US3495019A - Induction furnace for melting aluminum and similar metals - Google Patents

Induction furnace for melting aluminum and similar metals Download PDF

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Publication number
US3495019A
US3495019A US736441A US3495019DA US3495019A US 3495019 A US3495019 A US 3495019A US 736441 A US736441 A US 736441A US 3495019D A US3495019D A US 3495019DA US 3495019 A US3495019 A US 3495019A
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United States
Prior art keywords
coil
crucible
furnace
melting
air
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US736441A
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English (en)
Inventor
John D Santi
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Briggs and Stratton Corp
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Briggs and Stratton Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • 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
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/16—Furnaces having endless cores
    • H05B6/20—Furnaces having endless cores having melting channel only
    • 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
    • Y10S65/00—Glass manufacturing
    • Y10S65/04—Electric heat

Definitions

  • an induction furnace of the type to which this invention relates comprises a crucible of refractory cementitious material with a substantially deep base and with upright walls that cooperate with the base to define a melting chamber.
  • a coil that is wound on a rectangular core and is adapted to be energized with alternating current.
  • a generally U-shaped molten metal passage in the base has upright legs which open to the melting chamber and which are located at opposite sides of the coil, and has its bight portion beneath the coil and extending transversely to it.
  • a more specific object of the invention is to provide a method and means for excluding air from the pores of the cementitious refractory material of the crucible of a melting furnace of the character described, to thereby prevent oxidization of metal in the molten metal passage of the crucible.
  • FIGURE 1 is a vertical sectional view of an induction furnace for melting aluminum and the like that embodies the principles of this invention
  • FIGURE 2 is a horizontal sectional view taken on the plane of the line 2-2 in FIGURE 1;
  • FIGURE 3 is a diagrammatic top view of a melting furnace incorporating a modified embodiment of the invention.
  • FIGURE 4 is a more or less diagrammatic vertical sectional view of an induction melting furnace embodying another version of the invention.
  • the numeral 4 designates generally an induction furnace comprising a crucible 5 of refractory cementitious material having substantially upright side walls 6 and a substantially deep base 7 which cooperate in defining a melting chamber 8.
  • a laminated core 10 which is rectangular as viewed from above and which has windings 9 on a pair of its opposite legs that comprise a coil connectable with a source of alternating current (not shown).
  • the base 7 there is also a generally U-shaped molten metal passage 11.
  • the upright legs 12 of the passage 11 open at their tops to the melting chamber 8, and its bight portion 13 is beneath the coil and extends transversely to its windings, intermediate their ends.
  • the upright passage portions 12 are spaced to opposite sides of the core 10, and in this case there is, as in many such furnaces, a third upright passage 14 which communicates the melting chamber 8 with the transverse passage portion 13 and which is substantially coaxial with the core.
  • the crucible Since the crucible is made of cementitious material, it is substantially porous. Heretofore air has been permitted to permeate the pores of the refractory material, and of course the hot metal in the crucible was readily oxidized by such air. Such oxidization occurred at all of the interfaces between the molten metal and the crucible, but it was most prevalentand most destructivein the molten metal passage 11. Actually, the prior practice of air cooling the coil materially contributed to the rapidity of oxidization of metal in the molten metal passage because cooling air was literally being forced through the pores of the cementitious refractory material, more or less directly to the neighborhood of the molten metal passage.
  • air is excluded from the pores of the refractory material by forcing inert gas under pressure into surface portions of the crucible that are remote from those of its surfaces which are normally in contact with molten metal, to thereby cause such inert gas to permeate the refractory material to the exclusion of air.
  • One means for thus forcing inert gas into the pores of the crucible material comprises a jacket 16 of steel or the like which surrounds at least the lower portion of the crucible, and which has its interior communicated, as by means of a duct 17, with a source 18 of an inert gas under above-atmospheric pressure.
  • the jacket 16 and the exterior crucible surface surrounded thereby thus cooperate to define a plenum chamber 24 from which the inert gas escapes through the pores of the refractory material.
  • the inert gas drives air out of its pores and then continues to prevent air from permeating the refractory.
  • Nitrogen is a very suitable inert gas for the purpose because it is readily available in pressurized containers, does not react with aluminum and similar metals and is completely harmless as it escapes into the air.
  • the pressure in the plenum chamber 24 can be permitted to vary rather widely so long as it is maintained high enough so that some of the inert gas is always permeating the refractory material and is not permitted to gos so high as to cause bubbling of the molten metal in the crucible.
  • cooling air excluded from the base portion of the furnace, other means must be provided for cooling the coil 9, or it must be of such nature as to be capable of withstanding substantial heat.
  • the conductor 19 of which the coil is wound is tubular so that water or other liquid coolant can be circulated through it. Its end portions extend out of the base of the furnace, as at 20, and are connected with hoses 21 or the like that lead to suitable means (not shown) for cooling the liquid and circulating it through the coil. Also connected to the projecting end portions of the coil are conductors 22 by which the coil can be connected with a current source.
  • the tubular conductor comprising the coil has a suitable insulation coating on its exterior.
  • the generally rectangular core 10 can be of conventional construction, comprising generally C-shaped laminations that can be inserted axially into the windings from opposite ends thereof.
  • a coolant jacket 23 Surrounding the coil is a coolant jacket 23 through which cooling liquid is also circulated.
  • the outer wall of this coolant jacket serves as a core mold that defines the coil receiving channel in the base of the crucible when the cementitious refractory is cast, and the liquid cooling of this jacket prevents heating of the windings by radiation from the interior of the crucible.
  • the cooling jacket has an inlet 25 and an outlet 26 that extend to the exterior of the furnace. Through suitable Ts and insulating ducts or hoses the coolant jacket inlet and outlet can be connected in a parallel cooling liquid flow circuit with the coil.
  • a jacket 16 of steel or the like again surrounds at least the lower portion of the crucible 5' to define a plenum chamber which is kept filled with a pressurized inert gas that permeates the refractory material and excludes air from its pores.
  • the laminated rectangular core 10' has two substantially elongated legs that have their medial portions more or less embedded in the base portion of the crucible and their end portions projecting outside the jacket 16. The other two legs 2.19 of the core are thus external to the jacket 16, and the windings 9 of the coil are on those external core legs. Hence the windings can be readily cooled by means of fans 27 or the like blowing across them.
  • the inner portions of the legs 110' of the core 10 in the FIGURE 3 embodiment of the invention will be subjected to substantial heating by conduction and radiation from the interior of the crucible, and will attain a temperature above the Curie temperature of most magnetic materials, the Curie temperature, of course, being that at which the material loses its ferro-magnetic properties. Hence it will 'be recognized that a material will have to be selected for the core 10' that has a very high Curie temperature.
  • the crucible 5 per se and the core 10 and windings 9" in its base are like those that have heretofore been conventional in induction melting furnaces in which the coil is intended for forced air cooling.
  • the jacket 16' of steel or the like which surrounds at least the lower portion of the crucible is somewhat larger than in the previously'described embodiments of the invention, so that it can accommodate in its interior a coolant radiator or heat exchanger 29 and a fan or blower 30.
  • the plenum 24 conjointly defined by the crucible and the jacket 16' isv kept filled with an inert gas, such as nitrogen, at a pressure somewhat above atmospheric.
  • the fan or blower 30 circulates such inert gas across the core 10 and windings 9 and through the radiator 29.
  • a suitable coolant liquid e.g., cold water
  • the core and coil are directly cooled by the circulating inert gas in the jacket and are indirectly cooled by the liquid circulating through the radiator 29, to which the inert gas gives up its heat.
  • the crucible could be surrounded by a jacket filled with inert gas, as in the embodiments hereinabove described, and the core and coil could be disposed in the base of the crucible, with no provision for their cooling.
  • the core material would have to have a very high Curie temperature and the coil would have to be capable of withstanding substantially high heat, comprising, for example, a conductor with ceramic insulation.
  • An induction furnace for melting aluminum and similar metals comprising a crucible of refractory material, and a coil which is in the body of the crucible and which is adapted to be energized with alternating current for inducing a current in metal in the crucible to effect heating of such metal, said induction furnace being characterized by:
  • (A) means defining a jacket around the exterior of the crucible, spaced from the outer surface of the crucible and cooperating therewith to define a plenum chamber;
  • (B) means for maintaining pressurized inert gas in said plenum chamber to cause such gas to permeate the refractory material of the vessel and thereby exclude air from the pores thereof.
  • An induction furnace for melting aluminum and the like comprising a coil adapted to be energized with alternating current and a crucible of cementitious material having a substantially deep base in which the coil is located, said crucible also having a melting chamber above the base and a molten metal passage in the base that has opposite end portions which open upwardly to the melting chamber so that metal in the melting chamber and said passage defines a closed loop in which a current can be induced in consequence of energization of the coil, to effect heating of the metal, said furnace being characterized by:
  • (A) means defining a jacket embracing a substantial portion of the exterior surface of the crucible and cooperating therewith to define a plenum chamber;
  • (B) means for maintaining inert gas in said plenum chamber at above atomspheric pressure to cause such gas to permeate the refractory material and thereby exclude air from its pores.
  • An induction furnace for melting aluminum and similar metals comprising a body of refractory material that defines a melting chamber and a passage that has opposite ends opening to the melting chamber, and a coil in the body of refractory material disposed to have flux linking relationship with metal in the melting chamber and said passage, for inducing a current in such metal by which the metal is heated, said furnace being characterized by:
  • (B) means for circulating cooling liquid into and out of the jacket for abstracting heat given off by the coil.
  • said means for preventing air from permeating the pores of the refractory material, to thereby prevent oxidization of metal being melted in the interior of the cruible, said means compising:
  • (B) means for maintaining inert gas in said plenum chamber at above-atmospheric pressure, so that such gas is caused to permeate the pores of the refractory material and thereby exclude air therefrom.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Furnace Details (AREA)
US736441A 1968-06-12 1968-06-12 Induction furnace for melting aluminum and similar metals Expired - Lifetime US3495019A (en)

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US73644168A 1968-06-12 1968-06-12

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3828107A (en) * 1970-05-19 1974-08-06 Daido Steel Co Ltd Plasma smelting furnace
US4141373A (en) * 1977-09-28 1979-02-27 Rjr Archer, Inc. Method for deoiling metal scrap
US5336291A (en) * 1992-07-02 1994-08-09 Toyota Jidosha Kabushiki Kaisha Method of production of a metallic composite material incorporating metal carbide particles dispersed therein

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1680595A (en) * 1925-10-26 1928-08-14 Nat Aniline & Chem Co Inc Current induction
US2503621A (en) * 1948-09-30 1950-04-11 Thompson Prod Inc Induction furnace
CH341949A (de) * 1955-09-19 1959-10-31 Patentverwertung Ag Verfahren und Vorrichtung zur Herstellung von Gussstücken
US3039864A (en) * 1958-11-21 1962-06-19 Aluminum Co Of America Treatment of molten light metals
US3092682A (en) * 1960-03-24 1963-06-04 Ajax Magnethermic Corp Submerged resistor type induction furnaces and methods and processes therefor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1680595A (en) * 1925-10-26 1928-08-14 Nat Aniline & Chem Co Inc Current induction
US2503621A (en) * 1948-09-30 1950-04-11 Thompson Prod Inc Induction furnace
CH341949A (de) * 1955-09-19 1959-10-31 Patentverwertung Ag Verfahren und Vorrichtung zur Herstellung von Gussstücken
US3039864A (en) * 1958-11-21 1962-06-19 Aluminum Co Of America Treatment of molten light metals
US3092682A (en) * 1960-03-24 1963-06-04 Ajax Magnethermic Corp Submerged resistor type induction furnaces and methods and processes therefor

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3828107A (en) * 1970-05-19 1974-08-06 Daido Steel Co Ltd Plasma smelting furnace
JPS5036407B1 (US07364359-20080429-C00003.png) * 1970-05-19 1975-11-25
US4141373A (en) * 1977-09-28 1979-02-27 Rjr Archer, Inc. Method for deoiling metal scrap
US5336291A (en) * 1992-07-02 1994-08-09 Toyota Jidosha Kabushiki Kaisha Method of production of a metallic composite material incorporating metal carbide particles dispersed therein

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BE726538A (US07364359-20080429-C00003.png) 1969-06-16

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