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WO2025238668A1 - Appareil de chauffage par induction de métaux ferromagnétiques - Google Patents

Appareil de chauffage par induction de métaux ferromagnétiques

Info

Publication number
WO2025238668A1
WO2025238668A1 PCT/IT2025/050107 IT2025050107W WO2025238668A1 WO 2025238668 A1 WO2025238668 A1 WO 2025238668A1 IT 2025050107 W IT2025050107 W IT 2025050107W WO 2025238668 A1 WO2025238668 A1 WO 2025238668A1
Authority
WO
WIPO (PCT)
Prior art keywords
electromagnet
current
magnetic field
magnetic
component
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.)
Pending
Application number
PCT/IT2025/050107
Other languages
English (en)
Inventor
Antonio Morandi
Massimo Fabbri
Francesco MIMMI
Emiliano GUERRA
Mattia SIMONAZZI
Giacomo RUSSO
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.)
Universita di Bologna
Original Assignee
Universita di Bologna
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 Universita di Bologna filed Critical Universita di Bologna
Publication of WO2025238668A1 publication Critical patent/WO2025238668A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
    • H05B6/101—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • H05B6/06—Control, e.g. of temperature, of power
    • 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

Definitions

  • the present invention relates to the field of devices for industrial heating of ferromagnetic semi-finished or finished products that are below the Curie temperature.
  • the invention includes an apparatus and method for induction heating.
  • the depth of heating of the object depends on the so-called penetration depth, that is, the depth, starting from the surface of the material, in which the intensity of the induced current is reduced to 1/e of the intensity of the current on the surface of the material.
  • This penetration depth can be expressed by the formula: 8 where 6 is the penetration depth, p is the resistivity of the material, f is the frequency of the induced current, po is the magnetic permeability of the air and p r the relative magnetic permeability of the material to be heated.
  • the penetration depth 6 is controlled by varying the frequency f; for example, when only the surface of the artifact is to be heated, a high frequency is adopted, while a lower frequency is used to heat even the innermost portions of the object.
  • a frequency for example, when only the surface of the artifact is to be heated, a high frequency is adopted, while a lower frequency is used to heat even the innermost portions of the object.
  • the coupling between the electromagnet and the object to be heated gets worse, and very high magnetic fields are required, which in turn necessitates high currents; for this reason, if the material to be heated has a high relative magnetic permeability, it is difficult to conciliate deep heating of the object with acceptable electromagnetic coupling.
  • induction heating often cannot be used for materials whose magnetic permeability is high, e.g., above 1; therefore, for the treatment of magnetic steel semi-finished products of industrial interest, i.e., thick slabs or blooms with minimum dimensions in the range of tens of centimeters, heating by gas or resistance ovens is the commonly adopted solution.
  • These heating systems often take advantage of nonrenewable energy sources, e.g., fuel gas, and have certain disadvantages in turn, e.g., related to the fact that the thermal energy is transmitted to the object necessarily through the latter's surface, or the large amount of carbon dioxide produced by combustion.
  • WO2014088423 describes an apparatus comprising an AC coil, made of copper, powered with alternating current, arranged around the object to be heated and a DC coil made of superconducting material, powered with direct current and arranged in turn around the AC coil.
  • the AC coil generates an alternating magnetic field that induces currents in the object suitable for heating it, while the DC coil generates a continuous magnetic field such that the magnetic material of the object is saturated, so as to reduce its magnetic permeability and increase the penetration depth, facilitating deep heating.
  • EP2441849 describes an apparatus comprising a DC magnetic field generator conformed as a coil of superconducting material, inside which an object to be treated is placed.
  • the apparatus also includes an AC magnetic field generator by which the object is heated by induction only in a surface layer of predetermined thickness, the depth of which depends on the frequency chosen to feed the AC magnetic field generator.
  • this apparatus is used only for surface treatments and does not allow inducing currents inside the entire object to heat it internally as well.
  • WO2018172929 describes an apparatus for induction heating of two ferromagnetic products, comprising a first winding supplied with alternating current configured to generate a first alternating magnetic field that affects the first product; a winding powered with direct current, to generate a magnetic field capable of regulating the magnetic permeability of the two products.
  • the apparatus according to WO2018172929 also includes a second alternating current-fed winding configured to generate a second magnetic field that affects the second product; the two alternating current-fed windings are made and powered so that the respective alternating magnetic fields generated by them have the same direction, but opposite senses.
  • One object of the present invention is to improve apparatuses and methods of a known type for induction heating an object made of magnetic material, particularly a steel object, for temperatures below the Curie temperature, increasing the temperature even in depth, preparing the object for certain processing, such as hot plastic deformation processing, or influencing its magnetic properties during heat treatment.
  • Another object is to provide an apparatus for induction heating of an object in which the electromagnetic coupling between AC and DC components is zero, or at least very low, particularly by simplifying the magnetic system and reducing the critical voltages induced on the DC winding.
  • a further object is to provide an apparatus for induction heating an object, which is inexpensive, simple, compact, and efficient.
  • the single electromagnet required for generating both the DC and AC magnetic fields can be a resistive electromagnet made by conventional technology, such as by water-cooled copper conductors, or it can be an electromagnet made by superconducting technology.
  • Figure 1 schematically depicts the configuration that is the subject of this patent, in which a steel billet (A) is placed inside a single electromagnet (1) that generates both AC and DC electromagnetic fields; two containment shields (6, 7) are also shown.
  • Figure 2 shows a schematic view of the electrical circuit for powering the electromagnet (4) of the induction heater from the power source (2) by means of a power converter (3); it should be noted that in this schematic the equivalent resistance of the magnet is omitted for simplicity.
  • Figure 3 shows two periods of a waveform composed of a DC and a sinusoidal AC component.
  • the amplitude of the DC component is higher than that of the AC component, but it could also be the same or lower.
  • amplitude of the DC component and amplitude and frequency of the harmonic components may vary depending on the requirements of the part's processing.
  • the waveform shown in Figure 3 is achievable, for example, with multilevel DC/AC converters, usually called “Modular Multilevel converters (MMCs)" or "Cascaded H-bridge".
  • MMCs Modular Multilevel converters
  • Figure 4 shows three periods of a square wave with a nonzero mean value over the period, which then has DC component and various harmonics (thus various AC components at frequencies multiple of the fundamental). This current waveform is easier to generate because it does not require filtering stages or multilevel architectures. In fact, a conventional single-phase or "full bridge" inverter - controlled by varying the duty cycle - is sufficient.
  • FIG. 5 shows an alternative design configuration of the invention. While the current I is controlled similarly to what has already been described with reference to the system in Figure 1, the electromagnet (5) in which this current is placed produces a magnetic field (B) that passes through the steel plate or other ferromagnetic object (C) in a transverse direction and not axially as in Figure 1.
  • This configuration may include one or more electromagnets facing the semi-finished product to be heated; in the embodiment depicted there are two electromagnets, one below and the other above the object, carrying the same current I.
  • the electromagnet is configured as one or more solenoidal inductors, coaxial with a billet, however, it should be noted that this embodiment is shown as an example only, this term being understood to include configurations with a winding, or a coil, or a solenoid, among others.
  • electromagnets can generally be configured so that they surround the object to be heated, or so that the magnetic field they generate affects the object from one or more sides.
  • Containment shields (6, 7) are generally provided around the electromagnet, which are of the cryogenic type in the case where the electromagnet (1) is of the superconducting type.
  • the different configurations can be applied for heating parts of different shapes such as raw products such as slabs, blooms and slabs, or finished products such as bars, profiles, other structural shapes, rails, rods, plates, sheets, strips, tubes, rings, wires, coils, tapes, etc.
  • raw products such as slabs, blooms and slabs
  • finished products such as bars, profiles, other structural shapes, rails, rods, plates, sheets, strips, tubes, rings, wires, coils, tapes, etc.
  • embodiments of the invention are possible that include separate windings, e.g., top and bottom, for the application of a transverse field including DC and AC components.
  • an AC/AC type converter implementable through different architectures, receives input power from the grid (or from a different source) and acts internally to control the current I in the ways previously described.
  • Periodic waveforms with nonzero mean value can also be obtained from DC/DC switching converters in which the output current has a high harmonic content (thus is not filtered), and the switching frequency corresponds to the fundamental AC component or its multiples.
  • usable switching converters can have very varied architectures. This allows design complexity to be limited and costs to be kept down considerably.

Landscapes

  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Induction Heating (AREA)

Abstract

L'invention concerne un appareil de chauffage par induction de matériaux ferromagnétiques dans lequel un seul électroaimant est utilisé pour la génération simultanée de champs CA et CC.
PCT/IT2025/050107 2024-05-14 2025-05-13 Appareil de chauffage par induction de métaux ferromagnétiques Pending WO2025238668A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT202400010867 2024-05-14
IT102024000010867 2024-05-14

Publications (1)

Publication Number Publication Date
WO2025238668A1 true WO2025238668A1 (fr) 2025-11-20

Family

ID=92208825

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IT2025/050107 Pending WO2025238668A1 (fr) 2024-05-14 2025-05-13 Appareil de chauffage par induction de métaux ferromagnétiques

Country Status (1)

Country Link
WO (1) WO2025238668A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB929844A (en) * 1960-02-05 1963-06-26 Soc De Traitements Electrolytiques Et Electrothermiques Improvements in methods and equipments for induction heating
US20050065901A1 (en) * 2003-07-09 2005-03-24 Board Of Regents, The University Of Texas System Methods and systems for simultaneous multiple frequency voltage generation
US20060231549A1 (en) * 2005-04-19 2006-10-19 Kisner Roger A Thermal and high magnetic field treatment of materials and associated apparatus
EP2441849A2 (fr) 2010-10-14 2012-04-18 Eaton Corporation Traitement et appareil thermomagnétique sélectif de profondeur de pénétration de trempe
WO2014088423A1 (fr) 2012-12-04 2014-06-12 Sinvent As Appareil et procédé pour chauffage par induction de matériaux magnétiques
WO2018172929A1 (fr) 2017-03-22 2018-09-27 Alma Mater Studiorum - Universita' Di Bologna Appareil et procédé de chauffage par induction

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB929844A (en) * 1960-02-05 1963-06-26 Soc De Traitements Electrolytiques Et Electrothermiques Improvements in methods and equipments for induction heating
US20050065901A1 (en) * 2003-07-09 2005-03-24 Board Of Regents, The University Of Texas System Methods and systems for simultaneous multiple frequency voltage generation
US20060231549A1 (en) * 2005-04-19 2006-10-19 Kisner Roger A Thermal and high magnetic field treatment of materials and associated apparatus
EP2441849A2 (fr) 2010-10-14 2012-04-18 Eaton Corporation Traitement et appareil thermomagnétique sélectif de profondeur de pénétration de trempe
WO2014088423A1 (fr) 2012-12-04 2014-06-12 Sinvent As Appareil et procédé pour chauffage par induction de matériaux magnétiques
WO2018172929A1 (fr) 2017-03-22 2018-09-27 Alma Mater Studiorum - Universita' Di Bologna Appareil et procédé de chauffage par induction

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