US2845377A - Method for the inductive hardening of elongated workpieces - Google Patents

Method for the inductive hardening of elongated workpieces Download PDF

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Publication number
US2845377A
US2845377A US569007A US56900756A US2845377A US 2845377 A US2845377 A US 2845377A US 569007 A US569007 A US 569007A US 56900756 A US56900756 A US 56900756A US 2845377 A US2845377 A US 2845377A
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United States
Prior art keywords
inductor
quenching
hardening
temperature
inductors
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Expired - Lifetime
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US569007A
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English (en)
Inventor
Seulen Gerhard
Connert Winfried
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Deutsche Edelstahlwerke AG
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Deutsche Edelstahlwerke AG
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    • 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
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
    • 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
    • H05B6/40—Establishing desired heat distribution, e.g. to heat particular parts of workpieces
    • 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

  • the present invention relates to a method of and apparatus for hardening elongated workpieces by inductive heating and quenching by the forward-feed method, i. e., the method in which the hardening is carried out progressively along the workpiece, the inductor and the workpiece moving relatively to one another, the inductor progressively heating and a quenching device progressively quenching the workpiece.
  • the inductor may be a coil and the quenching device a ring from which the quenching medium is sprayed, and either the workpiece may be moved with respect to the inductor or the inductor may be moved with respect to the workpiece.
  • the invention is well suited for hardening cold rolls, i. e., rolls intended for cold rolling.
  • the temperature suitable for hardening is reached where the workpiece is at the end of the inductor adjacent the quenching device. Consequently the time lag between the time the workpiece reaches this temperature and the time the quenching takes place must necessarily be comparatively short, a requirement which also imposes itself if heat penetration into the core of the material is to be avoided and hardening is to take effect in the surface layer only.
  • the temperature time function is predetermined and depends upon the re quired rate of travel and the distance which must be maintained between the induction coil and the quenching device.
  • the apparatus proposed by the present invention avoids these troublesome difiiculties and permits a reliable and effective heat treatment, even in the case of cold rolls, by the induction heating method, hardening being effected by subsequent quenching at the end of a variably controllable time lag during which temperature is correctly maintained.
  • at least two electrically independently controllable and variable inductors are used, arranged axially one behind the other.
  • a quenching spray is provided to follow the last inductor.
  • two inductors will be sufiicient, the first to heat the surface of the workpiece to the temperature required for hardening, and the second to hold this temperature substantially constant for the required period of time before quenching takes place.
  • variable electrical control of the inductors it may be an advantage, in addition, to provide for adjustability of the axial distances between the inductors, and possibly also of the quenching device from the inductors and continuous adjustment may be achieved.
  • the arrangement may be such that the inductors are fed from separate sources of power, which may be of different frequency, each capable of being regulated.
  • a single source of supply only may be employed and the induction units operated in parallel.
  • At least one of the two supply circuits will then include a variable inductance, such as an auto-transformer or a choke.
  • the two inductors may be wound with a different number of ampere-turns, irrespective as to whether they are being fed from one or several sources of supply.
  • the electrical arrangement affords a wide range of control. More particularly, it makes it possible to switch off the leading inductor as it rides over the edge of the workpiece while the following coil or coils continue in operation. Thus it becomes possible to avoid overheating of the edge of a cold roll or of insufiiciently hardening it.
  • the apparatus is operated with two or more induction coils fed from a single source of electrical power it is electrically advantageous, when switching off one of the inductors, to arrange for suitable switchgear in the exciter circuit of the generator to interrupt the medium frequency circuit for the duration of the switching operation.
  • suitable switchgear in the exciter circuit of the generator may consist, for instance, of D. C. relays, or control grids in the case of electronic exciter devices.
  • Fig. 1 shows the cold roll 1 which, for the purpose of its heat treatment, is moved axially under the heating and quenching units and which may at the same time perform a rotary motion in the direction of the arrow 2.
  • the apparatus operates while the axial movement of the cold roll 1 under the stationary induction and quenching units proceeds in the'direction of the arrow 3.
  • the workpiece it is equally possible to arrange for the workpiece to be stationary, and to carry out the hardening operation by moving both the inductors and the quenching spray in an upward direction beginning at the lower edge 4 of the roll and proceeding in the direction of the arrow 3.
  • the induction heating unit consists of the inductor 6 which is preferably narrow in axial extent.
  • the object of this inductor is to raise the temperature of the surface layers within its inductive range to the desired hardening temperature, practically immediately.
  • the inductor 7 which is arranged to follow the inductor 6 in an axial direction may have a greater axial length than the latter. It'is electrically so designed as to maintain the temperature induced by the inductor 6. Whereas it will be generally necessary for the purpose of achieving the desired efiect to wind the inductor 6 in several layers the winding of inductor 7 will usually require a single layer only. It is nevertheless quite possible to feed the inductor 6 with a voltage which allows its windings to be restricted to a single layer despite its short axial length.
  • the quenching unit 8 which performs the hardening by spraying the liquid quenching medium such as water, brine, an emulsion, or the like, on to the surface of the roll in the direction of the arrow 9.
  • the intervening distances 1t ⁇ and 11 are controllably variable so that any desired axial displacement of the inductors in relation to one another may be effected.
  • the design may be such that the quenching unit is stationary whereas both inductors 6 and 7 are independently displaceable in an upward direction, or alternatively, the inductor 6 maybe the fixed element whilst inductor 7 and quenching unit 8 may be each displaced independently in a downward direction relatively to unit 6.
  • the inductor 7 may also be so designed electrically that the surface temperature on the roll created by the inductor 6 is slightly increased by unit 7. Alternatively, it is also possible to arrange for the effective intensity of induction of unit 7 to allow of a slight falling off of the temperature as the workpiece passes through it. It is also possible to construct the inductor 7 in such manner that the temperature on the surface of the moving workpiece undergoes slight fluctuating changes as it passes beneath it.
  • the inductor 6 is connected directly or through an intermediate transformer to the source of supply, generally a rotary generator 12 which delivers a current of raised frequency.
  • a condenser battery 13 serves to compensate for reactive currents in the load circuit.
  • Voltage regulation of the generator 12 permits the effective power of the inductor 6 to be variably controlled as desired.
  • regulation of the generator 12 may also be effected by means of devices affecting the current or the wattage supplied by the generator.
  • the condensers 13 schematically indicated in Fig. 1 may be jointly or severally controlled by switches to permit of suitable adjustments to be made to correspond with any set of operational circumstances.
  • the inductor 7 is connected directly or through an intermediate transformer with the source of supply 14 which may generally be provided by a rotary medium frequency generator.
  • the condenser battery 15 similarly serves to eliminate any reactive currents set up in the load circuit. This condenser battery is again preferably provided with switch elements. Regulation of the power supply at 14 may be carried out by similar means as above described in the case of generator 12.
  • the wattage and frequencies of both sources of supply 12 and 14 may be similar. In special cases, however, it may be an advantage to work with dissimliar frequencies and power.
  • the frequency of the source 12 might be lower than that supplied by the source 14 and the elfect obtained of securing a greater depth of penetration of the surface layers of the roll which are within the inductive range of the inductor 6.
  • the high temperature of the surface layers of the roll will assure similar penetration at the higher frequency of the source 14 without risk of causing the core to be overheated at the same time.
  • the power output of the two sources may also be dissimilar inasmuch as, for instance, generator 12 may have a high power output to ensure that the temperature of the relative surface layers of the roll is raised rapidly to the desired degree, whereas the output of generator 14 may be less since the heating element(s) supplied by this generator serves only to maintain the temperature that has been reached or at least to vary it only slightly. Regulation of the exciter windings 16 and 17 of the two generators permits the power output of both generators to be continuously varied and controlled within any desired limits.
  • Power switches 18 and 19 in the load circuits may be provided to permit the inductors 6 and 7 to be cut out and cut in independently the one from the other at any time or in any position they may have reached in relation to the workpiece, as may be deemed expedient. These power switches indicated schematically at 18 and 19 may be in the form of two-pole power switches. Instead of placing them into the load circuit proper they may be arranged immediately behind the generators as shown, for instance at 19.
  • Fig. 2 refers to an arrangement where both induction units are powered from one and the same source of supply.
  • the two axially arranged inductors are again indicated by 6 and 7.
  • the inductor 6 which is responsible for raising the surface temperature rapidly to the desired value is connected to the common source of A. C.
  • the condensers at 22 in this case again serve to compensate for reactive currents appearing in the load circuit.
  • Switch elements should again be provided to adapt the condenser capacity to the inductive load.
  • the inductor '7 is connected with the generator via the control element 23. This inductor is likewise compensated by a condenser battery of suitable capacity.
  • the switch 25 serves to cut out or cut in the heating circuit comprising the inductor '7 and the condenser battery 24.
  • the terminal pressure supplied by the generator can be regulated. When the switch 21 is closed the same pressure is operative across the condenser battery 22 and the inductor 6.
  • the pressure across the condenser battery 24 and the inductor '7 depends upon the pressure drop across the control element 23. For instance, if a large inductance is introduced at 23 the pressure across inductor 7 will become correspondingly small. Since output depends upon the operating pressure across the inductors the heating effect upon the surface elements of the roll may be differentially controlled in ratio with the difference obtaining between the pressures across the two inductors although both are powered from the same source of supply.
  • the control element 23 is shown in the form of a variable choke. Such variable chokes are available with displaceable or tilting laminated iron cores.
  • variable chokes may be replaced by one having its windings suitably tapped.
  • the latter type of choke permits the output of the inductor 7 to be controlled step by step by switching successively from tapping to tapping.
  • the change-over from tapping to tapping may be effected by screw type strap links, by means of relays, or by means of mechanically operated change-over switches.
  • a choke 23 may be altogether dispensed with in favor of a tapped auto-transformer or of a normal transformer having both primary and secondary tapped. The necessary connections on such transformers may also be made with the help of strap links, relays, or change-over switches.
  • the condenser battery 24 may also be placed immediately behind the switch 25 so as to bring the control element into the load circuit proper.
  • inductor 6 Since it will be generally necessary for the thermal output of inductor 6 to be higher within a shorter axial length than that of inductor 7, provision may be made in the electrical design to meet this need by giving inductor 6, for operation in parallel, a much smaller number of turns than the inductor 7. Pressure across both inductors being equal this means that power input at unit 6 will he very much greater than at unit 7.
  • the control element 23 may, in such a case, be comparatively small as 6 it will merely serve the purpose of providing a stepped or continuously variable fine adjustment of the power differential between the two inductors.
  • an adjustable constant-voltage device should be included in the circuit. Such a device would be necessary to ensure that the voltage is reliably maintained at a constant level irrespective of load conditions and the position of switches 21 and 25.
  • the exciting current in the exciter circuit 26 is first cut out by a D. C. relay, not shown in the drawing, or, in the case of electronic control, by means of a control grid.
  • a voltage or time operated relay 21 is opened as a result thereof and the exciter circuit 26 is then reclosed.
  • Inductor 7 may be disconnected by means of relay 25 in a similar way.
  • a forward feed process of surface hardening ferrous rolls by inductive heating and quenching, which comprises rapidly heating the rolls by means of at least one leading inductor to the temperature suitable for hardening, maintaining the said temperature by means of a following inductor, and then quenching the rolls and controlling the leading inductor independently of the following inductor and in timed relation to the relative movement so that the heating effect of the said leading inductor is reduced when an edge of the workpiece is in the effective range thereof and whilst the following inductor or heater remains in operation.
  • leading and following inductors are supplied by a common source of electrical power and are arranged in parallel and are independently controllable.

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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)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • General Induction Heating (AREA)
US569007A 1955-03-18 1956-03-02 Method for the inductive hardening of elongated workpieces Expired - Lifetime US2845377A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DED20059A DE1036886B (de) 1955-03-18 1955-03-18 Vorrichtung zum induktiven Haerten langgestreckter Werkstuecke

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US (1) US2845377A (de)
AT (1) AT193418B (de)
DE (1) DE1036886B (de)
FR (1) FR1148889A (de)
GB (1) GB780356A (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2905798A (en) * 1958-09-15 1959-09-22 Lindberg Eng Co Induction heating apparatus
US3137596A (en) * 1962-10-03 1964-06-16 Paul M Unterweiser Method for hardening a nitrided steel
US3144365A (en) * 1963-07-10 1964-08-11 Ingersoll Rand Co Method of heat treating elongated steel articles
US3196244A (en) * 1962-01-11 1965-07-20 Deutsche Edelstahlwerke Ag Inductor for the surface heating of gear wheels
US3222229A (en) * 1960-07-14 1965-12-07 Voest Ag Process of hardening alloy steels
US3231434A (en) * 1962-12-22 1966-01-25 Deutsche Edelstahlwerke Ag Method of surface hardening steel bodies of revolution
US3488236A (en) * 1966-12-22 1970-01-06 Beaver Precision Prod Method and apparatus for heat treating a metallic workpiece
US3658605A (en) * 1968-09-18 1972-04-25 Japan National Railway Method of induction hardening for improving fatigue strength of boundary of heated zone
WO1990009458A1 (en) * 1989-02-13 1990-08-23 A.E. Bishop & Associates Pty. Ltd. Improvements in scanning induction hardening
US5808280A (en) * 1994-12-09 1998-09-15 Cidelcem Industries Device for induction heating of a receptable and process for controlling such a device
US20090049804A1 (en) * 2006-03-14 2009-02-26 Ki Seok Choi Portable Aluminum Foil Sealing Apparatus
US20120125919A1 (en) * 2009-07-30 2012-05-24 Neturen Co., Ltd. Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method
US20140144904A1 (en) * 2011-04-07 2014-05-29 Neturen Co., Ltd. Induction heating device, induction heating equipment, induction heating method, and heat treatment method

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1137151B (de) * 1961-07-28 1962-09-27 Siemens Ag Anordnung zur Begrenzung schaedlicher Spannungsoberwellen
JPS5317509A (en) * 1976-08-03 1978-02-17 Nippon Kokan Kk <Nkk> Method and apparatus for induction heating of metallic material
DE3669044D1 (de) * 1985-12-19 1990-03-22 Bbc Brown Boveri & Cie Verfahren zum zonengluehen eines metallischen werkstuecks.
DE69837419T2 (de) 1997-06-11 2007-12-20 Matsushita Electric Industrial Co., Ltd., Kadoma Einrichtung zur induktiven Erwärmung von Flüssigkeiten
DE102005061670B4 (de) * 2005-12-22 2008-08-07 Trithor Gmbh Verfahren zum induktiven Erwärmen eines Werkstücks

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1646498A (en) * 1925-12-29 1927-10-25 Gen Electric Electric heating
US2202758A (en) * 1934-09-24 1940-05-28 Ohio Crankshaft Co Apparatus for progressive heat treatment
US2444259A (en) * 1944-09-21 1948-06-29 Gen Electric Method of high-frequency induction heating
US2590546A (en) * 1949-07-25 1952-03-25 Westinghouse Electric Corp Heat-treatment of irregular metallic objects

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE569351C (de) * 1926-12-30 1933-02-02 Aeg Verfahren und Vorrichtung zum Erhitzen von ferromagnetischen Werkstoffen durch die Werkstoffe durchsetzende magnetische Wechselfelder

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1646498A (en) * 1925-12-29 1927-10-25 Gen Electric Electric heating
US2202758A (en) * 1934-09-24 1940-05-28 Ohio Crankshaft Co Apparatus for progressive heat treatment
US2444259A (en) * 1944-09-21 1948-06-29 Gen Electric Method of high-frequency induction heating
US2590546A (en) * 1949-07-25 1952-03-25 Westinghouse Electric Corp Heat-treatment of irregular metallic objects

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2905798A (en) * 1958-09-15 1959-09-22 Lindberg Eng Co Induction heating apparatus
US3222229A (en) * 1960-07-14 1965-12-07 Voest Ag Process of hardening alloy steels
US3196244A (en) * 1962-01-11 1965-07-20 Deutsche Edelstahlwerke Ag Inductor for the surface heating of gear wheels
US3137596A (en) * 1962-10-03 1964-06-16 Paul M Unterweiser Method for hardening a nitrided steel
US3231434A (en) * 1962-12-22 1966-01-25 Deutsche Edelstahlwerke Ag Method of surface hardening steel bodies of revolution
US3144365A (en) * 1963-07-10 1964-08-11 Ingersoll Rand Co Method of heat treating elongated steel articles
US3488236A (en) * 1966-12-22 1970-01-06 Beaver Precision Prod Method and apparatus for heat treating a metallic workpiece
US3658605A (en) * 1968-09-18 1972-04-25 Japan National Railway Method of induction hardening for improving fatigue strength of boundary of heated zone
WO1990009458A1 (en) * 1989-02-13 1990-08-23 A.E. Bishop & Associates Pty. Ltd. Improvements in scanning induction hardening
US5808280A (en) * 1994-12-09 1998-09-15 Cidelcem Industries Device for induction heating of a receptable and process for controlling such a device
US20090049804A1 (en) * 2006-03-14 2009-02-26 Ki Seok Choi Portable Aluminum Foil Sealing Apparatus
US20120125919A1 (en) * 2009-07-30 2012-05-24 Neturen Co., Ltd. Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method
US9534267B2 (en) * 2009-07-30 2017-01-03 Neturen Co., Ltd. Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method
US10648052B2 (en) 2009-07-30 2020-05-12 Neturen Co., Ltd. Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method
US20140144904A1 (en) * 2011-04-07 2014-05-29 Neturen Co., Ltd. Induction heating device, induction heating equipment, induction heating method, and heat treatment method
US10057945B2 (en) * 2011-04-07 2018-08-21 Neturen Co., Ltd. Induction heating device, induction heating equipment, induction heating method, and heat treatment method
US10952288B2 (en) 2011-04-07 2021-03-16 Neturen Co., Ltd. Induction heating device, induction heating equipment, induction heating method, and heat treatment method
US11729868B2 (en) 2011-04-07 2023-08-15 Neturen Co., Ltd. Induction heating device, induction heating equipment, induction heating method, and heat treatment method

Also Published As

Publication number Publication date
GB780356A (en) 1957-07-31
DE1036886B (de) 1958-08-21
FR1148889A (fr) 1957-12-17
AT193418B (de) 1957-11-25

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