EP1711973A1 - Method for the production of graphite electrodes - Google Patents
Method for the production of graphite electrodesInfo
- Publication number
- EP1711973A1 EP1711973A1 EP04803711A EP04803711A EP1711973A1 EP 1711973 A1 EP1711973 A1 EP 1711973A1 EP 04803711 A EP04803711 A EP 04803711A EP 04803711 A EP04803711 A EP 04803711A EP 1711973 A1 EP1711973 A1 EP 1711973A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode body
- graphitization
- electrode
- impregnation
- connecting element
- 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- Withdrawn
Links
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
- H05B7/14—Arrangements or methods for connecting successive electrode sections
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Definitions
- the present invention relates to a method for producing a graphite electrode consisting of an electrode body and at least one connecting element arranged on one of the two end faces of the electrode body, in which the electrode body and the at least one connecting element are separated from one another by a method comprising the steps of forming a carbon-containing mass , Firing, impregnation and graphitization are produced before the electrode body and the at least one connecting element are connected to one another, and the graphite electrodes, electrode body and connecting elements obtainable with such a method.
- Graphite electrodes are used, for example, in electric arc furnaces for steel production.
- a voltage is applied to the graphite electrode, an arc is formed which leads from the lower end of the electrode to the melting material and which melts the melting material, for example steel scrap or sponge iron.
- the lower end of the electrode burns slowly and the electrode is consumed.
- electrode strands are usually used, which are pushed into the arc furnace to the extent that the lower end of the electrode burns off during furnace operation.
- Such an electrode string usually consists of individual, interconnected cylindrical electrodes or electrode bodies, which over
- the individual electrode bodies have for receiving the connecting elements truncated cone-like depressions with an internal thread on their two end faces, while the connecting elements have the shape of a double cone, that is to say two truncated cones joined together with their base surface, on the outer surfaces of which an external thread is arranged.
- the electrode strands are pushed in the direction of the melt by appropriate movement of a support arm which is connected to the upper end of the electrode strand.
- a new electrode body is screwed onto the upper end of the electrode string via a connecting element and the support arm is shifted upwards accordingly.
- the electrode strands When operating the arc furnaces, the electrode strands are subjected to high mechanical loads. Particularly in the case of strong inhomogeneities in the steel melt, for example due to scrap parts floating on it, strong bending forces occur at the upper end of the electrode strand in the vicinity of the support arm, which lead to a breakage of the connecting elements on their equator or the electrode body on their recesses arranged on the end face can. The broken electrode strand then falls into the melt, which results in considerable production downtimes. A break in the upper part of the electrode strand in particular has particularly serious consequences, since in this case the entire strand falls into the melt and has to be recovered in a considerable amount of time.
- US Pat. No. 6,058,133 discloses a cylindrical graphite electrode body which has a slot running helically along the electrode body. This slot is intended to prevent cracks from spreading by breaking through the slot as a result of the high temperature as it spreads, thereby preventing further spreading.
- the crack phenomena on electrodes are very diverse, so that in general it cannot be predicted in which direction and at what depth cracks will form.
- the slots on the electrode that were originally introduced to contain the cracks can themselves be the starting points for cracks or prevent the spreading of cracks at all or only insignificantly.
- An impregnation cycle generally comprises the impregnation of the shaped bodies with pitch under vacuum, followed by afterburning at about 800 ° C. (cf. Ullmann's Encyclopedia for Industrial Chemistry 2002, Vol. 6, page 313).
- the mechanical strength can only be increased slightly as the number of impregnation cycles increases.
- this slight improvement is offset by the relatively high costs of a further impregnation step.
- the cost-benefit ratio also deteriorates with every further impregnation cycle.
- the penetration of the shaped body through the Impregnant severely restricted. There are undesirable inhomogeneities across the cross section of the resulting strand elements.
- the invention is therefore based on the object of cost-effectively and effectively improving the strength of graphite electrodes.
- this object is essentially achieved in a method of the type mentioned at the outset in that the electrode body and / or the at least one connecting element are at least one more time impregnated and re-fired after the graphitization.
- electrode strands with a mechanical strength sufficient for use in electric arc furnaces were not can only be obtained by additional impregnation of the electrode body and connecting elements, but also if only either the electrode body or the connecting element of the graphite electrode is subjected to an impregnation step after the graphitization.
- the electrode bodies or connecting elements are burned in a manner known per se, preferably at temperatures between 700 and 1,300 ° C., particularly preferably at about 800 ° C., for about 500 hours in an oven under an inert gas or reducing atmosphere before the Electrodes are subjected to an impregnation step one or more times and then graphitized at temperatures of more than 2,500 ° C., particularly preferably more than 2,750 ° C. and very particularly preferably at about 3,000 ° C.
- the impregnation of the electrode body and / or the connecting element to be carried out after the graphitization can be carried out in any manner known to the person skilled in the art, in particular with the customary impregnation agents.
- the same impregnating agent, particularly preferably impregnating pitch is preferably used both in the at least one impregnation step to be carried out before the graphitization and in the at least one impregnation step after the graphitization.
- the objects to be treated are incubated with the impregnating agent for a time known to the person skilled in the art for this purpose.
- the electrode body and / or the at least one connecting element incubated with the impregnating agent for 2 to 10 hours, particularly preferably 4 to 6 hours.
- afterburning takes place between 600 and 1000 ° C., preferably between 700 and 900 ° C. and very particularly preferably between 750 and 850 ° C.
- the afterburning is preferably carried out for 60 to 180 hours, particularly preferably 75 to 100 hours.
- the method according to the invention is not limited with regard to the number of impregnation steps to be carried out before or after the graphitization. Particularly good results are obtained, however, if an electrode body is impregnated once before the graphitization and after the graphitization. For connection elements, however, a double impregnation before the graphitization followed by an impregnation after the graphitization is preferred. It goes without saying that the mechanical strengths, in particular bending strengths, both of the electrode body and of the connecting elements can be increased further if they are each subjected to two impregnation cycles after the graphitization.
- Electrode strands with the best possible mechanical properties are obtained if both the individual electrode bodies and the connecting elements are subjected to an impregnation after the graphitization.
- electrode strands with sufficient mechanical strength in particular sufficient bending strength at the upper end, can also be obtained if only the individual electrode bodies or the individual connecting elements are subjected to an impregnation after the graphitization.
- the graphite electrodes, electrode bodies and connecting elements obtainable with the method according to the invention are distinguished by improved mechanical properties, in particular higher mechanical strengths against bending forces, compared to those produced by a method according to the prior art.
- the mechanical strength can be increased by up to 20%.
- Electrode bodies with a diameter of 500, 600, 700 or 800 mm or connecting elements, for example with a diameter of 325 mm, obtainable with the method according to the invention by a single impregnation step after the graphitization typically have the following properties:
- graphite electrodes consisting of an electrode body and at least one connecting element, which can be obtained with the method according to the invention. These graphite electrodes are distinguished from the electrodes known from the prior art by their higher mechanical strength, in particular by their higher flexural strength.
- the present invention relates to an electrode body, which for the purposes of the present invention are also graphite electrodes, obtainable by a method comprising the steps of forming a carbon-containing mass, firing, single or multiple impregnation and graphitization, in which the electrode body has at least one after the graphitization is impregnated and re-fired again.
- the present invention relates to a connecting element obtainable by a method comprising the steps of forming a carbon-containing mass, firing, single or multiple impregnation and graphitization, in which the connecting element is impregnated and after-fired at least one more time after the graphitization.
- Both the electrode bodies according to the invention and the connecting elements according to the invention are distinguished by a higher mechanical strength compared to those known from the prior art, in particular with respect to bending forces, and are therefore ideally suited for producing electrode strands to be used in arc furnaces.
- Needle coke is preferably used as the starting material for the electrode bodies and the connecting elements as starting materials as a pyrolysis product in a mixture with coal tar pitch, the maximum particle size of the pyrolysis products for electrode bodies preferably being less than 35 mm, particularly preferably less than 30 mm and very particularly preferably a maximum of 25 mm and for connecting elements is preferably less than 10 mm, particularly preferably less than 5 mm and very particularly preferably a maximum of 3 mm.
- the carbon-containing mass is preferably shaped by extrusion, although other methods known to the person skilled in the art for this purpose, such as isostatic molding or vibration molding, can also be used.
- a molding compound was produced from 100 parts of needle coke with a maximum particle size of 25 mm and 25 parts of coal tar pitch.
- the mass was mixed for 0.5 hours in a kneading mixer at 160 ° C, then extruded at 120 ° C into a cylindrical strand and then fired in a conventional furnace at 800 ° C for 500 hours.
- the fired cylindrical carbon bodies were then impregnated once with an impregnation pitch for 5 hours and post-fired at 800 ° C. for 80 hours.
- the conventionally impregnated and afterburned carbon bodies were graphitized at about 3,000 ° C. in a manner known to the person skilled in the art.
- the graphite blanks thus obtained were again impregnated with impregnating pitch for 5 hours and after-baked at 800 ° C. for 80 hours.
- An electrode body was produced and measured by a method according to the prior art, namely analogously to Example 1 but without impregnation and afterburning after the graphitization.
- the inherent shadows of these electrode bodies are summarized in Table 1.
- a molding compound was produced from 100 parts of needle coke with a maximum particle size of 3 mm and 25 parts of coal tar pitch.
- the mass was mixed in a kneading mixer at 160 ° C for 0.5 hours, then extruded into a cylindrical strand at 120 ° C and then fired in a conventional furnace at 800 ° C for 500 hours.
- the fired cylindrical carbon bodies were then impregnated twice with an impregnation pitch for 5 hours and post-fired at 800 ° C. for 80 hours. it the conventionally impregnated and afterburned carbon bodies were then graphitized at about 3,000 ° C. in a manner known to the person skilled in the art.
- the graphite blanks thus obtained were again impregnated with impregnating pitch for 5 hours and after-baked at 800 ° C. for 80 hours.
- a connecting element blank was produced and measured using a method according to the prior art, namely analogously to example 2, but without impregnation and afterburning after the graphitization and with a total of three impregnation steps carried out before the graphitization.
- the properties of these electrode bodies are summarized in Table 1.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Ceramic Products (AREA)
- Discharge Heating (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0351115A FR2864417A1 (en) | 2003-12-18 | 2003-12-18 | Manufacture of graphite electrodes with improved strength due to tar impregnation after graphitisation, notably electrodes for electric arc steelmaking furnaces |
PCT/EP2004/014061 WO2005060027A1 (en) | 2003-12-18 | 2004-12-10 | Method for the production of graphite electrodes |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1711973A1 true EP1711973A1 (en) | 2006-10-18 |
Family
ID=34630588
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04803711A Withdrawn EP1711973A1 (en) | 2003-12-18 | 2004-12-10 | Method for the production of graphite electrodes |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1711973A1 (en) |
FR (1) | FR2864417A1 (en) |
MY (1) | MY146459A (en) |
WO (1) | WO2005060027A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113999011A (en) * | 2021-12-14 | 2022-02-01 | 中钢集团南京新材料研究院有限公司 | Short-process graphite preparation method |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
LU34949A1 (en) * | 1956-02-23 | |||
US4536359A (en) * | 1983-10-11 | 1985-08-20 | Nikku Industry Co., Ltd. | Method of manufacturing carbon electrode |
JP4290291B2 (en) * | 1999-09-30 | 2009-07-01 | コバレントマテリアル株式会社 | Carbon electrode for melting quartz glass |
US6500022B2 (en) * | 2001-03-30 | 2002-12-31 | Ucar Carbon Company Inc. | Threaded pin for carbon electrodes |
-
2003
- 2003-12-18 FR FR0351115A patent/FR2864417A1/en not_active Withdrawn
-
2004
- 2004-12-10 WO PCT/EP2004/014061 patent/WO2005060027A1/en not_active Application Discontinuation
- 2004-12-10 EP EP04803711A patent/EP1711973A1/en not_active Withdrawn
- 2004-12-17 MY MYPI20045228A patent/MY146459A/en unknown
Non-Patent Citations (1)
Title |
---|
See references of WO2005060027A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2005060027A1 (en) | 2005-06-30 |
FR2864417A1 (en) | 2005-06-24 |
MY146459A (en) | 2012-08-15 |
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Legal Events
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DAX | Request for extension of the european patent (deleted) | ||
17Q | First examination report despatched |
Effective date: 20071116 |
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RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: SGL CARBON SE |
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RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: SGL CARBON SE |
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Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
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Effective date: 20141117 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 20150328 |