US2805879A - Electrode joints - Google Patents

Electrode joints Download PDF

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Publication number
US2805879A
US2805879A US448323A US44832354A US2805879A US 2805879 A US2805879 A US 2805879A US 448323 A US448323 A US 448323A US 44832354 A US44832354 A US 44832354A US 2805879 A US2805879 A US 2805879A
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US
United States
Prior art keywords
nipple
kerfs
socket
electrode
electrodes
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
US448323A
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English (en)
Inventor
Edward C Thomas
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.)
GREAT LAKES CARBON Corp
Daewoo Engineering and Construction Co Ltd
Original Assignee
Daewoo Engineering and Construction Co Ltd
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
Priority to BE558765D priority Critical patent/BE558765A/xx
Application filed by Daewoo Engineering and Construction Co Ltd filed Critical Daewoo Engineering and Construction Co Ltd
Priority to US448323A priority patent/US2805879A/en
Application granted granted Critical
Publication of US2805879A publication Critical patent/US2805879A/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
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S403/00—Joints and connections
    • Y10S403/05—Carbon electrode

Definitions

  • This invention relates to an improved joint for carbon electrodes. More particularly, this invention relates to an improved nipple for joining carbon and graphite electrodes used in electrothermal furnaces.
  • carbon electrodes which may be either amorphous or graphitic in nature, in electrothermal processes is well established.
  • electrodes consisting of amorphous carbon are widely used in the manufacture of calicum carbide as well as in the manufacture of ferroalloys and other alloys in which the carbon content is not critical.
  • Graphite electrodes find particular utility in the manufacture of special alloy steels.
  • the product to be manufactured is subjected to a high temperature in an electrothermal or metallurgical furnace, the heat in said furnaces being supplied by passing an electric current of high amperage through an air space between the two or more carbon electrodes or between the electrodes and the charge.
  • the resultant high-temperature arc produces the melting, smelting or other electrothermal action desired.
  • Graphite electrodes for use in electric furnaces are commonly joined to form a continuous column as they are consumed, by a threaded, graphite, double male member, known in the art as a nipple and similar in function to that of a dowel pin.
  • the nipple of necessity, has a reduced cross section compared with the column of electrodes it supports. Accordingly, there is a stress concentration within the body of a nipple joining two electrodes, which demands that the mechanical strength of the nipple stock be greater than that of the material within the body of the electrodes it joins. As a consequence of this, nipple stock must be made of cokes known to produce stock of higher mechanical strength and density.
  • Socket splits result from the differential radial thermal expansion characteristics in the electrode joint, i. e. between the nipple and the socket. For example, in allowing a heated electrodejoint assembly to cool between electrothermal operations, the socket walls which had become stressed in tension in the hot furnace by the aforementioned excessive diametrical expansion of the nipple start to shrink due to radiant cooling of the outer surface of the joint.
  • Electrode spalling As a result of this shrinkage which is aded to the tensile stress generated when the joint became heated in the furnace, tremendous hoop stresses are set up within the socket which often cause the socket wall to crack. These hoop stresses are much greater, and have an entirely different origin than the cooling stresses which result in the condition referred to as electrode spalling. Spalling in electrodes is not restricted to the region of the joint but rather is a surface phenomenon throughout the length of the electrode. ttempts have been made to reduce this by cutting internal and external radial, longitudinal slots into the electrodes. The function of the internal slots is to dissipate contractile forces in the outer surface of the electrode by permitting movement of the side walls of each slot toward each other.
  • Figure 1 is a perspective view of a nipple it), having three kerfs 12 intersecting the threads 11.
  • Figure 2 is a cross-sectional view of the nipple shown in Figure 1 taken along the line 2-4.
  • Figure 3 is a similar cross-sectional view of a further embodiment of the invention wherein four kerfs are used.
  • Figure 4 is a cross-sectional view of a further embodiment of the invention wherein curved kerfs 13 are used.
  • Figure 5 is a cross-sectional view of a further embodiment of the invention having a single kerf 1'4 of Archimedean form.
  • a broad embodiment of the invention comprises preparing. a nipple bymixingtogether carbon aggregateof sn'chicarbon's or carbon producing materials as calcined petroleum coke, anthracite, graphite, electrode carbon scra orthefike' with a suflicienta'mount of pitch or'bitnnnnous materialto serve as a binder.
  • The'mixing. operation is usually conducted abovethe melting point of the binder in order to insure uniform distribution of the binder throughou't'th'e carbon aggregate.
  • Small amounts o'f viscou's petroleum oils may'be added as a lubricant, especially in the event that the nipple stock is to be prepared by extrusion througha' die. The extruded or' molded.
  • greennip'ple stock is baked inorder to carb'onize' the binder after which the bakedcarbon body may be: impregnated with a suitable impregnant after which it may be heated to'higher temperatures in order to graphitize the carbon, the carbonized impregnant and the-carbonized binder which comprises the nipple stock.
  • the nipple stock may then be machined into a threaded nipple having either; a'cylin'drical form or the tapered form illustrated in Figure 1.
  • At least three non-radial slots-or kerfs are cut into the nipple in the longitudinal direction with respect to the nipple axis. The depth of the slots is more than 40% of the major diameter of the nipple but in any case substantially short of severing a portion of the nipple.
  • a threaded graphite nipple is prepared as described above.
  • Three nonradial, longitudinal kerfs are then cut into the nipple in such a manner as to form a symmetrical linear pattern in any cross section, such as the pattern illustrated in Figure 2.
  • the depth of the kerfs is more than 40% of the major diameter of the nipple, but in any case is substantially short of severing any portion of the nipple.
  • the threaded nipple prepared as described above has four nonradial, longitudinal slots or kerfs cut into the nipple so as to form a symmetrical linear pattern in any transverse cross section of the nipple, each of the kerfs being in a plane perpendicular to the planes of the two adjacent kerfs.
  • This embodiment is illustrated in Figure 3.
  • At least three curvilinear kerfs arecut into a threaded nipple prepared as described above, so as to form curvilinear patterns in a transverse cross section of the nipple, the kerfs being of a depth more than 40% of the major diameter of the nipple but in-any case substantially short of severing a portion of the nipple.
  • This embodiment is illustrated in Figure 4.
  • acurvilinear nonradia l, longitudinal kerf or slot is cut into the nippleprepared as described above so as to form an Archimedean spiral in a transverse cross section of the nipple.
  • Such kerfs will naturally have a depth more than 40% of the major diameter of the nipple and in any case will not sever a portion of the nipple.
  • a spiral kerf such as this one, illustrated in Figure 5, has been found to be equivalent to the three or more kerfs described in the embodiments above.
  • Modification-s of the above embodiments include variations in which the cross-sectional pattern formed is nonsymmetrical and/or combinations of linear (straight lines) and curvilinear patterns.
  • width of the kerfs may'vary from about 0.035 inch to 0.125 inch;
  • a cardboard shim or equivalent within the kerfs;
  • Such shims will end greater rigidity to' the nipple-for purposes' ofassembly.
  • Subsequent use of the nipple in an electrode joint during electrothe'rmal operations will result in shrink age -andcarbonizationof-the shim, so that there will be little remaining to prevent movement of the sidewalls of the kerfs toward each other to achieve their assigned flilfiiii'rf of'stis'rlief.
  • F illifi'g' the kerrswith' a carbons ceous binder material (which is essentially a solid at room temperature) prior to assembly will serve the same purpose as the cardboard shims.
  • Example I A threaded graphite nipple (approximately 11" diameter) similar to that illustrated in Figure 1, but not slotted, was used to join two graphite electrodes (20" diameter) having appropriately threaded sockets. The assembly was lowered into a Globar furnace and heated to a temperature of 1390" C. The assembly was then removed from the furnace and allowed to cool suspended in the open air. One electrode socket split after 3 /2 minutes of cooling.
  • Example II A-nipple-such as that described in Example I was'sawed so as to provide a single longitudinal radial kerf of a depth of 60% of the-major diameter and a width of 0.035 inch.- The' nipple was used to join two electrodes as described above and the assembly was similarly lowered'into the furnace'and heated to 1450 C. On removal to cool, as described in Example I, no splits developed. The assembled jointwas returned to the furnace and heated to 1505 C. and again removed to cool. After 4 minutes o'f cooling, a split developed in one socket;
  • Example III A nipple such as'th'at described in Example II but-having akerf width of 0.125 inch was tested as described above heating'to 1450" C. No socket split developed. On reheating to 1505" C. a split developed after'5 /z minutes of'cooling.
  • ExampleIV A nipple such as that described in Example I was sawed so as to provide three radial longitudinal kerfs having a depth /2 the major radius or about 2% inches anda kerf of 0.035- inch. When tested to 1480 C. as described above, a socket splitdeveloped after 5 /2 minutes of cooling.
  • Example V Anipple such as that described in Example I was sawed so as to provide three nonradial longitudinal kerfs of a depth -Va'the radius and having a kerf width of 0.035 inch. When-tested at 1480- C. as described above, no socket splitsneveleped. The assembly was then heated to -1520' C; On coolinga; socket split developedafter- 3 36P- minu't'es;
  • Example VI A nipple su'ch a's'that described in Example Twas-sawed so as" to' provide three nonradial longitudinal kerfs of a' depth 64% of the 'major diameter of the nipple and havingfa'kerf'width' of .035 inch.
  • Example VII A nipplesuch-as that described in Exampl'e Vl-ex'cept that the kerf width' was 0.052 inch, was used in' anelectrode'assembly which was heated to'1600" C. On" 0001 ing; nosock'et splits 'developed.
  • Example VIII A nipplesuch-asthat described in ExampleVI, except that the depth-ofthe kerf was 57% of the major diameter, was used in an-electrode assembly which was heated to-1550 C. Oncooling, no socket spli-ts developed Example 1X A nipple such as that described in Example VIII except that the kerf width was .052 inch, was used in an electrode assembly which was heated to 1550" C. On cooling, no socket splits developed.
  • electrode joints having nipples with at least three radial, longitudinal kerfs of a depth more than 40% of the major diameter of the nipple but in any case substantially short of severing a portion of the nipple, can be carried to considerably higher temperatures, such as those encountered in commercial electrothermal furnace operations, without danger of developing socket splits.
  • carbon as used herein and in the appended claims is intended to include both the so-called gasbaked or amorphous carbon and also graphite.
  • a carbon nipple for joining carbon electrodes having at least three nonradial, longitudinal kerfs extending the entire length of the nipple and of a depth more than 40% of the major diameter of said nipple but in any case substantially short of severing a portion of said nipple.
  • a nipple according to claim 1 having three kerfs, said kerfs forming a linear pattern in a transverse cross section of said nipple.
  • a nipple according to claim 1 having three kerfs, said kerfs forming a symmetrical linear pattern in a transverse cross section of said nipple.
  • a nipple according to claim 1 having four kerfs, said kerfs forming a linear pattern in a transverse cross section of said nipple.
  • a nipple according to claim 1 having four kerfs, said kerfs forming a symmetrical linear pattern in a transverse cross section of said nipple, each of said kerfs being in a plane perpendicular to the planes of the two adjacent kerfs.
  • a nipple according to claim 1 in which said kerfs form curvilinear patterns in a transverse cross section of said nipple.
  • a carbon nipple for joining carbon electrodes having a longitudinal kerf extending the entire length of the nipple and forming an Archimedean spiral in a transverse cross section of said nipple, said spiral having its terminus at the approximate center of said cross section.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Discharge Heating (AREA)
US448323A 1954-08-06 1954-08-06 Electrode joints Expired - Lifetime US2805879A (en)

Priority Applications (2)

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BE558765D BE558765A (en(2012)) 1954-08-06
US448323A US2805879A (en) 1954-08-06 1954-08-06 Electrode joints

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3140967A (en) * 1959-04-30 1964-07-14 Siemens Planiawerke Ag Method of producing a cemented carbon electrode joint
US3161580A (en) * 1961-01-13 1964-12-15 Great Lakes Carbon Corp Graphite joints of highly uniform electrical resistance
US4450061A (en) * 1982-12-20 1984-05-22 Aluminum Company Of America Metal stub and ceramic body electrode assembly

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1287678A (en) * 1918-03-05 1918-12-17 Burton P Hall Dowel-pin.
US2125018A (en) * 1932-11-08 1938-07-26 Hamill William Wilson Plug for insertion in walls and other places
US2482176A (en) * 1948-04-03 1949-09-20 Nat Carbon Co Inc Electrode connecting pin
US2527294A (en) * 1949-01-03 1950-10-24 Great Lakes Carbon Corp Carbon electrode

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1287678A (en) * 1918-03-05 1918-12-17 Burton P Hall Dowel-pin.
US2125018A (en) * 1932-11-08 1938-07-26 Hamill William Wilson Plug for insertion in walls and other places
US2482176A (en) * 1948-04-03 1949-09-20 Nat Carbon Co Inc Electrode connecting pin
US2527294A (en) * 1949-01-03 1950-10-24 Great Lakes Carbon Corp Carbon electrode

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3140967A (en) * 1959-04-30 1964-07-14 Siemens Planiawerke Ag Method of producing a cemented carbon electrode joint
US3161580A (en) * 1961-01-13 1964-12-15 Great Lakes Carbon Corp Graphite joints of highly uniform electrical resistance
US4450061A (en) * 1982-12-20 1984-05-22 Aluminum Company Of America Metal stub and ceramic body electrode assembly

Also Published As

Publication number Publication date
BE558765A (en(2012)) 1900-01-01

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