EP0156545A2 - Wärmebehandlungsverfahren mittels selbstregulierender Heizvorrichtung - Google Patents

Wärmebehandlungsverfahren mittels selbstregulierender Heizvorrichtung Download PDF

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Publication number
EP0156545A2
EP0156545A2 EP85301501A EP85301501A EP0156545A2 EP 0156545 A2 EP0156545 A2 EP 0156545A2 EP 85301501 A EP85301501 A EP 85301501A EP 85301501 A EP85301501 A EP 85301501A EP 0156545 A2 EP0156545 A2 EP 0156545A2
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EP
European Patent Office
Prior art keywords
article
temperature
layer
magnetic material
heat
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.)
Granted
Application number
EP85301501A
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English (en)
French (fr)
Other versions
EP0156545A3 (en
EP0156545B1 (de
Inventor
Rodney L. Derbyshire
Paul F. Busch
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.)
Metcal Inc
Original Assignee
Metcal Inc
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 Metcal Inc filed Critical Metcal Inc
Priority to AT85301501T priority Critical patent/ATE56476T1/de
Publication of EP0156545A2 publication Critical patent/EP0156545A2/de
Publication of EP0156545A3 publication Critical patent/EP0156545A3/en
Application granted granted Critical
Publication of EP0156545B1 publication Critical patent/EP0156545B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • 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
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes

Definitions

  • heat treatment In the field of metallurgy, heat treatment is employed to achieve numerous results. In a broad sense heat treatment includes any thermal treatment intended to control properties. With respect to metal alloys, such as steel, tempering and annealing are particularly well known methods of heat treatment.
  • Heat treating to achieve a desired alteration of properties is often times a process that is performed optimally at a specific temperature.
  • temperature chambers and complex heater/thermostat arrangements are generally employed.
  • heat treating is performed before an article is sent to the field--the properties of the article being defined at the mill,factory, or other producing facility.
  • it may be deemed desirable to effectuate changes in the metallurgical properties of the article in the field, or in situ, without the need for a temperature chamber, oven or heater-thermostat arrangement.
  • an article of metal can be heat treated to effectuate property changes therein in the field by an autoregulating heater.
  • the autoregulating heater is disposed along the portions of the article to be heat treated, thereby achieving the object of local heat treating.
  • the autoregulating heater includes at least a first magnetic material which changes sharply in skin depth between temperatures below and above an autoregulating temperature (AR).
  • AR autoregulating temperature
  • the AR temperature is closely related to and determined by the Curie temperature.
  • the changing skin depth results in corresponding variations in the level of heat produced in response to an a.c. current being applied to the first magnetic material.
  • the heat generated is inversely related to the temperature of the heater. The inverse relationship between the temperature of the heater and the heat generated thereby renders the heater autoregulating or self-regulating so that a controlled application of heating can be effected to heat treat a metal article in the field to a temperature determined by an autoregulating heater.
  • a.c.current flows primarily through a shallow depth of the magnetic layer below the AR temperature and into the low resistance non-magnetic layer above the.AR temperature, thereby greatly reducing heat generation at temperatures above theAR temperature.
  • Autoregulation at a temperature substantially corresponding to the desired heat treatment temperature is achieved at generally several degrees less than the Curie point of the magnetic layer.
  • a shielding effect is achieved for applications-in which the generation of signals outside the heater is not desired.
  • a plurality of magnetic layers are provided in an autoregulating heater that is disposed along and transfers heat to an article in the field that is to be heat treated.
  • an article may be heat treated at any of several temperatures.
  • heat treating such as tempering
  • Interposing a low resistance non-magnetic layer between and in contact with two magnetic layers may also be employed in the autoregulating heater to enable selectable temperature regulation in heat treating an article in the field.
  • any one of the autoregulating heaters set ⁇ forth above into the article or portion thereof that is to be heat treated.
  • the article-heater may be installed and, as required, the heater may be actuated by connecting a.c. current thereto to effectuate heat treatment in the field.
  • the heater may be fixedly imbedded in the article or may, alternatively, be integrally formed along the article.
  • the_pipe itself may comprise a magnetic layer of the autoregulating heater.
  • the invention contemplates relieving stress in articles or portions thereof which have been over-hardened in the field or which have been rendered brittle due to exposure to radiation or which have been heavily work hardened due to machining or which have undergone fatigue cycling while in the field which might lead to fracture or failure.
  • the invention contemplates heat treating tooled steel in the field and surface treating an article by nitriding or carborizing at a proper heat treating temperature.
  • a metal pipe section 100 is shown coupled between two other pipe sections 102 and 104.
  • the pipe section 100 is located along a pipeline 106 which, preferably, carries a fluid-such as oil or gas.
  • a fluid-such as oil or gas When so employed, the pipe section 100 is often times exposed to numerous conditions that may adversely affect the structure and properties thereof. For example, thermal changes may result in stressing the pipe section 100.
  • welds along the pipe section 100 may require stress relief after field welding.
  • an autoregulating heater 110 for heat treating the pipe section 100 in the field (in situ) is provided. In this regard, it must be realized that accurate heat treating control is important to avoid overheating or underheating which seriously detracts from the heat treatment.
  • the autoregulating heater 110 may be of various forms-- in each case the autoregulating heater 110 (a) being disposed along the pipe section 100 (or other workpiece) in the field along a length that is to be heat treated and (b) regulating at a temperature appropriate to heat treat the section 100 in the field.
  • the autoregulating heater 100 is of a nature which permits the maintaining of a uniform temperature locally along the length L of the pipe section 100 to be heat treated.
  • an a.c. current source 112 is shown.
  • the source 112 provides a "constant" current which, preferably, is at a selected fixed frequency.
  • the current is applied to enable the current to flow through a heating structure 114.
  • heating structure 114 Several embodiments of heating structure 114 are illustrated in Figures II and III.
  • the pipe section 200 is shown encompassed by a single magnetic layer 202.
  • the magnetic layer 202 has a clamp member 204 which enables the magnetic layer 202 to be wrapped and held around the pipe section 200 in the field.
  • the magnetic layer 202 has a prescribed resistivity ( ⁇ ) and a permeability ( ⁇ ) which varies sharply--at points above and. below an autoregulation (AR) temperature.
  • the AR temperature is typically a few degrees lower than the conventionally defined-- Curie temperature of the magnetic layer 200.
  • a sample table of magnetic materials is set forth below.
  • the permeability (. ⁇ ) of the magnetic layer 202 corresponds substantially to the effective permeability well below the AR temperature and approximately one above the AR temperature.
  • This variation in permeability changes the skin depth which is proportional to That is, as temperature increases to above the AR temperature, the permeability falls to one from, for example, 400 which results in the skin depth increasing by a factor of 20.
  • the increase in skin depth results in an increase in the cross-section through which a.c. current is primarily confined.
  • a.c. current distribution relative to depth in a magnetic material is an exponential function, namely current falls off at the rate of 1-e tt /S.D. where t is thickness and S.D. is skin depth.
  • a.c. current is applied to the magnetic layer 202 the current is confined to a shallow depth about the outer periphery thereof when the temperature of the imagnetic layer 202 is below the AR temperature thereof. As the temperature increases and exceeds the AR temperature, the skin depth spreads to deeper thicknesses and current thereby flows through a larger cross-section. The heat generated is thereby reduced.
  • the magnetic layer 202 is thermally conductive, the heat generated thereby when the skin depth is shallow is transferred to the pipe section 200. Moreover, since each portion of the magnetic layer 202 generates heat in response to its temperature, the heat is distributed so that greater heat is supplied to colder areas and less heat is supplied to warmer areas. Thus, heat from the magnetic layer 202 serves to raise the temperature of the length L (see Figure I) to a uniform level. In accordance with the invention as embodied in Figure II, the uniform level substantially corresponds to the AR temperature of the magnetic layer 202 and the temperature at which the desired heat treatment of the length L is effectuated.
  • the AR temperature of the first magnetic layer 202 is selectable to correspond to the tempering temperature or the annealing temperature of the pipe section 100.
  • autoregulation temperatures--near the Curie points-- as high as 1120°C are readily achievable by proper selection of magnetic alloy far the magnetic layer 202.
  • the heat treatment of steel.and other metals (e.g. alloys) from which the pipe section 100 can be made is typically performed at temperatures below the autoregulation upper limits. Accordingly, the proper selection of an alloy wherein AR temperature substantially corresponds to the desired heat treatment temperature can be made.
  • the source 112 may be selectively switched on and off to provide the desired heat treatment period.
  • the heater or heater/article may have plug-or contact elements to which the source 112 can be selectively connected or disconnected as desired.
  • the source 112 is connected to the pipe section 100 and the magnetic layer 110.
  • the pipe section 100 may be a low resistance non-magnetic material.
  • the resistance R thereby drops sharply and little I 2 R heat is produced.
  • a circuit (not shown) may be provided to protect the source 112.
  • the magnetic layer 110 it is noted; has a thickness defined to enable current to spread into pipe section 100 when temperatures rise above the Curie temperature.
  • the magnetic layer is 1.0 to 1.8 skin depths (at the effective permeability) in thickness although other thicknesses may be employed.
  • the source 112 would be connected directly across the magnetic layer.110 which, as desired, may include coupling elements (not shown) for receiving leads from the source 112.
  • pipe section 300 is encircled by a heater 301 that includes a low resistance layer 302 (e.g. copper) which is encircled by magnetic layer 304.
  • the layers 302 and 304 are in contact with each other and are each thermally conductive.
  • An a.c. current is applied to the heater 301, the current being primarily confined to a shallow depth below the AR temperature and the current spreading to'flow along the low resistance path above the AR temperature.
  • the pipe section 300 has heat supplied thereto by the autoregulating heater 301,
  • Figure IV shows the connection of substantially constant a.c. current to an autoregulating heater 400 which is similar to heater 301.
  • a source 402 supplies a.c. current which is initially confined to the outer skin of an outer magnetic layer 404.
  • the inner layer 406 comprises a low resistance, non-magnetic layer 406 which encompasses a solid article 408--such as a pipe, strut, girder, or the like.
  • a.c. current penetrates into the low resistance layer 406 resulting in a decrease in generated heat. That is, as is known in the art, the a.c.
  • the a.c. current flows mainly along the outer surface of layer 404--the surface adjacent the circuit loop--when the temperature is below the AR temperature.
  • the a.c. current spreads through the layer 404, which preferably has. a thickness of several skin depths when the layer 406 is at its effective permeability, and into the layer 406 resulting in less I 2 R heat.
  • a connection of a.c. to the embodiment of Figure II may be made in a manner similar to that shown in Figure aV.
  • the heater of Figure I I may also encircle a solid article--rather than the hollow article shown therein-to achieve the heat treatment thereof.
  • Such heat treatment includes tempering, annealing, strengthening, increasing ductility, relieving stress, or otherwise affecting the metallurgical properties of a metal member.
  • the heat treatment may be effected during assembly, repair or servicing of the metal member to obtain, retain, or regain desired properties.
  • a spring 500 comprises a Beryllium-copper layer 502 and a magnetic alloy layer 504.
  • the Beryllium-copper layer 502 in.a soft and ductile condition may be formed and fit to be placed in a desired location.
  • the magnetic alloy layer 504 has a.c. current supplied thereto by a source 506--which results in the heater 500 initially increasing in temperature.
  • the temperature is regulated at the Curie temperature of the layer 504.
  • the regulated temperature substantially corresponds to the temperature at which the Beryllium-copper layer 502 hardens to a strong, spring-temper condition.
  • This. heat treating is preferably conducted for several minutes at about 400°C.
  • Other alloys, such as ..aluminum and magnesium alloys may also be hardened by such short, low temperature treating. Due to their high inherent conductivity, fabricating such alloys into the heater is contemplated by the invention.
  • alloys may soften if heated too hot or too long. Accordingly, the invention contemplates softening as well in situ.
  • a power cable 600 is terminated at a terminal bus 602 by a clamp ring 604.
  • the ring 604 is initially soft to crimp and conform well to form the termination.
  • the ring 604 comprises a magnetic alloy (see table above) which has an a.c. current applied thereto.
  • the ring 604 autoregulates at the AR temperature thereof and hardens to achieve the desired end-use functionality.
  • the crimp 604 represents both the article to be heat treated and the heater.
  • the invention described therein is not limited to embodiments in which a heater is wrapped around an article in the field.
  • the invention also extends to embodiments wherein the heater and article are incorporated as a single structure. That is, the article to be heated may itself comprise a magnetic material which autoregulates its own temperature.
  • the article may include plural layer embodiments where, for example, a pipe as in Figure I, may include a magnetic layer and a non-magnetic layer concentric and disposed against,the magnetic layer. Such an embodiment operates like the layers 302 and 304 of Figure III.
  • the pipe may comprise two magnetic layers with a non-magnetic layer interposed therebetween.
  • FIG. VII shows a three layer pipe 700 including two concentric magnetic layers 702, 704 with a non-magnetic layer 706 therebetween.
  • a "constant" a.c. source 708 is switchably connectable so that current flows along either the outer surface or inner surface of the pipe 700 when below the AR temperature of layer 702 or of layer 704 respectively.
  • the pipe 700 comprises both the article to be heat treated and the heater disposed to effect the heat treatment.
  • heat treatment may be performed repeatedly as required by simply connecting the a.c. source and applying current to the heater.
  • the invention contemplates heating a metal by any of the various mechanisms discussed above and flushing the heated metal in the field with a gas to effectuate nitriding or carborizing .
  • Carborizing and nitriding are known forms of surface-treating which, in accordance with the invention, are performed in the field, when the article is at the autoregulated temperature.
  • insulation and circuit protection may be included in the various embodiments by one of skill in the art.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Heat Treatment Of Articles (AREA)
  • General Induction Heating (AREA)
  • Control Of Resistance Heating (AREA)
  • Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
  • Processing Of Meat And Fish (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Soft Magnetic Materials (AREA)
EP85301501A 1984-03-06 1985-03-05 Wärmebehandlungsverfahren mittels selbstregulierender Heizvorrichtung Expired - Lifetime EP0156545B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85301501T ATE56476T1 (de) 1984-03-06 1985-03-05 Waermebehandlungsverfahren mittels selbstregulierender heizvorrichtung.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58671984A 1984-03-06 1984-03-06
US586719 1984-03-06

Publications (3)

Publication Number Publication Date
EP0156545A2 true EP0156545A2 (de) 1985-10-02
EP0156545A3 EP0156545A3 (en) 1987-05-13
EP0156545B1 EP0156545B1 (de) 1990-09-12

Family

ID=24346880

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85301501A Expired - Lifetime EP0156545B1 (de) 1984-03-06 1985-03-05 Wärmebehandlungsverfahren mittels selbstregulierender Heizvorrichtung

Country Status (6)

Country Link
EP (1) EP0156545B1 (de)
JP (1) JPH0656793B2 (de)
AT (1) ATE56476T1 (de)
CA (1) CA1265419A (de)
DE (1) DE3579605D1 (de)
WO (1) WO1985004069A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0250094A1 (de) * 1986-06-10 1987-12-23 Metcal Inc. Selbstregulierendes Hochleistungsheizelement
EP0252719B1 (de) * 1986-07-07 1992-11-11 Chisso Engineering CO. LTD. Elektrischer Flüssigkeitserhitzer
WO2012104004A1 (de) * 2011-02-01 2012-08-09 Rwe Technology Gmbh VERFAHREN ZUR WÄRMEBEHANDLUNG VON SCHWEIßNÄHTEN AN KRAFTWERKSBAUTEILEN

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE518744A (de) * 1952-03-28
US4001054A (en) * 1974-04-10 1977-01-04 Makepeace Charles E Process for making metal pipe
US4091813A (en) * 1975-03-14 1978-05-30 Robert F. Shaw Surgical instrument having self-regulated electrical proximity heating of its cutting edge and method of using the same
US4229235A (en) * 1977-10-25 1980-10-21 Hitachi, Ltd. Heat-treating method for pipes
US4256945A (en) * 1979-08-31 1981-03-17 Iris Associates Alternating current electrically resistive heating element having intrinsic temperature control
US4701587A (en) * 1979-08-31 1987-10-20 Metcal, Inc. Shielded heating element having intrinsic temperature control
DE3177193D1 (de) * 1981-03-02 1990-07-19 Metcal Inc Elektrisches widerstandheizelement mit temperaturregelung.

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0250094A1 (de) * 1986-06-10 1987-12-23 Metcal Inc. Selbstregulierendes Hochleistungsheizelement
EP0252719B1 (de) * 1986-07-07 1992-11-11 Chisso Engineering CO. LTD. Elektrischer Flüssigkeitserhitzer
WO2012104004A1 (de) * 2011-02-01 2012-08-09 Rwe Technology Gmbh VERFAHREN ZUR WÄRMEBEHANDLUNG VON SCHWEIßNÄHTEN AN KRAFTWERKSBAUTEILEN

Also Published As

Publication number Publication date
EP0156545A3 (en) 1987-05-13
DE3579605D1 (de) 1990-10-18
JPS61501355A (ja) 1986-07-03
ATE56476T1 (de) 1990-09-15
JPH0656793B2 (ja) 1994-07-27
EP0156545B1 (de) 1990-09-12
CA1265419A (en) 1990-02-06
WO1985004069A1 (en) 1985-09-12

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