US3041434A - Method of and apparatus for inductively heating metal - Google Patents

Method of and apparatus for inductively heating metal Download PDF

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Publication number
US3041434A
US3041434A US840162A US84016259A US3041434A US 3041434 A US3041434 A US 3041434A US 840162 A US840162 A US 840162A US 84016259 A US84016259 A US 84016259A US 3041434 A US3041434 A US 3041434A
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United States
Prior art keywords
strip
work
coil
field
conductor
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Expired - Lifetime
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US840162A
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English (en)
Inventor
Alf Fritz
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Deutsche Edelstahlwerke AG
AEG AG
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Deutsche Edelstahlwerke AG
AEG AG
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Priority claimed from DED28994A external-priority patent/DE1084850B/de
Application filed by Deutsche Edelstahlwerke AG, AEG AG filed Critical Deutsche Edelstahlwerke AG
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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
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/36—Coil arrangements
    • H05B6/365—Coil arrangements using supplementary conductive or ferromagnetic pieces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/60—Continuous furnaces for strip or wire with induction heating
    • 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

  • inductively heating strip and sheet two basically different methods are employed.
  • the one consists in passing the strip or sheet through the effective range of an appropriately formed induction coil which embraces the work.
  • the magnetic field distribution emanating from the coil is such that the field acts on the work longitudinally.
  • the use of a longitudinal field has the ad'- vantage that the heating efiiciency is relatively high and, more particularly, that it permits magnetically conductive sheet to be heated. That this is possible is due to the absence of a component of force which draws the sheet into contact with the turns of the coil since the mechanical components of force cancel each other in every direction.
  • heating in a longitudinal field has the drawback that relatively high frequencies must be employed to heat the relatively thin sheet in an economical way. It has been found that when heating strip of a thickness of about 0.1 mm., frequencies below 10000 to 5000 c./s. must not be employed because the currents will effectively penetrate into the strip only when the frequencies exceed the stated frequency levels.
  • transverse field for inductively heating strip.
  • This method consists in drawing the strip between an appropriate inductor assembly in which the several inducing conductors extend transversely to the lengthwise direction of the strip on one or both of its sides. This arrangement causes a current to be induced inside the strip which flows in the plane of its surface. It is thus possible to apply much lower frequencies, such as the frequency of the power supplied through the mains.
  • the strip may be passed through a fiat coilshaped inductor fed with a medium frequency current of relatively low power density and comprising conductor sections facing the surfaces of the strip and extending at right angles to the strip edges, the conductors passing around the strip edge from one side of the strip to the other at an angle exceeding 25.
  • This arrangement permits of an economic heating cffect due to the reduction in the power density, but it likewise sets up a longitudinal magnetic field inside the strip so that depending upon the thickness of the strip relatively high frequencies must still be employed.
  • the present invention deals with the problem of overcoming the drawbacks of the above mentioned methods and of providing a method and an inductor which as such are designed for longitudinal heating but which are rendered operative to achieve a transverse field heating effect in the work.
  • the pres ent invention proposes to separate the magnetic fields emanating from the several conductors comprised in the coil by means of a material which will conduct the field so that it is directed on to the work in such a way that the current induced in the work will exclusively flow in the plane of the work.
  • the method proposed by the invention is thus adapted to combine the advantages of transverse field heating with the advantage gained by an inductor arrangement for longitudinal field heating.
  • the drawbacks inherent in either method are eliminated by the method according to the invention because even in the case of extremely thin sheet relatively low frequencies may be employed and a relatively high efficiency thereby achieved, whilst at the same time tendency of the work to be drawn into contact with the induction coil is avoided because the mechanical forces of attraction are compensated.
  • a preferred apparatus comprising an induction coil of fiat shape, the conductors on each side of the work (which is passed through the coil) being parallel to one another as well as parallel with the conductors on the opposite side, the connecting loops being situated in the vicinity of the edges of the work and the several conductors which form the induction coil being so arranged that the distance d between the individual conductors on each side of the coil is at least 25.
  • the distance d between the individual conductors on each side of the coil is at least 25.
  • a casting or mouldable resin incorporating iron powder for embedding the conductors of the induction coil.
  • a high proportion of iron powder is added to the resin and the compound cast or moulded around the conductors in such a way that the inside of the induction coil remains free.
  • a protective layer of a plastic incorporating substances of a nonferromagnetic electrically non-conducting and non-abrasive nature is provided.
  • quartz meal Such a layer is magnetically neutral but it forms an intimate mechanical bond with the outside field-conducting layer, especially if applied to the latter before it has set.
  • the protective layer mechanically protects the conductors of the induction coil and the incorporated quartz imparts a satisfactorily high temperature resistance thereto.
  • FIGS. 1a and lb illustrate the principle of the known method of induction heating in a longitudinal field.
  • FIGS. 2a and 2b show the general arrangement and the direction of flow of the current within the work with transverse field induction heating
  • FIG. 3a in longitudinal section illustrates the preferred apparatus for performing the method according to the invention
  • FIG. 3b shows the flow path of the current within the work.
  • FIG. la illustrates the known arrangement for heating in a longitudinal field.
  • the induction coil 1 embraces a strip 2 which passes in continuous motion through the coil.
  • the coil induces a current 3 in the strip in the manner shown in FIG. lb.
  • This figure shows the strip in cross-section. To permit this current to flow, the strip must therefore be sufficiently thick and the frequency sufficiently high.
  • FIG. 2a illustrates a known arrangement for heating by means of a transverse field.
  • the sheet metal strip 2 travels between inductors 4 and 4 surrounded by magnetic yokes 5 and 5 for conducting the magnetic flux.
  • the field emanating from these coils passes transversely through the strip and gives rise to a current 6 which flows in a path in the plane of the strip, as illustrated in FIG. 2b.
  • the apparatus according to the invention is shown in FIG. 3a in longitudinal section.
  • the strip 2 travels through the induction coil and the effective individual conductors 7, 7 of the coil are parallel to one another and to the strip faces.
  • the several conductors of the coil on either side are spaced at least (i525 apart.
  • the conductors on the one side are in staggered arrangement in relation to those on the other side. All the conductors are surrounded by a field-conducting material 8 in which they are embedded. However this material so surrounds them as to leave free an effective face of each conductor facing the work.
  • This field-conducting material which consists of a casting or mouldable resin with iron powder incorporated therein and which thus assumes a resultant permeability of about confines the magnetic field 9 and 9' emanating from each conductor to the conductor itself so that it individually takes efiect in the work 2, a magnetic field resulting from the combination of all the condoctors and passing through the work longitudinally being avoided.
  • each individual conductor 7 and 7' generates in the strip 2 a separate current 10 the path of which is shown in FiG. 3b and is located in the plane of the strip.
  • the formation of this current path is not now controlled by the thickness of the strip ⁇ ; but merely depends upon the mutual distance between the several conductors. If these conductors, as required, are spaced at least (1526 apart on one side of the strip then the arrangement will permit such a current path to de velop with a satisfactory degree of efficiency.
  • the inside surface of the induction coil is provided with an additional layer 11 of castable or mouldable resin which is cast on to the mass of the field-conducting material 8, said layer 11 preferably incorporating quartz meal.
  • the incorporation of quartz meal renders the layer more resistant to temperature and at the same time provides a surface of high mechanical strength inside the coil which protects it from damage.
  • This additional layer 11 is applied at a time when the resin compound 8 containing the iron powder is about to set. The two diiferently constituted cast res-in compounds 8 and 11 will thus be prevented from mixing and at the same time a homogeneous transition from the material 8 to layer 17. will be achieved, ensuring a bond of maximum strength therebetween.
  • a method of inductively heating relatively thin sheet, strip and the like work of large surface area which consists in relatively displacing the work and at least one surrounding flat induction coil which is partially embedded in a magnetic field-conducting material, in the direction of the axis of the coil, producing a plurality of separate magnetic fields each about a different conductor-section of the coil, said sections being parallel to one another and extending transversely of the direction of the said relative movement, the permeability of the material and the spacing of said sections being such as to ensure the effective separation of the said fields, and by a supply frequency not exceeding 10,000 cycles per second inducing in the work separate currents flowing in the plane of the work without creating a resultant longitudinal magnetic field by the combined effect of all the said conductor-sections.
  • An apparatus for inductively heating relatively thin sheet, strip and the like work comprising at least one flat induction coil adapted to receive the work and including conductor sections adapted to lie on each side of the work with those on either side parallel with one another and parallel with those on the opposite side and including joining sections adapted to lie in the region of the work edges, the said conductor sections being spaced so that the distance d between the successive conductor edges located on each side of the coil is at least 26 field-conducting, magnetically-conductive material arranged in supporting relationship to said coil sections in such manner as to leave at least the effective sides of the said sections which face the work uncovered by said material, the resultant permeability a res of the said material being not more than 10.
  • a fiat-shaped induction coil adapted to receive thin sheet, strip and the like work for inductively heating it, said coil including conductor sections adapted to lieon each side of the work with those on either side parallel with one another and parallel with those on the opposite side and including joining sections adapted to lie in the region of the work edges, the said conductor sections being spaced so that the distance between the successive conductor edges located on each side of the coil is at least 25, the said conductor sections being embedded in a field-conducting magnetically-conductive material comprising a hardenable plastic compound incorporating finely divided iron powder so as to leave the effective sides of the said sections which face the work uncovered by the said material, the resultant permeability a res of the said material being not more than 10.
  • An induction coil as claimed in claim 3, comprising an interior layer covering the said faces of the said sections which are intended to face the work, said layer comprising a hardenable plastic incorporating non-ferromagnetic, electrically non-conducting, anti-abrasive material.
  • An induction coil as claimed in claim 3, comprising an interior layer covering the said faces of the said sections which are intended to face "the work, said layer 5 comprising a hardenable plastic incorporating quartz meal.
  • a method of inductively heating relatively thin sheet, strip or the like work of large surface area which consists in producing a plurality of separate magnetic fields each about a difierent conductor-section of at least one flat induction coil which embraces the work with the said sections extending transversely of the work and being partially embedded in a substance which conducts the magnetic fields, travelling the strip and the coil relatively to one another with the coil embracing the strip, and by a supply frequency not exceeding 103000 cycles per sec- UNITED STATES PATENTS 2,381,246 Baker et a1. Aug. 7, 1945 2,381,278 Gregory et a1. Aug. 7, 1945 2,777,041 Dustman Jan. 8, 1957 2,888,541 Netzer May 26, 1959 2,897,328 Alf et a1. July 28, 1961

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
US840162A 1958-09-19 1959-09-15 Method of and apparatus for inductively heating metal Expired - Lifetime US3041434A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3041434X 1958-09-19
DED28994A DE1084850B (de) 1958-09-19 1958-09-19 Verfahren und Vorrichtung zum induktiven Durchlauferwaermen von verhaeltnismaessig duennen metallischen Werkstuecken

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424886A (en) * 1966-10-27 1969-01-28 Ajax Magnethermic Corp Induction heating
US3547715A (en) * 1967-04-14 1970-12-15 Bror Rossander Method for surface hardening polygonal steel rods and product treated according to the method
US3965321A (en) * 1973-09-24 1976-06-22 Varta Batterie Aktiengesellschaft Drying of storage battery plates
US4321444A (en) * 1975-03-04 1982-03-23 Davies Evan J Induction heating apparatus
US4484048A (en) * 1981-07-10 1984-11-20 Cem Compagnie Electro-Mecanique Process and apparatus for the homogeneous, electromagnetic induction heating with transverse flux of conducting and non-magnetic flat products
US4518840A (en) * 1982-02-18 1985-05-21 Cem Compagnie Electro-Mecanique Method and apparatus for minimizing the power induced in a flat conducting product maintained in position electromagnetically without contact
US4531037A (en) * 1982-03-12 1985-07-23 Cem Compagnie Electro-Mecanique Process and means to control the average heating power induced in a flat conducting product maintained electromagnetically in position without contact
US4649249A (en) * 1985-09-13 1987-03-10 Rockwell International Corporation Induction heating platen for hot metal working
US4761527A (en) * 1985-10-04 1988-08-02 Mohr Glenn R Magnetic flux induction heating
US4788394A (en) * 1985-03-06 1988-11-29 N.V. Bekaert S.A. Multi-wire induction heating
US5397877A (en) * 1992-06-24 1995-03-14 Celes Device for the homogeneous inductive heating of metallic flat products on the move
US20120305548A1 (en) * 2010-02-19 2012-12-06 Nippon Steel Corporation Transverse flux induction heating device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2381278A (en) * 1942-11-05 1945-08-07 Westinghouse Electric Corp Inductive heating coil shielding
US2381246A (en) * 1942-10-31 1945-08-07 Westinghouse Electric Corp Induction heating coil
US2777041A (en) * 1953-05-21 1957-01-08 Lindberg Eng Co High frequency heat treating apparatus
US2888541A (en) * 1957-10-01 1959-05-26 Westinghouse Electric Corp Encapsulated induction heating coil structure
US2897328A (en) * 1957-03-23 1959-07-28 Deutsche Edelstahlwerke Ag Method of progressively heating sheet metal and an induction coil for performing the method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2381246A (en) * 1942-10-31 1945-08-07 Westinghouse Electric Corp Induction heating coil
US2381278A (en) * 1942-11-05 1945-08-07 Westinghouse Electric Corp Inductive heating coil shielding
US2777041A (en) * 1953-05-21 1957-01-08 Lindberg Eng Co High frequency heat treating apparatus
US2897328A (en) * 1957-03-23 1959-07-28 Deutsche Edelstahlwerke Ag Method of progressively heating sheet metal and an induction coil for performing the method
US2888541A (en) * 1957-10-01 1959-05-26 Westinghouse Electric Corp Encapsulated induction heating coil structure

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424886A (en) * 1966-10-27 1969-01-28 Ajax Magnethermic Corp Induction heating
US3547715A (en) * 1967-04-14 1970-12-15 Bror Rossander Method for surface hardening polygonal steel rods and product treated according to the method
US3965321A (en) * 1973-09-24 1976-06-22 Varta Batterie Aktiengesellschaft Drying of storage battery plates
US4321444A (en) * 1975-03-04 1982-03-23 Davies Evan J Induction heating apparatus
US4484048A (en) * 1981-07-10 1984-11-20 Cem Compagnie Electro-Mecanique Process and apparatus for the homogeneous, electromagnetic induction heating with transverse flux of conducting and non-magnetic flat products
US4518840A (en) * 1982-02-18 1985-05-21 Cem Compagnie Electro-Mecanique Method and apparatus for minimizing the power induced in a flat conducting product maintained in position electromagnetically without contact
US4531037A (en) * 1982-03-12 1985-07-23 Cem Compagnie Electro-Mecanique Process and means to control the average heating power induced in a flat conducting product maintained electromagnetically in position without contact
US4788394A (en) * 1985-03-06 1988-11-29 N.V. Bekaert S.A. Multi-wire induction heating
US4649249A (en) * 1985-09-13 1987-03-10 Rockwell International Corporation Induction heating platen for hot metal working
US4761527A (en) * 1985-10-04 1988-08-02 Mohr Glenn R Magnetic flux induction heating
US5397877A (en) * 1992-06-24 1995-03-14 Celes Device for the homogeneous inductive heating of metallic flat products on the move
US20120305548A1 (en) * 2010-02-19 2012-12-06 Nippon Steel Corporation Transverse flux induction heating device
US10292210B2 (en) * 2010-02-19 2019-05-14 Nippon Steel & Sumitomo Metal Corporation Transverse flux induction heating device
US10327287B2 (en) * 2010-02-19 2019-06-18 Nippon Steel & Sumitomo Metal Corporation Transverse flux induction heating device

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NL243545A (fi) 1900-01-01

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