U.S. patent application number 11/303694 was filed with the patent office on 2006-06-22 for electric induction impeder.
This patent application is currently assigned to Inductotherm, Corp.. Invention is credited to Oleg S. Fishman, John H. Mortimer, Michael A. Nallen, Paul F. Scott.
Application Number | 20060131299 11/303694 |
Document ID | / |
Family ID | 36602233 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060131299 |
Kind Code |
A1 |
Scott; Paul F. ; et
al. |
June 22, 2006 |
Electric induction impeder
Abstract
An impeder for use in an electric induction welding process is
provided. Optionally the impeder does not require internal forced
cooling. In embodiments using internal forced cooling a high
efficiency cooling system is provided.
Inventors: |
Scott; Paul F.; (Farmington,
CT) ; Nallen; Michael A.; (Old Saybrook, CT) ;
Fishman; Oleg S.; (Maple Glen, PA) ; Mortimer; John
H.; (Little Egg Harbor Township, NJ) |
Correspondence
Address: |
PHILIP O. POST;INDEL, INC.
PO BOX 157
RANCOCAS
NJ
08073
US
|
Assignee: |
Inductotherm, Corp.
|
Family ID: |
36602233 |
Appl. No.: |
11/303694 |
Filed: |
December 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60637590 |
Dec 20, 2004 |
|
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|
Current U.S.
Class: |
219/613 |
Current CPC
Class: |
B23K 2101/06 20180801;
B23K 13/025 20130101 |
Class at
Publication: |
219/613 |
International
Class: |
B23K 13/01 20060101
B23K013/01 |
Claims
1. An impeder for controlling the magnetic field path in an
electric induction welding process, the impeder comprising: a
plurality of magnetically conductive, high Curie temperature solid
wires assembled in a bundle, each of the plurality of wires
electrically isolated from each other; and a high temperature
enclosure surrounding the plurality of wires.
2. The impeder of claim 1 wherein at least one of the magnetically
conductive, high Curie temperature solid wires comprise
permendur.
3. The impeder of claim 1 wherein at least a part of the high
temperature enclosure is formed from sialon.
4. The impeder of claim 1 wherein at least part of the high
temperature enclosure comprises polyaramid polyparaphenylene
terephthalamide.
5. The impeder of claim 1 further comprising: at least one passage
formed through the plurality of wires for flow of a cooling medium
through the at least one passage to cool the plurality of wires; at
least one inlet port disposed in the enclosure for injecting the
cooling medium into the at least one passage; and at least one
outlet port disposed in the enclosure for discharging the cooling
medium from the at least one passage.
6. The impeder of claim 5 further comprising a venturi element at
the inlet of at least one of the at least one inlet port.
7. An impeder for controlling the magnetic field path in an
electric induction welding process, the impeder comprising: a
rolled sheet of magnetically conductive, high Curie temperature
material, the rolled sheet having adjacent surfaces electrically
isolated from each other; and a high temperature enclosure
surrounding the rolled sheet.
8. The impeder of claim 7 further comprising: at least one passage
formed through the rolled sheet for flow of a cooling medium
through the at least one passage to cool the rolled sheet; at least
one inlet port disposed in the enclosure for injecting the cooling
medium into the at least one passage; and at least one outlet port
disposed in the enclosure for discharging the cooling medium from
the at least one passage.
9. An impeder for controlling the magnetic field path in an
electric induction welding process, the impeder comprising: a
magnetic material having at least one entry passage formed
therethrough for entry flow of a cooling medium; and a high
temperature enclosure surrounding the magnetic material, the
magnetic material spaced apart from the interior wall of the
enclosure to form at least one exit passage for exit flow of the
cooling medium, the enclosure having at least one inlet port and at
least one outlet port for injecting the cooling medium into the at
least one entry passage and discharging the cooling medium from the
at least one exit passage, respectively.
10. The impeder of claim 9 wherein the magnetic material comprises
a ferrite material.
11. The impeder of claim 9 wherein the magnetic material comprises
a plurality of magnetically conductive, high Curie temperature
solid wires assembled in a bundle, each of the plurality of wires
electrically isolated from each other.
12. The impeder of claim 9 wherein the magnetic material comprises
a rolled sheet of magnetically conductive, high Curie temperature
material having adjacent surfaces of the rolled sheet electrically
isolated from each other.
13. The impeder of claim 9 further comprising means for directing
the cooling medium from the at least one outlet port to flush
excess mill coolant from the workpiece being welded in the electric
induction welding process.
14. The impeder of claim 9 further comprising a laminar flow
reducing textured surface on the walls of the magnetic material
forming a boundary for the at least one entry and exit
passages.
15. An impeder for controlling the magnetic field path in an
electric induction welding process, the impeder comprising: a
magnetic material; a high temperature enclosure surrounding the
magnetic material, the magnetic material spaced apart from the
interior wall of the enclosure to form a coolant passage around the
exterior of the magnetic material, the enclosure having at least
one inlet port at the first end of the enclosure and at least one
outlet port at the end of the enclosure opposing the first end, the
at least one inlet and outlet ports in communication with the
coolant passage for injecting a cooling medium into the at least
inlet port and discharging the cooling medium from the at least one
outlet port, respectively.
16. The impeder of claim 15 wherein the magnetic material comprises
a ferrite material.
17. The impeder of claim 15 wherein the magnetic material comprises
a plurality of magnetically conductive, high Curie temperature
solid wires are assembled in a bundle, each of the plurality of
wires electrically isolated from each other.
18. The impeder of claim 15 wherein the magnetic material comprises
a rolled sheet of magnetically conductive, high Curie temperature
material having adjacent surfaces of the rolled sheet electrically
isolated from each other.
19. A method of electric induction welding to form a product from a
stock material, the method comprising the steps of: forming an
impeder element from a ferrite, a plurality of electrically
insulated, magnetically conductive, high Curie temperature solid
wires, or a rolled sheet of magnetically conductive, high Curie
Temperature material having adjacent surfaces of the rolled sheet
electrically isolated from each other; surrounding the impeder
element with a high temperature enclosure to form an impeder;
placing the impeder in the vicinity of the weld area for the stock
material; and applying a magnetic field to the weld area to form
the product.
20. The method of claim 19 further comprising the step of forming a
coolant passage between the inner wall of the high temperature
enclosure and the outer boundary of the impeder element in
communication with at least one inlet port and at least one outlet
port in the high temperature enclosure.
21. The method of claim 19 further comprising the step of forming
at least one coolant passage through the impeder element in
communication with at least one inlet port and at least one outlet
port in the high temperature enclosure.
22. The method of claim 21 further comprising the step of forming a
second coolant passage in a space between the inner wall of the
high temperature enclosure and the outer boundary of the impeder
element whereby coolant flowing in the second coolant passage flows
substantially in the opposite direction of coolant flow in the at
least one coolant passage from the at least one inlet port to the
at least one outlet port.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/637,590, filed Dec. 20, 2004, hereby
incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to impeders that can be used
in electric induction welding processes to form, for example, metal
pipe or tubing from strip stock.
BACKGROUND OF THE INVENTION
[0003] Impeders are used in high frequency welded pipe and tube
fabrication processes. They are one or more pieces of ferrite, or
other magnetic material, that is placed inside a pipe or tube
within the weld area. This magnetic material accomplishes two
things. It increases the electrical impedance of the inside current
path of the tube, forcing the current to flow on the vee edges of
the tube instead. It is this current that heats the vee edges prior
to forging them together in the weld box. Secondly, it creates a
low magnetic reluctance path inside the tube between the apex of
the weld vee and the rear of the tube. The lower reluctance path
becomes the preferred path for the magnetic field. Thus more of the
magnetic field generated by the tube welder's induction coil or
contacts passes through the weld vee to utilize this preferred
path, and the welding current induced on the vee edges is thereby
increased. U.S. Pat. No. 4,443,677 further describes the induction
welding process and one type of conventional impeders.
[0004] There are many practical problems encountered with
conventional impeders. The magnetic field that the impeder carries
causes losses in the ferrite due to its finite resistivity and its
coercivity. These losses heat the ferrite, and if heat is not
removed through proper cooling, the ferrite's Curie temperature
(the temperature at which a material looses its magnetic
properties) can be exceeded or the binder that holds the ferrite
material together can disintegrate. Ferrite is a brittle material
and mechanical shock encountered during the tube fabrication
processes can cause it to break into multiple pieces. When this
happens the effective magnetic properties are greatly reduced. The
ferrite is usually enclosed in a jacket generally made from a
fiberglass type material. This helps protect the ferrite from
mechanical shock and provides a means for channeling cooling water
to the ferrite. When fabricating smaller diameter tube, the
diameter of the ferrite must be as large as possible so that the
impeder does not magnetically saturate. This results in tight
clearances between the ferrite and the casing. Thus the cooling
water must not contain contaminants that can plug the coolant
passage between the ferrite and its casing. When this happens, the
ferrite will fail almost immediately due to local over-heating.
Temporary interruptions in the coolant supply can cause steam to
develop inside the impeder casing. When this happens, the ferrite
can temporarily exceed its Curie temperature and this can result in
a section of "cold" or paste weld in the tube.
[0005] One object of the present invention is an impeder that does
not require internal cooling. Another object of the present
invention is to provide an impeder with internal cooling that
operates with improved efficiency.
BRIEF SUMMARY OF THE INVENTION
[0006] In one aspect, the present invention is apparatus for, and
method of, electric induction welding with an impeder. The impeder
is formed from a high temperature impeder element disposed in a
high temperature enclosure. The impeder element may be a plurality
of solid wires formed from permendur, each of which is electrically
isolated from the other wires. The high temperature enclosure may
be formed from a suitable ceramic composition. Internal cooling, if
provided, may be via a closed or open cooling system. In alternate
examples of the invention the impeder element may be a ferrite, or
a rolled magnetically conductive sheet.
[0007] Other aspects of the invention are set forth in this
specification and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing brief summary, as well as the following
detailed description of the invention, is better understood when
read in conjunction with the appended drawings. For the purpose of
illustrating the invention, there is shown in the drawings
exemplary forms of the invention that are presently preferred;
however, the invention is not limited to the specific arrangements
and instrumentalities disclosed in the following appended
drawings:
[0009] FIG. 1(a) is a longitudinal cross sectional view of one
example of an impeder of the present invention that does not
require internal cooling.
[0010] FIG. 1(b) is a cross sectional view of the impeder in FIG.
1(a) along the line A-A.
[0011] FIG. 2(a) is a longitudinal cross sectional view of one
example of an impeder of the present invention with internal
cooling.
[0012] FIG. 2(b) is a cross sectional view of the impeder in FIG.
2(a) along the line B-B.
[0013] FIG. 3(a) is a longitudinal cross sectional view of another
example of an impeder of the present invention with internal
cooling.
[0014] FIG. 3(b) is a cross sectional view of the impeder in FIG.
3(a) along the line C-C.
[0015] FIG. 4(a) is a longitudinal cross sectional view of another
example of an impeder of the present invention with internal
cooling.
[0016] FIG. 4(b) is a cross sectional view of the impeder in FIG.
4(a) along the line D-D.
[0017] FIG. 5 is a cross sectional simplified illustration of an
arrangement for an induction welding process wherein an impeder of
the present invention is used.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Referring now to the drawings, wherein like numerals
indicate like elements, there is shown in FIG. 1(a ) and FIG. 1(b)
a first example of the impeder 10 of the present invention. The
impeder element 12 comprises a bundle of high temperature solid
wires 14 substantially surrounded by a high temperature enclosure
16. In this non-limiting example of the invention the high
temperature solid wires are formed from a suitable type of high
Curie temperature magnetic material, such as but not limited to, a
class of iron-cobalt alloys known as permendur to form a
cylindrical bundle. The term "high Curie temperature" as used
herein generally refers to a Curie temperature of approximately
235.degree. C. or higher. Each wire is electrically isolated from
each of the other wires by means of a suitable insulation that may
be formed by an oxidation process on the surface of each wire, or
by any other suitable method. The term "high temperature enclosure"
as used herein generally refers to an enclosure material capable of
withstanding approximately 200.degree. C., or higher, depending
upon a particular application, and may be formed from a suitable
heat resistant material such as a ceramic composition. One
non-limiting type of ceramic composition that may be used for the
enclosure is a silicon-aluminum-oxynitride composition known as
sialon. Alternatively a synthetic high temperature polymer, such as
a polyaramid polyparaphenylene terephthalamide composition, for
example, in the form of a KEVLAR tape, may be used to form the
enclosure. The enclosure may be cast around the plurality of wires
used in impeder 10. While the impeder in FIG. 1(a) and FIG. 1(b)
has a generally overall cylindrical shape, other shapes are
suitable depending upon a particular application. The term "wire"
as used herein generally refers to a magnetically conductive
material, which may be of any cross sectional shape, and have with
a cross section, typically (but not limited to) between 8 and 24
American Wire Gauge (AWG). Wires of different compositions may be
used in other examples of the inventions, and the enclosure may be
formed from multiple parts of different high temperature
material.
[0019] FIG. 2(a) and FIG. 2(b) illustrate a second example of the
impeder 20 of the present invention. In this example, the impeder
element 22 comprises a cylindrical ring of high temperature solid
wires 24 that is enclosed in a high temperature enclosure 26.
Non-limiting selection of the high temperature solid wires and
enclosure is the same as that described above for the first example
of the invention. Center passage 28 is formed in the cylindrical
ring of wires and provides a flow path for a cooling medium, such
as but not limited to air, water or liquid nitrogen. Flow is from
the INLET to the OUTLET as illustrated by the arrows in FIG. 2(a).
A venturi element 21 can be optionally placed at the inlet of the
center passage to enhance the cooling effect of the cooling medium.
While the impeder 20 in FIG. 2(a) and FIG. 2(b) has a generally
overall cylindrical shape, other shapes are suitable depending upon
a particular application. The ring of high temperature wires, for
example, may be of rectangular shape in cross section with a
suitable passage formed with the plurality of wires for the flow of
a cooling medium. More than one inlet or outlet ports may be
provided depending upon a particular application. In other examples
of the invention more than one passage may be provided through the
impeder element.
[0020] FIG. 3(a) and FIG. 3(b) illustrate a third example of the
impeder 30 of the present invention wherein a closed loop cooling
system is used. In this example, the impeder element 32 comprises a
magnetic material that is enclosed within a high temperature
enclosure 36. The magnetic material is in the shape of an open
cylinder. The magnetic material may be any suitable magnetic
material such as a ferrite or the high temperature wires described
above, and the high temperature enclosure may be a ceramic
composition as described above. Center passage 38 provides a flow
path for a cooling medium through the impeder from the inlet, and
can generally be referred to as a coolant entry passage. More than
one coolant entry passages may be provided in other examples of the
invention. Annular region 39 forms a space between the inner wall
of the enclosure and the magnetic material to provide a flow path
around the impeder to the outlet, and can generally be referred to
as a coolant exit passage. Coolant flow through the impeder is as
illustrated by the arrows in FIG. 3(a). In other examples of the
invention the coolant exit passage may be provided with one or more
passage walls that selectively direct flow around the space between
the inner wall of the enclosure and the magnetic material. More
than one inlet or outlet ports may be provided depending upon a
particular application. As in the second example of the invention a
venturi element can be optionally placed at the inlet to enhance
cooling around the impeder.
[0021] FIG. 4(a) and FIG. 4(b) illustrate a fourth example of the
impeder 40 of the present invention which is similar to the third
example above except that the cooling medium is provided in an open
cooling system wherein the cooling medium enters at the inlet and
flows around impeder element 42 through annular passage 49 to exit
out the outlet as indicated by the arrows in FIG. 4(a). Generally
an open loop system is used when the cooling medium can also serve
as the mill coolant, which is used to wash away oils, oxides,
slivers, and dirt generated during mill processes. Alternatively
the impeder element may be in the shape of an open ring and the
cooling medium will flow through the center passage of the ring.
Impeder element 42 may be any suitable magnetic material such as a
ferrite or the high temperature wires described above, and high
temperature enclosure 46 may be a ceramic composition as described
above.
[0022] In all examples of the invention the impeder element may be
a sheet of high Curie temperature magnetic material, such as but
not limited to permendur, that is rolled to form a generally
cylindrical shape. Adjacent surfaces of the rolled material are
electrically insulated from each other by any suitable method,
including but not limited to an oxidation process. In examples of
the invention wherein the impeder is internally cooled with a
cooling medium, the sheet can be rolled with a bobbin or one or
more removal spindles to form one or more coolant passages within
the impeder element. Suitable but not limiting thickness of the
sheet is in the range of the diameters stated above for the high
temperature wires used in other examples of the invention.
[0023] FIG. 5 illustrates one example of use of an impeder of the
present invention in an electric induction welding process. Stock
material 90, which may be a metal sheet, is driven through weld box
92 in the direction indicated by the arrow to bring opposing edges
of the stock material together. AC current flowing through
induction coil 94, which surrounds the stock material, creates a
magnetic field that couples with the stock material. Induced
currents in the stock material weld the opposing edges of the stock
material together as they pass through the weld box to form a
product 96, such as a tube or pipe. An impeder of the present
invention, for example impeder 10 shown in FIG. 1(a) and FIG. 1(b),
is inserted into the stock material generally in the region shown
in FIG. 5.
[0024] In all examples of the invention wherein a cooling medium is
used, a coolant with a high heat capacity, such as an oil-based
coolant can be used to reduce the flow and pressure requirements
for the cooling system. Using a return flow type impeder casing
design such as that illustrated in FIG. 3(a) and FIG. 3(b) with
pumps at both the inlet and outlet would allow the outlet pressure
to be below atmospheric. Attaching a short hose through a one-way
valve to the outlet side of the impeder would allow the system to
remove any excess mill coolant from inside the welded tube. Excess
mill coolant inside the tube can cause steam blowback through the
weld vee, if it is heated by a subsequent steam annealing process.
Additionally an advanced filtration system can be used to remove
all contaminants from the impeder coolant and thereby eliminate any
cooling passage clogging problem. A refrigeration system can be
used to remove the heat from the coolant and control its inlet
temperature at just below the optimal temperature that maximizes
the magnetic properties of the impeder. By applying a thermally
designed texture to the outside surface of the impeder, the laminar
boundary layer can be eliminated thereby greatly increasing the
heat transfer between the ferrite and the coolant. The term
"thermally designed texture" as used herein refers to any method of
configuring the surface wall or boundary of the magnetic material,
when that wall or boundary is used as a boundary for the cooling
medium passage, to reduce laminar boundary flow conditions from
those existing when the wall or boundary is substantially smooth,
including application of a boundary wall texturing material over
the magnetic material.
[0025] In all examples of the invention an optional inside
cushioning liner can be disposed between the high temperature
enclosure and the impeder to reduce shock transfer to the impeder
material, which can extend the life of the impeder. The inside of
the casing or the liner can be molded with cooling passages and/or
a special texture to create turbulence in the coolant and thereby
increasing the heat transfer between the ferrite and the
coolant.
[0026] If a ferrite is used as the impeder, the ferrite composition
can be optimized for high Curie temperature, and low coercivity and
resistive losses to integrate it with the cooling system and
coolant employed. High temperature binder, possibly ceramic based,
can be used to prevent binder disintegration.
[0027] It is noted that the foregoing examples have been provided
merely for the purpose of explanation and are in no way to be
construed as limiting of the present invention. While the invention
has been described with reference to various embodiments, it is
understood that the words which have been used herein are words of
description and illustration, rather than words of limitations.
Further, although the invention has been described herein with
reference to particular means, materials and embodiments, the
invention is not intended to be limited to the particulars
disclosed herein; rather, the invention extends to all functionally
equivalent structures, methods and uses, such as are within the
scope of the appended claims. Those skilled in the art, having the
benefit of the teachings of this specification, may effect numerous
modifications thereto and changes may be made without departing
from the scope and spirit of the invention in its aspects.
* * * * *