CA1271395A - Annealing of thermally insulated core - Google Patents
Annealing of thermally insulated coreInfo
- Publication number
- CA1271395A CA1271395A CA000514450A CA514450A CA1271395A CA 1271395 A CA1271395 A CA 1271395A CA 000514450 A CA000514450 A CA 000514450A CA 514450 A CA514450 A CA 514450A CA 1271395 A CA1271395 A CA 1271395A
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- Prior art keywords
- core
- annealing
- magnetic core
- temperature
- recited
- 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.)
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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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
-
- 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
Abstract
ABSTRACT
ANNEALING OF THERMALLY INSULATED CORE
A magnetic core is wound from amorphous metal ribbon to form an outside surface, an inside surface and top and bottom surfaces. The core is annealed by being heated to and held at a first temperature for a preselected period of time and then cooled to a second temperature. Insulation applied to the inside and outside surfaces of the core prior to the heating step, substantially reduces the time period required for the anneal and markedly improves the properties of the core.
ANNEALING OF THERMALLY INSULATED CORE
A magnetic core is wound from amorphous metal ribbon to form an outside surface, an inside surface and top and bottom surfaces. The core is annealed by being heated to and held at a first temperature for a preselected period of time and then cooled to a second temperature. Insulation applied to the inside and outside surfaces of the core prior to the heating step, substantially reduces the time period required for the anneal and markedly improves the properties of the core.
Description
1~7~3~3~
ANNEALING OF TH~RMALLY INSULATED CORE
BACKGROUND OF THE INVENTION
This invention relates to an improved process for annealing amorphous metal alloy cores and, more particularly to a process for rapidly heat-treating and magnetically annealing amorphous metal alloy cores that tailors the magnetic properties thereof to specific product applications.
DESCRIPTION OF THE PRIOR ART
Amorphous metal alloys have been developed that evidence magnetic properties superior to conventional crystalline all~oys. These amorphous alloys can be wound to form magnetic cores, approximating a toroid, and are well adapted for use as cores of magnetic devices such as transformers, inductors, electrodeless fluorescent lamps or the like. The adaptation of an amorphous metal core for use in an electrodeless fluorescent lamp is disclosed by U.S. Patent No. 4,227,120 to Luborsky.
Amorphous metal cores have been annealed to enhance the magnetic properties thereof. Typically, the annealing process includes the steps of heat heating the core to a temperature sufficient to achieve stress relief without initiating crystallization and cooling in the presence oi- a magnetic field. Annealing processes of the type described are disclosed by U.S. Patent Nos. 4fll6,728, 4,~49,969, 4,262,233, and 4,298,409.
One of the major problems with conventional annealing processes is the extended time period required to effect the heating step. The problem is particularly troublesome with larger cores. Rapid heating of the core to the annealing temperature produces hot spots at exterior portions thereof, which so degrade the core's magnetis properties that it is rendered unsuitable for use in the aforementioned product applications. To alleviate this problem, the temperature of the core must be elevated to the annealing temperature by a laborious process involving a plurality of graduated heating steps, which is both time consuming and expensive.
~ ~'7~ 5
ANNEALING OF TH~RMALLY INSULATED CORE
BACKGROUND OF THE INVENTION
This invention relates to an improved process for annealing amorphous metal alloy cores and, more particularly to a process for rapidly heat-treating and magnetically annealing amorphous metal alloy cores that tailors the magnetic properties thereof to specific product applications.
DESCRIPTION OF THE PRIOR ART
Amorphous metal alloys have been developed that evidence magnetic properties superior to conventional crystalline all~oys. These amorphous alloys can be wound to form magnetic cores, approximating a toroid, and are well adapted for use as cores of magnetic devices such as transformers, inductors, electrodeless fluorescent lamps or the like. The adaptation of an amorphous metal core for use in an electrodeless fluorescent lamp is disclosed by U.S. Patent No. 4,227,120 to Luborsky.
Amorphous metal cores have been annealed to enhance the magnetic properties thereof. Typically, the annealing process includes the steps of heat heating the core to a temperature sufficient to achieve stress relief without initiating crystallization and cooling in the presence oi- a magnetic field. Annealing processes of the type described are disclosed by U.S. Patent Nos. 4fll6,728, 4,~49,969, 4,262,233, and 4,298,409.
One of the major problems with conventional annealing processes is the extended time period required to effect the heating step. The problem is particularly troublesome with larger cores. Rapid heating of the core to the annealing temperature produces hot spots at exterior portions thereof, which so degrade the core's magnetis properties that it is rendered unsuitable for use in the aforementioned product applications. To alleviate this problem, the temperature of the core must be elevated to the annealing temperature by a laborious process involving a plurality of graduated heating steps, which is both time consuming and expensive.
~ ~'7~ 5
-2-SUMMARY OF THE INVENTION
The present invention provides an improved process for annealing a magnetic core that substantially reduces the time period required for the anneal and markedly improves the magnetic properties thereof. Generally stated, a magnetic core is wound from amorphous metal ribbon to form an outside surface, an inside surface, and top and bottom surfaces. The core is heated to and held at a first temperature for a preselected period of time and then cooled to a second temperature. The improvement comprises the step of insulating the inside and outside surfaces of said core prior to the heating step.
It has been found that by insulating the inside and outside surfaces of the core prior to the heating step substantially larger cores can be annealed in an economical, reliable manner. Heat is transferred rapidly through the top and bottom surfaces along metal paths to interior portions of the core, while the rate of heat transfer to the inside and outside core surfaces is substantially reduced. Inasmuch as the heating step is the rate determining step the overall process time and production costs are minimized. Conventional graduated heating steps are eliminated, with the result that the number of process steps is reduced and the reliability of the annealing process is increased. The core is heated in a highly uniform manner without substantial temperature variations which, if present, would produce mechanical distortions, thermal stresses, and hot spots. Advantageously, magnetic cores produced in accordance ~ith the method of this invention exhibit enhanced magnel:ic properties (ie. AC core loss ranging from about 0.16 to 0.25 W/Kg, exciting power ranging from about 0.25 to 0.45 VA/Kg, and coercive force ranging from about 1.1 to 1.6 A/m at an induction of 1.40 Tesla and a frequency of 60 Hz). Accordingly, magnetic cores annealed in accordance with the present invention are especially well suited for use in Y~:3 inductors, transformers and elec~rodeless flourescent lamps.
BRIEF D~SCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will become apparent when reference is made to the following detailed description and the accompanying drawings in which:
Fig. 1 is a plot showing a time-temperature profile of a magnetic core annealed in accordance with a conventional annealing process; and Fig. 2 is a plot showing a time-temperature profile of a magnetic core annealed in accordance with the annealing process of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Amorphous metal alloys are produced by rapidly quenching molten metals, at a rate of approximately 106C/sec., to develop glassy substances directly in the form of thin ribbons or wires. Typically, the ribbon-thickness ranges from about 20 to 30 ~m and the ribbon width ranges from about 25 to 100 mm. A magnetic core is wound from the amorphous ribbon forming an outside surface, an inside surface, and top and bottom surfaces. The inside surface defines a center aperture extending substantially coaxially with a centroid of the core. In addition, the top and bottom surfaces lie, respectively, in planes substantially perpendicular to cylindrical surfaces formed from the inside and outside surfaces thereof.
The present invention provides an improved process for annealing a magnetic core that substantially reduces the time period required for the anneal and markedly improves the cores magnetic properties, wherein the improvement comprises insulating the inside and outside surfaces of the core before initiating the heating portion of the annealing procedure. The insulation procedure further comprises selecting a thermal insulative substrate having, in combination, a thermal conductivity ranging from about 0.03 to 0.14 W/mC, and 71;3~3t~
. .~ .. ~
linear shrinkage ranging from about 1 to 3 percent up to 500C. It is within the scope of the present invention to employ a preEabricated insulation or one that is manually prepared from component parts and which satisfies the above mentioned criteria. Once selected, the insulation is applied to the inside and outside surfaces by a method selected from the group consisting of wrapping, pain~ing, casting and dipping.
Wrapping of the insulation is readily accomplished using conventional equipment and procedures, and at low cost. According, wrapping is the preferred method for applying the insulation to the core. Typically, the insulation is applied such that the thickness dimension thereof extends radially outward from the outside surface and radially inward from the inside surface of the core and ranges from about 25 to 75mm.
In accordance with the present invention, the magnetic properties of the core can be enhanced by annealing. The process of annealing generally comprises rapidly heating the core to and holding it at a first temperature for a preselected period of time, which is sufficient to relieve the material of all stresses but which is less than that required to initiate crystallization. Preferably, the oven housing the core is initially rapidly heated to a peak oven temperature ranging from 100 to 160C higher than the first temperature of the particular amorphous alloy chosen.
As the core approaches its annealing temperature the oven temperature is lowered to correspond to that o~ the core (see figure # 2). With this procedure, the time required for heat treatment of the core is substantially reduced. The core is then cooled at a cooling rate ranging from about 0.1 to 100C per minute to a second temperature ranging from about 200 to 25C. The first temperature typically ranges from about 325 to 400C and is below the Curie temperature of the particular amorphous alloy chosen, whereas the second temperature is usually ambient temperature. Preferably, at least ~2 ;~ ;3~3 .
the heating step and, most preferably, each of the heating and cooling steps is carried out in the presence of a magnetic field, the direction of which may be either parallel or perpendicular to the core's longitudinal dXiS depending upon its specific product application. Certain alloys, such as those having a composition consisting essentially of a member selected from the group consisting of Co66Fe4Ni1B14Sil5 and Fe76.85Cr2B16.1Si4.gC0,2s can be annealed in the absence of a magnetic field to attain a substantial improvement in the magnetic properties thereof, as hereinbefore described.
The method of construction of a magnetic core is such that a percentage of the gross area is air, which is trapped between the layers of the spirally wound ribbon. Thus, LGROSS AREA-NET CROSS SECTIONAL AREA] x 100 = PERCENT
AIR AREA.
GROSS AREA
It is also well established that metals are excellent conductors of heat while gases are poor conductors of heat. The thermal conductivity values (k) for metal and air, respectively, are 50.2 J5~l m~l (C) 1 and 0.024 J5-1 m~l (C)-l, Consequently, the air trapped between the layers of ribbon of an uninsulated core serves to impede the heat current (H) to the center along the ribbon thickness, wherein H = kA (T~ -dTl) k is the thermal condivity of the material, A is the material's cross-sectional area, T2-Tl is the temperature difference between two points, and d is distance between the two points. As a result of this poor conduction, hot spots develop at exterior portions of the core which so degrade its magnetic properties that it is rendered unsuitable for use in transformers, ~,'3g~-inductors, electrodeless flourescent lamps, or the like. Furthermore, thermal conductivity tests performed on uninsulated sample cores at ~00C reveal that the thermal conductivity through the ribbon width is over 20 times greater than through the ribbon thickness for both the heating and cooling stepsO We have found that by thermally insulating the inside and outside surfaces prior to the heating step while, at the same time, leaving the top and bottom surfaces exposed, substantially larger cores can be annealed in an economical reliable manner. This is because heat is transferred rapidly through the top and bottom surfaces along metal paths to interior portions of the core, while the rate of heat transfer to inside and outside core surfaces is substantially reduced. Inasmuch as the heating step is the rate determining step, the overall process time, and production costs are minimized.
Conventional, graduated heating steps are eliminated, with the result that the number of process steps are reduced and the reliability of the annealing process is increased. The core is heated in a highly uniform manner without substantial temperature variations which, if present, would produce mechanical distortions, thermal stresses, and hot spots. Advantageously, magnetic cores produced in accordance with the method of this invention exhibit enhanced magnetic properties (i.e~ AC core loss ranging from about 0.16 to 0.25 W/Kg, exciting power ranging from about 0.25 to 0.45 VA/Kg, and coercive force ranging from about 1.1 to 1.6 A/m at an induction of 1.40 Tesla and a frequency of ~0 Hz~.
Accordingly, magnetic cores annealed in accordance with the present invention are especially well suited for use in inductors, transformers, and electrodeless flourescent lamps.
The following examples are presented to provide a more complete understanding of the invention. The speci~ic techniques, conditions, materials, ~preparations, and reported data set forth to illustrate ~;~.7~39t~
~ 7--the principles and practice of the invention are exemplary an~ should not be construed as limiting the scope of the invention.
EXA
Toroidal test samples were prepared by spirally winding 100 mm wide alloy ribbon of Metglas~ 2605 S-2, having a nominal composition of Fe78B13Sig, The average inside and outside diameters of the various test samples were 172 mm and 377 mm, respectively, with an average weight of 55 kg. Six turns of high temperature magnetic wire were wound parallel to the longitudinal axis of the core to provide a magnetic field of 800 A/m for annealing purposes. Several samples were annealed without insulation by a conventional process while others were annealed with insulation by the method of the present invention. The samples were placed in an inert gas atmosphere and heated to their respective annealing temperatures with the 800 A/m field applied during the heating and cooling steps. The samples were cooled to 200C at an average rate of 1.5C/min.
The time-temperature profiles for samples annealed by the conventional annealing process and samples annealed by the process of the present invention are plotted in figures 1 and 2, respectively. Thermocouples were strategically placed the center 2 of each core and 5 mm from the outside surface 1 of the core in order to monitor variations in temperature throughoùt the annealing process. AS shown in Figure 1, the temperature at the center 2 of each core annealed by the conven~ional process differs substantially from the temperature at the outside surface 1 thereof. When cores were annealed using the process of the present invention, as shown in Figure 2, the temperature differential between the center 2 and at the outside surface 1 is minimized. As a result, cores exhibiting the time temperature profile shown in Figure 2 can be annealed within a substantially reduced time period to produce markedly improved magnetic properties.
The present invention provides an improved process for annealing a magnetic core that substantially reduces the time period required for the anneal and markedly improves the magnetic properties thereof. Generally stated, a magnetic core is wound from amorphous metal ribbon to form an outside surface, an inside surface, and top and bottom surfaces. The core is heated to and held at a first temperature for a preselected period of time and then cooled to a second temperature. The improvement comprises the step of insulating the inside and outside surfaces of said core prior to the heating step.
It has been found that by insulating the inside and outside surfaces of the core prior to the heating step substantially larger cores can be annealed in an economical, reliable manner. Heat is transferred rapidly through the top and bottom surfaces along metal paths to interior portions of the core, while the rate of heat transfer to the inside and outside core surfaces is substantially reduced. Inasmuch as the heating step is the rate determining step the overall process time and production costs are minimized. Conventional graduated heating steps are eliminated, with the result that the number of process steps is reduced and the reliability of the annealing process is increased. The core is heated in a highly uniform manner without substantial temperature variations which, if present, would produce mechanical distortions, thermal stresses, and hot spots. Advantageously, magnetic cores produced in accordance ~ith the method of this invention exhibit enhanced magnel:ic properties (ie. AC core loss ranging from about 0.16 to 0.25 W/Kg, exciting power ranging from about 0.25 to 0.45 VA/Kg, and coercive force ranging from about 1.1 to 1.6 A/m at an induction of 1.40 Tesla and a frequency of 60 Hz). Accordingly, magnetic cores annealed in accordance with the present invention are especially well suited for use in Y~:3 inductors, transformers and elec~rodeless flourescent lamps.
BRIEF D~SCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will become apparent when reference is made to the following detailed description and the accompanying drawings in which:
Fig. 1 is a plot showing a time-temperature profile of a magnetic core annealed in accordance with a conventional annealing process; and Fig. 2 is a plot showing a time-temperature profile of a magnetic core annealed in accordance with the annealing process of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Amorphous metal alloys are produced by rapidly quenching molten metals, at a rate of approximately 106C/sec., to develop glassy substances directly in the form of thin ribbons or wires. Typically, the ribbon-thickness ranges from about 20 to 30 ~m and the ribbon width ranges from about 25 to 100 mm. A magnetic core is wound from the amorphous ribbon forming an outside surface, an inside surface, and top and bottom surfaces. The inside surface defines a center aperture extending substantially coaxially with a centroid of the core. In addition, the top and bottom surfaces lie, respectively, in planes substantially perpendicular to cylindrical surfaces formed from the inside and outside surfaces thereof.
The present invention provides an improved process for annealing a magnetic core that substantially reduces the time period required for the anneal and markedly improves the cores magnetic properties, wherein the improvement comprises insulating the inside and outside surfaces of the core before initiating the heating portion of the annealing procedure. The insulation procedure further comprises selecting a thermal insulative substrate having, in combination, a thermal conductivity ranging from about 0.03 to 0.14 W/mC, and 71;3~3t~
. .~ .. ~
linear shrinkage ranging from about 1 to 3 percent up to 500C. It is within the scope of the present invention to employ a preEabricated insulation or one that is manually prepared from component parts and which satisfies the above mentioned criteria. Once selected, the insulation is applied to the inside and outside surfaces by a method selected from the group consisting of wrapping, pain~ing, casting and dipping.
Wrapping of the insulation is readily accomplished using conventional equipment and procedures, and at low cost. According, wrapping is the preferred method for applying the insulation to the core. Typically, the insulation is applied such that the thickness dimension thereof extends radially outward from the outside surface and radially inward from the inside surface of the core and ranges from about 25 to 75mm.
In accordance with the present invention, the magnetic properties of the core can be enhanced by annealing. The process of annealing generally comprises rapidly heating the core to and holding it at a first temperature for a preselected period of time, which is sufficient to relieve the material of all stresses but which is less than that required to initiate crystallization. Preferably, the oven housing the core is initially rapidly heated to a peak oven temperature ranging from 100 to 160C higher than the first temperature of the particular amorphous alloy chosen.
As the core approaches its annealing temperature the oven temperature is lowered to correspond to that o~ the core (see figure # 2). With this procedure, the time required for heat treatment of the core is substantially reduced. The core is then cooled at a cooling rate ranging from about 0.1 to 100C per minute to a second temperature ranging from about 200 to 25C. The first temperature typically ranges from about 325 to 400C and is below the Curie temperature of the particular amorphous alloy chosen, whereas the second temperature is usually ambient temperature. Preferably, at least ~2 ;~ ;3~3 .
the heating step and, most preferably, each of the heating and cooling steps is carried out in the presence of a magnetic field, the direction of which may be either parallel or perpendicular to the core's longitudinal dXiS depending upon its specific product application. Certain alloys, such as those having a composition consisting essentially of a member selected from the group consisting of Co66Fe4Ni1B14Sil5 and Fe76.85Cr2B16.1Si4.gC0,2s can be annealed in the absence of a magnetic field to attain a substantial improvement in the magnetic properties thereof, as hereinbefore described.
The method of construction of a magnetic core is such that a percentage of the gross area is air, which is trapped between the layers of the spirally wound ribbon. Thus, LGROSS AREA-NET CROSS SECTIONAL AREA] x 100 = PERCENT
AIR AREA.
GROSS AREA
It is also well established that metals are excellent conductors of heat while gases are poor conductors of heat. The thermal conductivity values (k) for metal and air, respectively, are 50.2 J5~l m~l (C) 1 and 0.024 J5-1 m~l (C)-l, Consequently, the air trapped between the layers of ribbon of an uninsulated core serves to impede the heat current (H) to the center along the ribbon thickness, wherein H = kA (T~ -dTl) k is the thermal condivity of the material, A is the material's cross-sectional area, T2-Tl is the temperature difference between two points, and d is distance between the two points. As a result of this poor conduction, hot spots develop at exterior portions of the core which so degrade its magnetic properties that it is rendered unsuitable for use in transformers, ~,'3g~-inductors, electrodeless flourescent lamps, or the like. Furthermore, thermal conductivity tests performed on uninsulated sample cores at ~00C reveal that the thermal conductivity through the ribbon width is over 20 times greater than through the ribbon thickness for both the heating and cooling stepsO We have found that by thermally insulating the inside and outside surfaces prior to the heating step while, at the same time, leaving the top and bottom surfaces exposed, substantially larger cores can be annealed in an economical reliable manner. This is because heat is transferred rapidly through the top and bottom surfaces along metal paths to interior portions of the core, while the rate of heat transfer to inside and outside core surfaces is substantially reduced. Inasmuch as the heating step is the rate determining step, the overall process time, and production costs are minimized.
Conventional, graduated heating steps are eliminated, with the result that the number of process steps are reduced and the reliability of the annealing process is increased. The core is heated in a highly uniform manner without substantial temperature variations which, if present, would produce mechanical distortions, thermal stresses, and hot spots. Advantageously, magnetic cores produced in accordance with the method of this invention exhibit enhanced magnetic properties (i.e~ AC core loss ranging from about 0.16 to 0.25 W/Kg, exciting power ranging from about 0.25 to 0.45 VA/Kg, and coercive force ranging from about 1.1 to 1.6 A/m at an induction of 1.40 Tesla and a frequency of ~0 Hz~.
Accordingly, magnetic cores annealed in accordance with the present invention are especially well suited for use in inductors, transformers, and electrodeless flourescent lamps.
The following examples are presented to provide a more complete understanding of the invention. The speci~ic techniques, conditions, materials, ~preparations, and reported data set forth to illustrate ~;~.7~39t~
~ 7--the principles and practice of the invention are exemplary an~ should not be construed as limiting the scope of the invention.
EXA
Toroidal test samples were prepared by spirally winding 100 mm wide alloy ribbon of Metglas~ 2605 S-2, having a nominal composition of Fe78B13Sig, The average inside and outside diameters of the various test samples were 172 mm and 377 mm, respectively, with an average weight of 55 kg. Six turns of high temperature magnetic wire were wound parallel to the longitudinal axis of the core to provide a magnetic field of 800 A/m for annealing purposes. Several samples were annealed without insulation by a conventional process while others were annealed with insulation by the method of the present invention. The samples were placed in an inert gas atmosphere and heated to their respective annealing temperatures with the 800 A/m field applied during the heating and cooling steps. The samples were cooled to 200C at an average rate of 1.5C/min.
The time-temperature profiles for samples annealed by the conventional annealing process and samples annealed by the process of the present invention are plotted in figures 1 and 2, respectively. Thermocouples were strategically placed the center 2 of each core and 5 mm from the outside surface 1 of the core in order to monitor variations in temperature throughoùt the annealing process. AS shown in Figure 1, the temperature at the center 2 of each core annealed by the conven~ional process differs substantially from the temperature at the outside surface 1 thereof. When cores were annealed using the process of the present invention, as shown in Figure 2, the temperature differential between the center 2 and at the outside surface 1 is minimized. As a result, cores exhibiting the time temperature profile shown in Figure 2 can be annealed within a substantially reduced time period to produce markedly improved magnetic properties.
3~35 , .~
The magnetic properties i.e. coercive force (Amperes/meter), A.C. core losses (Watts/kilogra~), and exciting power (Volt-ampers/kilogram) of the samples were measured at an induction o~ 1.40 Tesla and a frequency of 60 Hz. The magnetic values for samples subjected to a conventional anneal and for samples annealed by the process of the present invention are shown in tables I and II, respectively.
TABLE I
CONVENTION ANNEAL PROCESS
Example Alloy Core Core # Dimension mm Wt. kg 1 METGLAS~Inside Diameter 17257 2605 S-2Outside Diameter 383 2 METGLAS~Inside Diameter 17256 2605 S-2Outside Diameter 380 Anneal Temp. Total Anneal Coercive 60Hz, 1.4T
C Cycle Time* Force Magnetic Losses _ _ hr_ A/m W/kg VA/kg 355 10 1.8 0.24 0.39 370 10 1.8 0.25 0.3 * Cool to 200C.
39~:.
,.. ~ 9 TABLE II
WITHIN THE SCOPE OF THE INVENTION
CO~ES ANNEALED WITH INSULATION
Example Alloy Core Core # Dimension mm Wt. kg 1 METGLAS~ Indise Diameter 17253 2605 S-2 Outside Diameter 375 2 METGLAS~ Inside Diameter 17254 2605 S-2 Outside Diameter 375 3 METGLAS~ Inside Diameter 17256 2605 S-2 Outside Diameter 37~
The magnetic properties i.e. coercive force (Amperes/meter), A.C. core losses (Watts/kilogra~), and exciting power (Volt-ampers/kilogram) of the samples were measured at an induction o~ 1.40 Tesla and a frequency of 60 Hz. The magnetic values for samples subjected to a conventional anneal and for samples annealed by the process of the present invention are shown in tables I and II, respectively.
TABLE I
CONVENTION ANNEAL PROCESS
Example Alloy Core Core # Dimension mm Wt. kg 1 METGLAS~Inside Diameter 17257 2605 S-2Outside Diameter 383 2 METGLAS~Inside Diameter 17256 2605 S-2Outside Diameter 380 Anneal Temp. Total Anneal Coercive 60Hz, 1.4T
C Cycle Time* Force Magnetic Losses _ _ hr_ A/m W/kg VA/kg 355 10 1.8 0.24 0.39 370 10 1.8 0.25 0.3 * Cool to 200C.
39~:.
,.. ~ 9 TABLE II
WITHIN THE SCOPE OF THE INVENTION
CO~ES ANNEALED WITH INSULATION
Example Alloy Core Core # Dimension mm Wt. kg 1 METGLAS~ Indise Diameter 17253 2605 S-2 Outside Diameter 375 2 METGLAS~ Inside Diameter 17254 2605 S-2 Outside Diameter 375 3 METGLAS~ Inside Diameter 17256 2605 S-2 Outside Diameter 37~
4 METGLAS~ Inside Diameter 17255 2605 S-2 Outside Diameter 378 Anneal Temp. Total Anneal Coercive 60Hz, 1.4T
C Cycle Time* Force Magnetic Losses hr A/m _ W/kgVA/k~
340 6.5 1.4 0.24 0.44 350 6.5 1.1 0.16 0.29 360 6.5 1.3 0.19 0.36 370 6.5 1.6 0.22 0.41 * Cool to 200C.
Three more sample cores were then annealed without insulation, but with rapid heat treatment, and their magnetic values were measured at an induction of 1.40 Tesla and a frequency of 60 Hz. Magnetic properties of these rapidly annealed, uninsulated cores are set forth in Table III.
.;3~3~3 ,....,~
.
TAELE III
OUTSIDE THE SCOPE OF THE INVENTION
CORE9 ANNEALED WITHOtJT INSULATION
Example Alloy Core Core ~ Dimension mmWt. kg 1 METGLAS3 Inside Diameter 172 54 2605 S-2 Outside Diameter 373 2 METGLAS~ Inside Diameter 54 2605 S-2 Outside Diameter 373 3 METGLAS~ Inside Diameter 172 56 2605 S-2 Outisde Diameter 382 Anneal Temp. ~otal Anneal Coercive 60Hz, 1.4T
C Cycle Time*Force Magnetic Losses hr _ A/m W/kg VA/k~
350 6.5 1.9 0.36 0.49 360 6.5 2.1 0.37 0.55 360 6.5 2.2 0.32 0.77 * Cool to 200C.
In contrast to the cores of Table II, the cores of Table III evidenced high coercive forces and high magnetic losses.
Having thus described the invention in rather full detail it will be understood that such detail need not be strictly adhered to but that further changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.
C Cycle Time* Force Magnetic Losses hr A/m _ W/kgVA/k~
340 6.5 1.4 0.24 0.44 350 6.5 1.1 0.16 0.29 360 6.5 1.3 0.19 0.36 370 6.5 1.6 0.22 0.41 * Cool to 200C.
Three more sample cores were then annealed without insulation, but with rapid heat treatment, and their magnetic values were measured at an induction of 1.40 Tesla and a frequency of 60 Hz. Magnetic properties of these rapidly annealed, uninsulated cores are set forth in Table III.
.;3~3~3 ,....,~
.
TAELE III
OUTSIDE THE SCOPE OF THE INVENTION
CORE9 ANNEALED WITHOtJT INSULATION
Example Alloy Core Core ~ Dimension mmWt. kg 1 METGLAS3 Inside Diameter 172 54 2605 S-2 Outside Diameter 373 2 METGLAS~ Inside Diameter 54 2605 S-2 Outside Diameter 373 3 METGLAS~ Inside Diameter 172 56 2605 S-2 Outisde Diameter 382 Anneal Temp. ~otal Anneal Coercive 60Hz, 1.4T
C Cycle Time*Force Magnetic Losses hr _ A/m W/kg VA/k~
350 6.5 1.9 0.36 0.49 360 6.5 2.1 0.37 0.55 360 6.5 2.2 0.32 0.77 * Cool to 200C.
In contrast to the cores of Table II, the cores of Table III evidenced high coercive forces and high magnetic losses.
Having thus described the invention in rather full detail it will be understood that such detail need not be strictly adhered to but that further changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.
Claims (10)
1. A process for annealing a magnetic core comprising amorphous metallic ribbon, said process comprising the steps of:
a) providing a magnetic core of a plurality of layers of amorphous metallic ribbon, said core having an outer surface defined by a major surface of amorphous metallic ribbon, an inner surface defined by a major surface of amorphous metallic ribbon, and top and bottom surfaces defined by minor surfaces of amorphous metallic ribbon;
b) applying thermal insulation to said outer and inner surfaces of said magnetic core and maintaining said top and bottom surfaces in an uninsulated condition, thus forming a partially insulated core;
c) heating said partially insulated core to a first temperature in a first period of time;
d) maintaining said partially insulated core at said first temperature for a second period of time; and e) cooling said partially insulated core to a second temperature.
a) providing a magnetic core of a plurality of layers of amorphous metallic ribbon, said core having an outer surface defined by a major surface of amorphous metallic ribbon, an inner surface defined by a major surface of amorphous metallic ribbon, and top and bottom surfaces defined by minor surfaces of amorphous metallic ribbon;
b) applying thermal insulation to said outer and inner surfaces of said magnetic core and maintaining said top and bottom surfaces in an uninsulated condition, thus forming a partially insulated core;
c) heating said partially insulated core to a first temperature in a first period of time;
d) maintaining said partially insulated core at said first temperature for a second period of time; and e) cooling said partially insulated core to a second temperature.
2. A process for annealing a magnetic core as recited in claim 1, wherein said first temperature and said first period of time are sufficient to achieve stress relief without initiating crystallization.
3. A process for annealing a magnetic core as recited in claim 1, wherein said cooling step is carried out at a cooling rate ranging from about 0.1 to 100°C per minute.
4. A process for annealing a magnetic core as recited in claim 1, wherein said heating and cooling steps are carried out in the presence of a magnetic field and said magnetic field is applied in a direction parallel to the outer surface of said core.
5. A process for annealing a magnetic core as recited in claim 1, wherein said heating and cooling steps are carried out in the presence of a magnetic field and said magnetic field is applied in a direction perpendicular to the outer surface of said core.
6. A process of annealing a magnetic core as recited in claim 1, wherein said first temperature ranges from about 325 to 400°C and is below the Curie temperature of said amorphous metallic ribbon.
7. A process for annealing a magnetic core as recited in claim 1, wherein said second temperature ranges from about 200 to 25°C.
8. A process for annealing magnetic core as recited in claim 1, wherein said inside surface defines a center aperture extending substantially coaxially with a centroid of said core, and said top and bottom surface lie, respectively, in planes substantially perpendicular to cylindrial surfaces formed from said outer and inner surfaces.
9. A process for annealing a magnetic core as recited in claim 1, wherein said insulating step comprises adhering to said inner and outer surfaces a thermally insulative substrate.
10. A process for annealing a magnetic core as recited in claim 9, wherein said insulating step comprises:
a) forming a thermal insulative substrate having, in combination, a thermal conductivity ranging from about 0.03 to 0.14 W/m°C, and linear shrinkage ranging from about 1 to 3 percent up to 500°C;
b) applying said thermal insulative substrate to said inner and outer surfaces;
c) adhering the thermal insulative substrate and that the thickness dimension thereof extends radially outward from the outer surface and radially inward from the inner surface of said core and ranges from about 25 to 75 mm.
a) forming a thermal insulative substrate having, in combination, a thermal conductivity ranging from about 0.03 to 0.14 W/m°C, and linear shrinkage ranging from about 1 to 3 percent up to 500°C;
b) applying said thermal insulative substrate to said inner and outer surfaces;
c) adhering the thermal insulative substrate and that the thickness dimension thereof extends radially outward from the outer surface and radially inward from the inner surface of said core and ranges from about 25 to 75 mm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76408285A | 1985-08-12 | 1985-08-12 | |
| US764,082 | 1985-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1271395A true CA1271395A (en) | 1990-07-10 |
Family
ID=25069631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000514450A Expired CA1271395A (en) | 1985-08-12 | 1986-07-23 | Annealing of thermally insulated core |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6239007A (en) |
| KR (1) | KR910009495B1 (en) |
| CA (1) | CA1271395A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6910724B2 (en) | 2001-09-27 | 2005-06-28 | Newfrey Llc | Footrest plate |
| US7062990B2 (en) | 2001-09-28 | 2006-06-20 | Newfrey Llc | Footrest plate and footrest plate mounting assembly |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE8914T1 (en) * | 1980-12-29 | 1984-08-15 | Allied Corporation | AMORPHOUS METAL ALLOYS WITH IMPROVED AC MAGNETIC PROPERTIES. |
| JPS6140016A (en) * | 1984-07-31 | 1986-02-26 | Toshiba Corp | Manufacture of core |
-
1986
- 1986-07-23 CA CA000514450A patent/CA1271395A/en not_active Expired
- 1986-08-11 KR KR1019860006583A patent/KR910009495B1/en not_active IP Right Cessation
- 1986-08-12 JP JP61189482A patent/JPS6239007A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| KR870002287A (en) | 1987-03-30 |
| KR910009495B1 (en) | 1991-11-19 |
| JPS6239007A (en) | 1987-02-20 |
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