US3235373A - Process for production of ultra clean steel - Google Patents

Process for production of ultra clean steel Download PDF

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Publication number
US3235373A
US3235373A US153650A US15365061A US3235373A US 3235373 A US3235373 A US 3235373A US 153650 A US153650 A US 153650A US 15365061 A US15365061 A US 15365061A US 3235373 A US3235373 A US 3235373A
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electrode
carbon
melt
vacuum
furnace
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US153650A
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English (en)
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Sidney W Poole
Thomas E Perry
Roderick J Place
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Republic Steel Corp
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Republic Steel Corp
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Priority to US153650A priority Critical patent/US3235373A/en
Priority to GB32579/62A priority patent/GB1002106A/en
Priority to LU42271D priority patent/LU42271A1/xx
Priority to NL282866A priority patent/NL282866A/xx
Priority to BE623082A priority patent/BE623082A/xx
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/16—Remelting metals
    • C22B9/20—Arc remelting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B4/00—Electrothermal treatment of ores or metallurgical products for obtaining metals or alloys
    • 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
    • Y02P10/20—Recycling

Definitions

  • the steel product from the remelt is of much improved properties when the first melting has been made by the consumable electrode vacuum melting technique to give a first melt substantially free of oxygen and then to remelt this material by the consumable electrode vacuum melting method.
  • the first melting step be performed by the consumable electrode vacuum melting so as to remove various impurities, and by such method of performing the first melting step also to avoid the addition of other impurities such as refractory materials which result in inclusions or other disadvantages or undesired properties in the ultimate product.
  • this first melting is performed by other methods, such as used in the prior art, this detracts from the results that can be obtained by the consumable electrode vacuum remelting.
  • the process of this invention permits the use of carbon alone for removal of oxygen and that the amount of carbon for such purpose can be calcu lated and easily controlled so as to give no more than the desired carbon aim in the resultant products.
  • an ultra clean steel is produced from iron powder of high purity such as electrolytic iron, etc. by blending the iron powder of high purity with an appropriate amount of carbon, with or without alloying metals, forming or briquetting the resultant mixture into consumable electrodes, vacuum melting the resultant consumable electrode, forging the ingot from the resultant melt into another consumable electrode, and then repeating the vacuum melting step.
  • the vacuum melting steps of the consumable electrodes are conducted in copper crucibles and refractory contamination is thereby avoided.
  • the forging step can be omitted where a larger crucible is used in the second vacuum melting step which will accommodate a consumable electrode having the size of the first melt ingot.
  • the accompanying drawing illustrates a schematic arrangement of a typical consumable electrode vacuum furnace.
  • Iron powder of such sufiicient purity can be prepared in accordance with prior practice used in the hydrogen reduction of electrolytic iron. For example satisfactory removal of sulfur from electrolytic iron is effected with wet hydrogen at l500l700 F. for 2-4 hours.
  • the resultant product after grinding, is blended with finely divided carbon and, when desired, with specified amounts of alloying metals, such as nickel, chromium, molybdenum, vanadium, etc., and formed or briquetted into desired consumable electrode sections, for example, at about 50,000 pounds per square inch.
  • the electrode sections can be vacuum sintered at about 1750 F. or can be sintered in an inert gas, such as argon, at temperatures up to 2200 F.
  • briquettes of the same length, with each having a cross section one quarter of that of the ultimate electrodes and then to weld four quarters into one electrode.
  • High pressure hydrostatic pressing of electrodes with a cylindrical configuration can also be used utilizing pressure conditions which will give an equivalent amount of binding effect.
  • the atmosphere is exhausted preferably down to a pressure of 1-2 microns.
  • the electrode is taken to a temperature at which melting starts the pressure rises as high as 1000 microns (1 mm.) depending on the capacity of the pumping equipment to remove the gases given off.
  • the electrode is thus arc-melted into a copper crucible under a vacuum of less than about 1 mm. (1000 microns), advantageously with a leak rate in the furnace of less than one micron per minute.
  • the product from this melt is then forged into a new electrode shape and the resultant electrode remelted under a vacuum of no more than 100 microns (0.1 mm.) preferably no more than 10 microns (0.01 mm.) of mercury.
  • an ingot of 5 inch diameter from the first melt is forged into an ingot of 3 inch diameter for the second melt when a crucible of the same size is being used in the first and second melts.
  • the resultant ingot from the first vacuum melting has holes, particularly at the top of the ingot, resembling the holes in swiss cheese. These are removed in the forging operation. If desired, the forging step can be avoided by conditioning the top and bottom ends of such an ingot from a first vacuum melt to obtain a smooth surface, and thereafter welding together a series of such ingots in a linear arrangement and remelting into a crucible of suitable diameter.
  • An important feature of this invention is the manner in which the oxygen content is reduced in the first electrode melting.
  • the amount of carbon added to the iron powder is based on the amount required for reducing the oxygen plus the amount needed to give the desired carbon content in the ultimate product.
  • the carbon content of the first ingot may vary linearly through the ingot with the highest concentration being at the top, it is sometimes advantageous to invert the first melt ingot or ingots for the second melting in order to distribute the carbon uniformly throughout the final ingot.
  • the vacuum can be effected by a mechanical pump in the early stages for preliminary removal of the atmosphere and then by an oil diffusion pump to more completely exhaust gases and produce the desired vacuum.
  • the type of equipment and method of effecting vacuum arc melting can be of various types normally used for such purposes. Typical of a type of apparatus suitable for this purpose is that shown in Patents Nos. 2,727,936, issued December 20, 1955; and 2,818,461, issued December 31, 1957.
  • high purity fine powder is preferably used, such as electrolytic iron.
  • sulfur and oxygen content need to be reduced to the low value indicated above, a preliminary hydrogen treatment is given.
  • alloying metals which are also hydrogen reducible, such as nickel, molybdenum, cobalt, etc., such powders are also added and blended with the iron powder for this preliminary treatment.
  • the resultant powder is treated advantageously with wet hydrogen at temperatures of 1500 to 1800 F. for a period of from 2 to 4 hours which is generally sufficient to drop the sulfur to the desired low value.
  • the hydrogen used for this purpose is saturated with water vapor at approximately 150 F. After this treatment, the wet hydrogen is removed and the powdered metal treated with dry hydrogen at the same temperature for approximately 15 minutes to effect optimum oxide removal. The powder mixture is then cooled in dry hydrogen.
  • the foregoing treatment produces a loosely sintered cake which is then ground, such as by a standard single disc attrition mill of the usual type. While the particle size is not critical, a mesh size of approximately 40 is generally satisfactory.
  • the resultant product is then mixed with finely divided carbon such as graphite, and at the same time can be mixed with any non-hydrogen reducible metals, in powder form, such as chromium, nickel and molybdenum, which are desired in the ultimate steel product.
  • the amount of carbon added is calculated roughly on the basis of approximately -200% of the theoretical amount required to convert the oxygen present in the powder as oxides to carbon monoxide. The excess is to compensate for physical losses incurred during melting probably due to the fact that the gas emanating from the reaction mass sweeps out some of the finely divided carbon from the system.
  • the required amount should also include any amount desired to be present in the resultant steel, referred to as the carbon aim.
  • the amount of carbon added should also take into account the carbon that is already present in the iron powder. Therefore, the amount of carbon to be added to the iron powder can be calculated roughly as the carbon aim plus 1.352 times the stoichiometric amount required to reduce the oxygen present to carbon monoxide, minus the amount of carbon already present in the iron
  • the mixed powder is formed by compression into the electrode shapes or segments which will make up the final electrode.
  • pressures of 40,000 to 50,000 psi. are adequate to form such electrodes or electrode segments.
  • These electrodes or electrode segments are advantageously vacuum sintered for approximately 2 hours at about 1750 F.
  • This sintering operation effects a cohesion of the metal particles and also eliminates some amount of oxygen. While other methods, such as hydrostatic pressing, etc. can directly effect sufficient cohesion of the particles to give the electrodes the required strength for subsequent use, subsequent vacuum sintering has been found to be advantageous in many cases.
  • the segments can be welded together by means of inert gas welding. Various other methods of pressing and assembling electrodes can be used in the practice of this invention.
  • Consumable electrode 1 is held in position by supporting means (not shown) but positioned in a region above copper crucible 2.
  • the copper crucible is cooled by water flowing in water inlet 3 and out water outlet 3' and circulating between the copper crucible and the outer supporting shell 4.
  • This copper crucible acts as a receptacle for the melt 5.
  • Power supply 6 feeds current through conductor 7 and through power tube 8 to electrode 1, and through conductor 9 to the copper crucible.
  • the arcing effect between the melt in the crucible and the consumable electrode is shown by the jagged lines connecting the electrode 1 and the melt 5.
  • the position of the consumableelectrode isadjusted upward gradually to control the arcing as the level of 5 is raised by additional melt.
  • Vacuum pump 10 creates and maintains a vacuum on the furnace and exhaust gases are forced out through outlet 11.
  • the resultant ingot is formed into the desired electrode shape for the second vacuum melting step.
  • This ingot from the first melting step has a somewhat cellular character resembling the holes or openings in swiss cheese which is apparently caused by the gas escaping from the melt during this first melting.
  • the cellular structure is more predominant near the top of the ingot. Therefore, the forging operation serves the double function of condensing the ingot by removal of such holes and also converting the ingot to a desired diameter for subsequent use as a consumable electrode.
  • the ingot from the first consumable electrode vacuum melt is found to have a cellular character near the top of the ingot as described above
  • the ingot from the second melt is found to be sound and dense and free from this cellular character. This freedom from cellular structure is very likely due to the fact that there is no evolution of great quantities of carbon monoxide in the second melting as there is in the first melting.
  • EXAMPLE I A finely divided iron powder produced by electrolytic means and reduced by hydrogen as described above with a resultant analysis of 0.02% carbon, 0.05% oxygen, 0.006% sulfur and 0.005% phosphorus, was mixed with finely divided carbon, manganese, chromium and ferrosilicon powders to give a blend containing 1.12% by Weight of added carbon, 0.35% manganese, 1.50% chromium and 0.3% of a ferro-silicon alloy containing silicon. This blend was pressed under 50,000 pounds per square inch pressure to give rods having a cross-section 1.5 inches square and approximately 15 inches long. These rods were vacuum sintered at about l-500 microns at 1750 F.
  • the ingot from the first melt was forged at about 2100 F. to about a two inch diameter and then turned on a lathe to produce an electrode for a second melt 1.75 inch diameter and 13 inch length with a weight of pounds.
  • This electrode was melted in a consumable electrode vacuum melting electric arc furnace at an amperage of 1200 amperes for 7 minutes to give an ingot having a diameter of 3.5 inches, a length of 3.5 inches and a weight of 8.5 pounds.
  • An average analysis of samples taken from the ingot inch from the top and 1% inches from the bottom, had the following average analyses: 0.835% carbon, 0.225% Mn, 0.006% phosphorus, 0.006% sulfur, 0.235% silicon, 0.05% nickel, 1.45% chromium, and 0.0011% oxygen.
  • Finely divided electrolytic iron powder having 0.018% carbon, 0.005% phosphorus, 0.008% sulfur, and 0.08% oxygen was mixed with finely divided carbon, nickel, chromium and molybdenum powders to give a blend having 0.78% C, 2.0% Ni, 1.5% Cr, and 0.50% Mo.
  • This blend was shaped as in Example I into rods having a cross-section 1.5 inches square and a length of inches. These were vacuum sintered at 1750 F. at 1-500 microns for 2 hours. After vacuum sintering the carbon content was 0.635%.
  • An electrode was assembled from eight of these rods with an assembled cross-section 3 inches square and length of 30 inches.
  • the square cross-section was made by putting together the four cross-sections of 4 rods each having cross-sections 1.5 inches square.
  • the length of the rods were staggered so that the diagonally opposite rods had the same length.
  • the diagonally opposite sections were made by two full lengths of the original rods. The other two sections were made by cutting two rods to half lengths, using half lengths as the end portions for these other two diagonally opposite sections and using a full length as the middle section.
  • rods A and A are full length rods in diagonally opposite relationship to rod D and to another rod D which is not shown but which is in the same linear relationship to D as A is to A.
  • Half-sections B and B" are in diagonally opposite relationship to half-sections C and C" and likewise B and C are full length rods in diagonally opposite relationship to each other so as to give strength to the assembled electrode.
  • the rods were welded to each other in this relationship.
  • the welded electrode was melted in a consumable electrode vacuum melting electric furnace at an amperage of 10002800 for about minutes at a reduced pressure of 7 .5-600 microns of mercury.
  • the resultant ingot was 6.5 inches in diameter and 6.5 inches long and weighing 54 pounds.
  • Analyses of a sample taken from the bottom center and the top center of the ingot had the following average values: 0.591% C, 0.01% Mn, 0.005% P, 0.008% S, 0.01% Si, 1.99% Ni, 1.64% Cr, 0.50% Mo, and 0.00095% 0.
  • This ingot was forged at 2150 F. and turned on a lathe to a 3 inch diameter for use as a second melt electrode, inverting the electrode for the second melt.
  • the second melt was conducted in the same furnace as the first melt, using the amperage of 800-2600, with the reduced pressure at 6-8 microns and taking about 9 minutes for the complete melting.
  • the resultant ingot had a diameter of 5.5 inches, height of 4.75 inches and weighed 29 pounds.
  • Various test results from samples taken from this ingot are summarized in the following tables which give the inclusion rating, notched tensile strengths, ratio of notched to unnotched tensile strengths and Charpy V- notched impact tests.
  • the notched tensile strengths are given for various temperatures of double draw in thousands of pounds per sq. in. (K s.i.).
  • the Charpy V- notched impact tests are given in foot-pounds (ft. lbs.).
  • alloying metals such as aluminum and titanium are desirably not added as starting materials since they have a tendency to react with any oxygen present.
  • these can be added to the electrode used in the second melt by drilling a hole in the electrode and inserting plugs of the alloying metal.
  • silicon in substantial amounts as an alloying metal, it is generally preferred to add this to the second melt in the form of an alloy, for example by dropping the alloy into the hot melt.
  • the process of this invention is desirably applied to the production steels and ferrous alloys containing at least 50% iron therein, preferably at least 75% iron.
  • the size of the electrode and the size of ingot produced in any particular melt is governed merely by the manner of assembling the electrode and the size of the furnace used.
  • FIG. 3 illustrates an assembly of larger electrodes, in this case using 9 rods of square cross-section to make up the cross-section of the assembled electrode and using the equivalent of 3 lengths of the rods to make up the assembled length of the electrode.
  • the top layer at the left end is made up of rods E, F, and G.
  • the rows in which E and G appear are assembled of rods having the normal rod length.
  • F is a rod of halflength, as is the rod F in the same top row, whereas rods F and F" are of the normal rod length. In this way the rods are staggered so that the ends of the rods do not meet in the same cross-sectional area of the assembled electrode.
  • the series of rods J, J, I" and J have the same arrangement of lengths as described above for F, F, F and F.
  • series of rods in linear arrangement with H and L have similar arrangements.
  • the series of rods M, M and M", as well as the series of rods in the line having K as the end rod has a similar linear 10 arrangement as shown for G, G and G". In this way the various rods are staggered with adjacent rods and therefore have greater resistance to shearing in the ultimate welded assembly. Greater numbers of rods can be similarly assembled to make larger electrodes.
  • the consumable electrode can be assembled in various manners either by being pressed in a unitary assembly or by being pressed into a number of smaller pieces which are united in various manners in an electrode assembly.
  • a process for the preparation of an ultra clean steel comprising the steps of (a) blending finely divided carbon with a finely divided iron powder having no more than 0.01 percent by weight of sulfur and no more than 0.01 percent by weight of phosphorus therein, the amount of said carbon being such that the combined weight of carbon in the iron powder and of the added carbon powder is sufficient to supply the desired carbon content for the ultimate steel product and to react with the oxygen contained in said iron powder for conversion to carbon monoxide,
  • said iron powder is an iron produced by electrolytic refinement which has been treated with Wet hydrogen at approximately 15001800 F. and subsequently treated with dry hydrogen at approximately 1500-1800" F., said powder thereafter being pressed into said electrode shape under a pressure of at least 40,000 p.s.i. and subsequently vacuumsintered at a temperature of approximately 1750 F. for at least 1.5 hours.
  • said iron powder is an iron produced by electrolytic refinement and which has been treated with wet hydrogen at approximately 1500-1800 F. and subsequently treated with dry hydrogen at approximately 1500-1800 F., said powder thereafter being pressed under a pressure of at least 40,000 p.s.i. into a number of long, narrow shapes, smaller than the desired ultimate electrode size, said pressed shapes are sintered in an inert atmosphere, and said sintered shapes are assembled and joined into an electrode.
  • a process for the preparation of an ultra clean steel comprising the steps of (a) forming a finely divided iron powder, having no more than 0.01 percent by weight of sulfur and no more than 0.01 percent by Weight of phosphorus therein, into a shape and of sulficient cohesive character to be adapted for ultimate use as an electrode in a consumable electrode vacuum electric arc furnace, said shaped electrode having a carbon content therein sufiicient to supply the desired carbon content of the ultimate steel product and to convert the oxygen content of said electrode to carbon monoxide,

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Geochemistry & Mineralogy (AREA)
  • General Life Sciences & Earth Sciences (AREA)
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  • Environmental & Geological Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
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US153650A 1961-11-20 1961-11-20 Process for production of ultra clean steel Expired - Lifetime US3235373A (en)

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Application Number Priority Date Filing Date Title
US153650A US3235373A (en) 1961-11-20 1961-11-20 Process for production of ultra clean steel
GB32579/62A GB1002106A (en) 1961-11-20 1962-08-24 Process for production of ultra clean steel
LU42271D LU42271A1 (fr) 1961-11-20 1962-08-27
NL282866A NL282866A (fr) 1961-11-20 1962-09-05
BE623082A BE623082A (fr) 1961-11-20 1962-10-01

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GB (1) GB1002106A (fr)
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3341321A (en) * 1963-10-09 1967-09-12 Skf Ind Inc Process for treating primarily metallic materials
US3387967A (en) * 1965-02-08 1968-06-11 Republic Steel Corp High purity steels and production thereof
US3657026A (en) * 1969-07-28 1972-04-18 Westinghouse Electric Corp High initial permeability fe-48ni product and process for manufacturing same
US3732915A (en) * 1971-10-07 1973-05-15 A Lugovoi Vacuum arc furnace
US4589916A (en) * 1984-02-23 1986-05-20 Daido Tokushuko Kabushiki Kaisha Ultra clean stainless steel for extremely fine wire
US20060198419A1 (en) * 2005-03-04 2006-09-07 Allan Intermill Cemented electrode joint and process for curing the same
US20070039418A1 (en) * 2003-10-08 2007-02-22 Hitachi Metals, Ltd. Method for producing steel ingot

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4150978A (en) * 1978-04-24 1979-04-24 Latrobe Steel Company High performance bearing steels
DE2822657B2 (de) * 1978-05-24 1980-06-12 Vereinigte Edelstahlwerke Ag (Vew), Wien Verfahren zur Herstellung von Abschmelzelektroden großen Durchmessers

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1434395A (en) * 1920-01-30 1922-11-07 Metal & Thermit Corp Electric furnace
US1555313A (en) * 1920-03-06 1925-09-29 Rohn Wilhelm Process of melting and degasifying metals under reduced pressure
US2234127A (en) * 1936-12-24 1941-03-04 Mautsch Robert Process of manufacture of a metallurgical product intended to bemelted for forming ametal or an alloy
GB671171A (en) * 1950-05-02 1952-04-30 Metro Cutanit Ltd An improved process for forming ingots of refractory metal
US3072982A (en) * 1953-07-13 1963-01-15 Westinghouse Electric Corp Method of producing sound and homogeneous ingots

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1434395A (en) * 1920-01-30 1922-11-07 Metal & Thermit Corp Electric furnace
US1555313A (en) * 1920-03-06 1925-09-29 Rohn Wilhelm Process of melting and degasifying metals under reduced pressure
US2234127A (en) * 1936-12-24 1941-03-04 Mautsch Robert Process of manufacture of a metallurgical product intended to bemelted for forming ametal or an alloy
GB671171A (en) * 1950-05-02 1952-04-30 Metro Cutanit Ltd An improved process for forming ingots of refractory metal
US3072982A (en) * 1953-07-13 1963-01-15 Westinghouse Electric Corp Method of producing sound and homogeneous ingots

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3341321A (en) * 1963-10-09 1967-09-12 Skf Ind Inc Process for treating primarily metallic materials
US3387967A (en) * 1965-02-08 1968-06-11 Republic Steel Corp High purity steels and production thereof
US3657026A (en) * 1969-07-28 1972-04-18 Westinghouse Electric Corp High initial permeability fe-48ni product and process for manufacturing same
US3732915A (en) * 1971-10-07 1973-05-15 A Lugovoi Vacuum arc furnace
US4589916A (en) * 1984-02-23 1986-05-20 Daido Tokushuko Kabushiki Kaisha Ultra clean stainless steel for extremely fine wire
US20070039418A1 (en) * 2003-10-08 2007-02-22 Hitachi Metals, Ltd. Method for producing steel ingot
US7597737B2 (en) * 2003-10-08 2009-10-06 Hitachi Metals, Ltd. Method for producing steel ingot
US20060198419A1 (en) * 2005-03-04 2006-09-07 Allan Intermill Cemented electrode joint and process for curing the same
WO2006096323A1 (fr) * 2005-03-04 2006-09-14 Ucar Carbon Company Inc. Joint d’électrode cimenté et procédé de vulcanisation dudit joint

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GB1002106A (en) 1965-08-25
LU42271A1 (fr) 1963-02-27
BE623082A (fr) 1963-04-01
NL282866A (fr) 1965-01-11

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