigli
Paolo D'ambosio
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.)
Elettrocarbonium SpA
Original Assignee
Elettrocarbonium SpA
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 Elettrocarbonium SpA filed Critical Elettrocarbonium SpA
Publication of EP0142476A2 publication Critical patent/EP0142476A2/de
Publication of EP0142476A3 publication Critical patent/EP0142476A3/de
Withdrawn legal-status Critical Current

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    • 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

Definitions

  • This invention refers to prebaked carbon electrodes used in arc furnaces and, more particularly, in submerged arc furnaces for electrometallurgic processes.
  • the elements supplying the current to the reaction area consist of electrode columns made from a carbon material.
  • Electrodes columns consist of individual components, the electrodes, generally of a cylindrical shape, and connected to each other at their ends by suitable joints which ensure the mechanical and electrical continuity of the columns.
  • the type of electrode known in the art and traditionally used at present consists of either, a solid cylindrical body, or an axially bored body made from a carbon material of substantially uniform characteristics throughout the body.
  • the bottom of the electrode column is submerged to a certain extent into the charge of the furnace, while at a higher level the column carries current supplying metallic blocks called "contact clamps", provided with forced water cooling. Accordingly, the current-flows through the column lenght comprised between these "contact clamps" and the lower end of the column.
  • the temperature within the electrode is not constant and significant temperature differences are not in the different areas due to the heat developed by the Joule effect within the electrodes through which the current flows and due to the transfer of this heat from the electrode to the outside.
  • thermo-mechanical stresses in the electrodes These stresses are variously distributed in the electrode and act on the material also in the absence or external forces.
  • thermo-mechanical stresses are mainly related to the following factors:
  • Factors "a” - “e” determine the temperature values in the electrodes, while factors “f” and “g” determine the value of the internal stresses due to the temperature distribution.
  • the stress values are related to the above mentioned parameters, it may happen that in particular operating conditions the highest values of these internal stresses axceed locally the mechanical strength of the material, thus causing the formation of cracks which prevent the electrode column from normally operating.
  • the efficiency level of the electrodes is very important, this efficiency level being the electrode capacity to supply high intensity current and withstand the chemical attacks and mechanical and thermo-mechanical stresses to which the electrode is subjected during its use in the electric furnace operation, both in steady and in transient conditions.
  • the mechanical strength of the material can be equally improved by acting on the raw materials and the production technologies to reduce the risk of cracks, the internal stresses having the same values.
  • the electrodes used at present for electrometallurgical purposes still comprise almost exclusively either conventional solid cylindrical bodies or cylindrical bodies having an axial bore of small size.
  • the increased resistance of the electrodes to the cracks caused by internal mechanical stresses is obtained by using "composite” electrodes.
  • These electrodes consist of two coaxial cylinders joined to each other (Fig. 1): an outer cylinder from a material A (hereinafter called the “rind”) and an inner cylinder from a different material B (hereinafter called the "core").
  • the use of two different materials having suitable characteristics is intended to reduce the maximum values of the mechanical stresses which are the direct cause of the cracks. Furthermore, in the "composite" electrodes of this invention the use of two different materials is intended to reduce the maximum stresses at the outer surface since, as it is known, these maximum stresses generally occur in the electrodes at this outer surface.
  • the applicant has determined, through accurate measurements, the values of the electric and thermal conductivity, the mechanical properties and the coefficients of thermal expansion at the operating temperatures on electrodes obtained from different raw materials and using different manufacturing technologies and thermal baking cycles. Moreover, the applicant has carried out studies of the most typicel transient thermal cycles which the electrodes are subject to during operation.
  • a suitable mathematical model has allowed an evaluation to be carried out of the distribution of the mechanical stresses in each section of the electrode column, both in the electrode's normal working conditions, that is in steady thermal conditions, and in particular conditions such as the periodical slipping of the electrode, a power blackout or a restarting of the operation, that is in transient thermal conditions.
  • the distribution of the mechanical stresses has been calculated at various current densities and for different electrode diameters also in the area of the joints of the electrode columns.
  • the reduction of the stresses on the electrode surface is obtained by making the "rind” from a material having a higher electrical and thermal conductivity in respect to material "B" used for the internal “core”; material “B” of the internal “core” should also have a lower coefficient of thermal expansion and a lower modulus of elasticity as compared with material "A" of the "rind” at the operating temperatures used in practice.
  • the ratio between the "rind” and the “core” radius should be suitably chosen.
  • the new composite electrode is different from a conventional electrode of the same size and subjected to the same operating conditions, because the maximum values of the mechanical stresses (expressed in N/mm 2 ) occurring therein are lower than the maximum values of the mechanical stresses occurring in a conventional electrode made from only one of the materials from which the composite electrode is made.
  • the first electrode is a "composite” electrode (rind “A” and core “B")
  • the second and third electrodes are conventional and made from materials "A” and "B", respectively.
  • the three electrodes being supplied with a total current of 68,000 Amperes.
  • Material "A” is an electrographite based material and has the following main characteristics at room temperature:
  • Material "B” is an anthracite based material and has the following main characteristics at room temperature:
  • the “composite” electrode consists of a "rind” made from material “A” having a tickness of 150 mm and a “core” made from material “B”, having a radius of 450 mm.
  • this composite electrode is manufactured by placing, on the shaping step, the green mixture of material "B” in the axial area of the cylinder and then filling completely the cylinder with the green mixture of material "A". The raw electrode cylinder is then subjected to a normal baking cycle.
  • the furnace is of the open or semiclosed type such as a furnace for the production of silicon metal.
  • the following table I shows the calculation results obtained for the temperature in the three above mentioned electrodes at the axis and the periphery thereof. These results refer to an electrode section which is placed between the lower edge of the contact clamps and the upper surface of the charge since this is the section where the highest thermal stresses generally occur in the electrodes and the brekages are more likely to take place. As is evident, the temperature difference between the axis and the periphery of the "composite" electrode has an intermediate value with respect to electrodes "A" and "B” but, however, it is quite close to the temperature difference of electrode "A".
  • the following table II shows the values resulting from the calculation of the highest axial tensile stresses occurring at the electrode periphery.
  • the composite electrode is 1,200 mm in diameter, with a "rind” of material “A” 150 mm thick, and a “core” of material “B” with a radius of 450 mm.
  • the total current is 68,000 Amperes.
  • the steady-state calculation gives the following characteristics:
  • the drawing clearly shows an axial sectional view of a composite electrode according to the invention.
  • the "composite” electrodes of the invention can be obtained by extrusion, vibration, molding or by any other suitable proces known in the art.
  • the "rind” “A” and the “core” “B” can consist of any carbonaceous material, with no restriction.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Discharge Heating (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Ceramic Products (AREA)
EP84830293A 1983-11-11 1984-10-31 Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen Withdrawn EP0142476A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT4932983 1983-11-11
IT49329/83A IT1171887B (it) 1983-11-11 1983-11-11 Elettrodo di carbone precotto a struttura composita per forni elettrici ad arco

Publications (2)

Publication Number Publication Date
EP0142476A2 true EP0142476A2 (de) 1985-05-22
EP0142476A3 EP0142476A3 (de) 1985-08-14

Family

ID=11270368

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84830293A Withdrawn EP0142476A3 (de) 1983-11-11 1984-10-31 Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen

Country Status (3)

Country Link
EP (1) EP0142476A3 (de)
IT (1) IT1171887B (de)
NO (1) NO844492L (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT401303B (de) * 1993-09-06 1996-08-26 Voest Alpine Ind Anlagen Verfahren zum herstellen einer bodenanode für ein metallurgisches gefäss
WO2000027168A1 (de) * 1998-11-04 2000-05-11 C. Conradty Nürnberg Gmbh Elektrode für elektrometallurgische verfahren
EP1406473A1 (de) * 2002-10-04 2004-04-07 Sgl Carbon Ag Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen
DE102009047320B3 (de) * 2009-11-30 2011-07-21 Sgl Carbon Se, 65203 Radial gradierte Elektrode mit Interface-Schicht
CN102196611A (zh) * 2010-03-19 2011-09-21 瓦克化学股份公司 石墨电极
US9131538B2 (en) 2009-12-16 2015-09-08 Italghisa S.P.A. Electrode paste for electrodes in a graphite and/or anthracite with hydrocarbon base

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH97969A (de) * 1921-06-10 1923-02-16 Deprez Th Verfahren zur Herstellung von Elektroden.
GB241461A (en) * 1925-04-15 1925-10-22 Carl Wilhelm Becker Improvements in or relating to furnace electrodes
US2300503A (en) * 1939-10-17 1942-11-03 Nat Carbon Co Inc Composite article
GB773579A (en) * 1952-08-13 1957-05-01 Lorraine Carbone Improvements in or relating to anodes for powerful electric arcs
DE1137150B (de) * 1960-09-16 1962-09-27 Siemens Planiawerke Ag Formkoerper aus Kohle oder Graphit als Elektrode oder Verbindungsnippel
FR2019521A6 (de) * 1968-10-01 1970-07-03 Foseco Trading Ag
DE3145993A1 (de) * 1981-11-20 1983-06-01 Sigri Elektrographit Gmbh, 8901 Meitingen Graphitelektrode fuer lichtbogenoefen

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH97969A (de) * 1921-06-10 1923-02-16 Deprez Th Verfahren zur Herstellung von Elektroden.
GB241461A (en) * 1925-04-15 1925-10-22 Carl Wilhelm Becker Improvements in or relating to furnace electrodes
US2300503A (en) * 1939-10-17 1942-11-03 Nat Carbon Co Inc Composite article
GB773579A (en) * 1952-08-13 1957-05-01 Lorraine Carbone Improvements in or relating to anodes for powerful electric arcs
DE1137150B (de) * 1960-09-16 1962-09-27 Siemens Planiawerke Ag Formkoerper aus Kohle oder Graphit als Elektrode oder Verbindungsnippel
FR2019521A6 (de) * 1968-10-01 1970-07-03 Foseco Trading Ag
DE3145993A1 (de) * 1981-11-20 1983-06-01 Sigri Elektrographit Gmbh, 8901 Meitingen Graphitelektrode fuer lichtbogenoefen

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT401303B (de) * 1993-09-06 1996-08-26 Voest Alpine Ind Anlagen Verfahren zum herstellen einer bodenanode für ein metallurgisches gefäss
WO2000027168A1 (de) * 1998-11-04 2000-05-11 C. Conradty Nürnberg Gmbh Elektrode für elektrometallurgische verfahren
DE19850735C1 (de) * 1998-11-04 2000-09-21 Conradty Nuernberg Gmbh C Elektrode für elektrometallurgische Verfahren
EP1406473A1 (de) * 2002-10-04 2004-04-07 Sgl Carbon Ag Vorgebackene Kohlenstoffkompositelektrode für elektrische Lichtbogenöfen
DE102009047320B3 (de) * 2009-11-30 2011-07-21 Sgl Carbon Se, 65203 Radial gradierte Elektrode mit Interface-Schicht
US9131538B2 (en) 2009-12-16 2015-09-08 Italghisa S.P.A. Electrode paste for electrodes in a graphite and/or anthracite with hydrocarbon base
CN102196611A (zh) * 2010-03-19 2011-09-21 瓦克化学股份公司 石墨电极
EP2368847A1 (de) * 2010-03-19 2011-09-28 Wacker Chemie AG Graphitelektrode
US8366892B2 (en) 2010-03-19 2013-02-05 Wacker Chemie Ag Graphite electrode
CN102196611B (zh) * 2010-03-19 2013-08-14 瓦克化学股份公司 石墨电极

Also Published As

Publication number Publication date
EP0142476A3 (de) 1985-08-14
NO844492L (no) 1985-05-13
IT1171887B (it) 1987-06-10
IT8349329A0 (it) 1983-11-11

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Inventor name: D'AMBOSIO, PAOLO

Inventor name: CAVIGLI, MARIO

Inventor name: LETIZIA, ITALO