US2744945A - Graphite furnace electrode for a stabilized arc - Google Patents

Graphite furnace electrode for a stabilized arc Download PDF

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Publication number
US2744945A
US2744945A US493637A US49363755A US2744945A US 2744945 A US2744945 A US 2744945A US 493637 A US493637 A US 493637A US 49363755 A US49363755 A US 49363755A US 2744945 A US2744945 A US 2744945A
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US
United States
Prior art keywords
electrode
arc
graphite
hole
furnace
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
US493637A
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English (en)
Inventor
Harry V Johnson
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.)
Union Carbide Corp
Original Assignee
Union Carbide and Carbon Corp
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 Union Carbide and Carbon Corp filed Critical Union Carbide and Carbon Corp
Priority to US493637A priority Critical patent/US2744945A/en
Priority to FR1142296D priority patent/FR1142296A/fr
Priority to CH333349D priority patent/CH333349A/fr
Priority to GB7386/56A priority patent/GB816907A/en
Application granted granted Critical
Publication of US2744945A publication Critical patent/US2744945A/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H05B7/14—Arrangements or methods for connecting successive electrode sections
    • 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
    • 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
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T403/00—Joints and connections
    • Y10T403/55—Member ends joined by inserted section
    • Y10T403/556—Section threaded to member

Definitions

  • This invention relates to a graphite electrode for an arc furnace and has for an object to provide more .eflicient utilization of energy by an electrode that makes possible a greater average power input, is adapted to have a more steady arc, and one which will prolong the life of furnace refractories.
  • the usual connecting nipple presents further dilficulty because it has been regarded as the structurally weaker element in the modern furnace electrode.
  • This nipple extends for approximately 10% to 15% of the total electrode length so that if an arc is to be stabilizedfor the entire electrode length the nipple must also be capa-
  • One section- 10 of a graphite electrode for an arc furnace is provided with a longitudinal hole 11.
  • Adjacent the lower end of the usual socket for a connecting nipple is an imperforate integral diaphragm 12 formed by taking care not to drill all the way through the entire electrode length.
  • This diaphragm needs to be only thin enough to prevent convection currents of air from rising through the electrode and out its upper end causing too rapid an oxidation of the graphite. Its minimum thickness may be as small as one eighth or a quarter of an inch because when such diaphragm approaches the lower end of the electrode it must be capable of being eroded through before the arc reaches the nipple in order that the arc may be continually stabilized.
  • the hole 11 gradually becomes larger as the are supporting end is approached. While the cross sectional shape of the lower end of the electrode is not always the same, that illustrated is perhaps typical. Adjacent the arc, investigation has shown the hole 13 to be enlarged due possibly to oxidation and other causes under the intense heat. Motion picture studies have shown the are not to wander as it did before over the lower outer side walls of the electrode and elsewhere. 1
  • the lower inner surface 14 near the bottom of the electrode is where the arc strikes and moves around these inner wall surfaces.
  • Arc stability is due to inability of inner wall surfaces to radiate heat away as rapidly as do the outer wall surfaces with the result that these inner surfaces 14 become hotter and therefore better adapted for electron emission than any other electrode surface in spite of the superior thermal conductivity and positive coefiicient of electrical resistance of graphite as compared with amorphous carbon.
  • the size of the hole 11 when drilled depends upon the electrode length in practice. For an electrode 96 inches long a drill no smaller than A to 1 inch in diameter will be found desirable on account of inevitable fiexure in a smaller size drill functioning as a cantilever beam.
  • the upper limit on drill size is largely economic and due to the high cost of a quantity of graphite being removed as well as the increase in electrical resistance of the electrode having a large hole. Common sizes of graphite electrodes cost several hundred dollars to produce. A factor affecting price is not only quantity of graphite but general bulk due to the long covered heating and cooling periods that such electrodes have to have in their manufacture. For such reason no consumer wants to pay for uneconomic bulk nor for graphite that cannot be consurned and utilized. Possibly a hole 3 inches in diameter may be an upper economic limit for the larger sizes of electrodes, as large as 40 inches in diameter and about 110 inches long.
  • the nipple 15 is of the usual graphite type and has a longitudinal hole 16 drilled nearly but not quite all the way through the entire length.
  • a diaphragm 1'7 is located preferably at the upper end of the nipple. With the diaphragm visible the usual workman will arrange the nipple to have the diaphragm 17 at the upper end. However no serious inconvenience will be encountered if the diaphragms 12 and 17 are placed next to each other.
  • each electrode in operation will include two sections connected by a nipple and in such event the controlling consideration is that somewhere there should always be a diaphragm to preclude any updraft and rapid oxidation of the bore.
  • the upper electrode section 18 will be of the same construction as the lower one.
  • Radial reservoirs 19 for pitch are preferably provided as described in the copendiug application of Johnson et al. Serial No. 461,714, filed October 12, 1954, for Pitch Cartridge for Electrode Joint, now Patent No. 2,735,705. A half inch hole 16 has been found satisfactory for many nipples.
  • an arc stabilizing hole in an electrode has resulted in about 10% more graphite being consumed in a given time during operation of a steel furnace having a 2 to 4 inch hole in a 14 inch diameter electrode than did a solid graphite electrode of the same size, but effected about a 15% more heat and electrical energy input.
  • This same hollow electrode required approximately minutes to melt down a charge of scrap as compared with minutes for a solid graphite electrode to melt down the same amount of scrap in the same furnace.
  • An oscillograph showed approximately .93 as the ratio of actual to theoretical power input for this hollow electrode as compared with about .84 as the same ratio for the same mentioned solid electrode.
  • the electrode with the 2 inch hole consumed about 7.5 inches of its length in the shorter time required for a charge of the same size in the same furnace, the electrode having the 3 inch hole consumed about 8 inches of its length per charge and the electrode with the 4 inch hole about 8.5 inches per charge.
  • the present electrode may be designated as hollow, it will be understood that it is only the lower portion of an electrode section or nipple that needs to be con tinually and such hollow portion is believed to be effective only when the diameter of'the hole has been enlarged at about the portion 13 and below and the temperature of the walls of the hole raised to a heat that will be more conducive to an electron discharge than will the outer walls of the electrode.
  • a non-circular shape to a hole causes an inefiicient use of graphite because of erosion and oxidation in the lower part of the electrode. Only a hole which is initially substantially circular can efficiently stabilize an are from a graphite electrode.
  • the slots 12a in Fig. 3 of Chappell prevent the hole 13a from being ever circular functionally.
  • This Chappell patent 6 has the slots 12 and 12a 2% to 4% of the cross sectional area of that electrode and the hole 13 of a diameter which is 10% to of the electrode diameter.
  • the invention claimed herein distinguishes both functionally as well as numerically and structurally from this non-equivalent Chappell suggestion.
  • each of the sections and nipple being provided with a longitudinal hole of a size which is at least large enough to stabilize an arc and reduce the likelihood of its being formed on an outer lower side surface of an electrode section, and a graphite diaphragm in at least one of a nipple and electrode section, said diaphragm being of a thickness such that erosion will penetrate the diaphragm by at least the time it reaches the lower end of the electrode from which an arc is formed.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Discharge Heating (AREA)
US493637A 1955-03-11 1955-03-11 Graphite furnace electrode for a stabilized arc Expired - Lifetime US2744945A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US493637A US2744945A (en) 1955-03-11 1955-03-11 Graphite furnace electrode for a stabilized arc
FR1142296D FR1142296A (fr) 1955-03-11 1956-03-05 électrode en graphite pour four à arc électrique
CH333349D CH333349A (fr) 1955-03-11 1956-03-07 Electrode en graphite pour four à arc électrique
GB7386/56A GB816907A (en) 1955-03-11 1956-03-09 Graphite furnace electrode for a stabilised arc

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US493637A US2744945A (en) 1955-03-11 1955-03-11 Graphite furnace electrode for a stabilized arc

Publications (1)

Publication Number Publication Date
US2744945A true US2744945A (en) 1956-05-08

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US493637A Expired - Lifetime US2744945A (en) 1955-03-11 1955-03-11 Graphite furnace electrode for a stabilized arc

Country Status (4)

Country Link
US (1) US2744945A (fr)
CH (1) CH333349A (fr)
FR (1) FR1142296A (fr)
GB (1) GB816907A (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2941828A (en) * 1957-09-27 1960-06-21 Speer Carbon Company Electrode connecting nipple and joint
US2969251A (en) * 1960-02-15 1961-01-24 Great Lakes Carbon Corp Carbon electrode joint
US3088762A (en) * 1960-01-27 1963-05-07 Siemens Planiawerke Ag Screw nipple joint for carbon electrodes
US3251926A (en) * 1964-09-02 1966-05-17 Union Carbide Corp Electrode joint for joining negative carbon electrodes
US3279912A (en) * 1962-10-02 1966-10-18 Union Carbide Corp Treating molten metals with multiple electric arc columns
US3715440A (en) * 1968-10-01 1973-02-06 Foseco Int Electric arc stabilization in electric arc melting using carbon electrodes
US3780259A (en) * 1971-10-06 1973-12-18 Trw Inc Nonconsumable tungsten electrode for arc welding
US3787336A (en) * 1970-04-21 1974-01-22 Foseco Int Electrodes for arc furnaces

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1137150B (de) * 1960-09-16 1962-09-27 Siemens Planiawerke Ag Formkoerper aus Kohle oder Graphit als Elektrode oder Verbindungsnippel

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1007151A (en) * 1910-05-17 1911-10-31 Internat Acheson Graphite Company Electrode.
US1091559A (en) * 1911-07-28 1914-03-31 Nat Carbon Co Electrode.
US1115027A (en) * 1911-08-02 1914-10-27 Nat Carbon Co Electrode.
US1640735A (en) * 1923-05-16 1927-08-30 Norske Elektrokemisk Ind As Process of making channeled continuous electrodes
US1912560A (en) * 1930-06-02 1933-06-06 Buffalo Electric Furnace Corp Refractory lined hollow electrode
US2603669A (en) * 1948-10-26 1952-07-15 Union Carbide & Carbon Corp Large electrode with thermal stress relief

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1007151A (en) * 1910-05-17 1911-10-31 Internat Acheson Graphite Company Electrode.
US1091559A (en) * 1911-07-28 1914-03-31 Nat Carbon Co Electrode.
US1115027A (en) * 1911-08-02 1914-10-27 Nat Carbon Co Electrode.
US1640735A (en) * 1923-05-16 1927-08-30 Norske Elektrokemisk Ind As Process of making channeled continuous electrodes
US1912560A (en) * 1930-06-02 1933-06-06 Buffalo Electric Furnace Corp Refractory lined hollow electrode
US2603669A (en) * 1948-10-26 1952-07-15 Union Carbide & Carbon Corp Large electrode with thermal stress relief

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2941828A (en) * 1957-09-27 1960-06-21 Speer Carbon Company Electrode connecting nipple and joint
US3088762A (en) * 1960-01-27 1963-05-07 Siemens Planiawerke Ag Screw nipple joint for carbon electrodes
US2969251A (en) * 1960-02-15 1961-01-24 Great Lakes Carbon Corp Carbon electrode joint
US3279912A (en) * 1962-10-02 1966-10-18 Union Carbide Corp Treating molten metals with multiple electric arc columns
US3251926A (en) * 1964-09-02 1966-05-17 Union Carbide Corp Electrode joint for joining negative carbon electrodes
US3715440A (en) * 1968-10-01 1973-02-06 Foseco Int Electric arc stabilization in electric arc melting using carbon electrodes
US3787336A (en) * 1970-04-21 1974-01-22 Foseco Int Electrodes for arc furnaces
US3780259A (en) * 1971-10-06 1973-12-18 Trw Inc Nonconsumable tungsten electrode for arc welding

Also Published As

Publication number Publication date
FR1142296A (fr) 1957-09-16
CH333349A (fr) 1958-10-15
GB816907A (en) 1959-07-22

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