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Title:
SYSTEM AND METHOD FOR MAGNETIC FIELD SHIELDING IN A WELD REGION
Document Type and Number:
WIPO Patent Application WO/2018/072027
Kind Code:
A1
Abstract:
There is provided a system and method for magnetic field shielding in a weld region. A shielding device is positioned adjacent the weld region. The shielding device comprises an elliptic body having formed therein an aperture adapted to receive the welding apparatus. The shielding device is adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region.

Inventors:
LAROUCHE SYLVAIN (CA)
RIVERIN CAROL (CA)
POTVIN CAMIL (CA)
Application Number:
PCT/CA2017/051247
Publication Date:
April 26, 2018
Filing Date:
October 19, 2017
Export Citation:
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Assignee:
RIO TINTO ALCAN INT LTD (CA)
International Classes:
B23K9/29; B23K9/02; B23K9/26; B23K9/32
Foreign References:
US3458682A1969-07-29
EP0006720A11980-01-09
Attorney, Agent or Firm:
NORTON ROSE FULBRIGHT CANADA LLP, S.E.N.C.R.L., S.R.L. (CA)
Download PDF:
Claims:
CLAIMS:

1 . An arc welding system comprising:

a welding apparatus configured to be displaced along a welding path in a weld region and to perform an arc weld along the welding path; and

a shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region.

2. The system of claim 1 , further comprising a support member configured to support the welding apparatus and the shielding device thereon and to position the welding apparatus and the shielding device adjacent a surface onto which the arc weld is to be performed.

3. The system of claim 1 or 2, wherein the welding apparatus is configured to be displaced along a non-longitudinal welding path.

4. The system of claim 2, wherein the welding apparatus is configured to be displaced along a longitudinal welding path and further wherein the support member comprises: a stationary guiding rail extending along an axis substantially parallel to the longitudinal welding path; and

a frame releasably attached to the guiding rail and configured for linear movement relative thereto along the axis, the frame configured to support the welding apparatus and the shielding device thereon.

5. The system of any one of claims 1 to 4, wherein the shielding device is configured to enclose the weld region and is made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

6. The system of any one of claims 1 to 5, wherein the welding apparatus is centered within the aperture.

7. The system of any one of claims 1 to 5, wherein the welding apparatus abuts against an inner surface of the body.

8. The system of any one of claims 1 to 7, wherein the aperture is shaped as an ellipse having major axis is aligned with a minor axis of the body and a minor axis is aligned with a major axis of the body.

9. The system of claim 8, wherein the major axis of the body is substantially parallel to the welding path.

10. The system of claim 8, wherein the major axis of the body is at a non-zero angle to the welding path.

1 1 . The system of claim 8, wherein the major axis of the body is substantially perpendicular to the welding path.

12. The system of any one of claims 1 to 1 1 , wherein a bottom surface of the body is tapered to enhance visibility of and access to the weld region.

13. The system of any one of claim 1 to 12, wherein the body comprises a plurality of concentric shielding members separated by a gap filled with ambient atmosphere.

14. The system of any one of claim 1 to 12, wherein the body comprises a plurality of concentric shielding members separated by a gap filled with a non-magnetic material.

15. The system of any one of claim 1 to 12, wherein the body comprises a plurality of concentric grooves defining a plurality of shielding members.

16. The system of any one of claims 2 to 15, further comprising at least one actuatable attachment member operatively connecting the shielding device to the support member, the at least one attachment member configured to be actuated for adjusting at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface and accordingly varying at least one of a magnitude and a polarity of the nulling magnetic field.

17. The system of any one of claims 1 to 16, further comprising a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field for determining a position of the shielding device that achieves a desired level of attenuation of the ambient magnetic field.

18. A method for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the method comprising:

positioning a shielding device adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region;

acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path;

comparing the measured ambient magnetic field to a threshold; and

responsive to determining that the measured ambient magnetic field is not within the threshold, causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

19. The method of claim 18, wherein positioning the shielding device adjacent the weld region comprises positioning the shielding device with the weld region enclosed therein, the shielding device made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

20. The method of claim 18 or 19, wherein positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body substantially parallel to the welding path.

21 . The method of claim 18 or 19, wherein positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body at a non-zero angle to the welding path.

22. The method of claim 18 or 19, wherein positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body substantially perpendicular to the welding path.

23. The method of any one of claims 18 to 22, wherein positioning the shielding device adjacent the weld region comprises operatively connecting the shielding device to a support member via at least one actuatable attachment member, the support member configured to support the shielding device thereon and to position the shielding device adjacent a surface onto which the arc weld is to be performed, and further wherein causing a position of the shielding device to be adjusted comprises actuating the attachment member to enable adjustment of at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface.

24. The method of any one of claims 18 to 23, wherein the measurement of the ambient magnetic field is acquired from a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

25. A system for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the system comprising:

a memory;

a processor; and

at least one application stored in the memory and executable by the processor for: outputting a first control signal comprising instructions for causing a shielding device to be positioned adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region;

acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path;

comparing the measured ambient magnetic field to a threshold; and responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

26. The system of claim 25, wherein the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with the weld region enclosed therein, the shielding device made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

27. The system of claim 25 or 26, wherein the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body substantially parallel to the welding path.

28. The system of claim 25 or 26, wherein the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body at a non-zero angle to the welding path.

29. The system of claim 25 or 26, wherein the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body substantially perpendicular to the welding path.

30. The system of any one of claims 25 to 29, wherein the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising operatively connecting the shielding device to a support member via at least one actuatable attachment member, the support member configured to support the shielding device thereon and to position the shielding device adjacent a surface onto which the arc weld is to be performed, and for causing a position of the shielding device to be adjusted comprises actuating the attachment member to enable adjustment of at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface.

31 . The system of any one of claims 25 to 30, wherein the at least one application is executable by the processor for acquiring the measurement of the ambient magnetic field from a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

32. A computer readable medium having stored thereon program code executable by a processor for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the program code executable for:

outputting a first control signal comprising instructions for causing a shielding device to be positioned adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region;

acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path;

comparing the measured ambient magnetic field to a threshold; and

responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

Description:
SYSTEM AND METHOD FOR MAGNETIC FIELD SHIELDING IN A WELD REGION

[0001 ] The present application claims the benefit of United States Provisional Patent Application No. 62/410,614 filed on October 20, 2016, the contents of which are hereby incorporated in their entirety by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to systems and methods for controlling the magnetic field in a weld region where high ambient magnetic fields are present.

BACKGROUND OF THE ART

[0003] Industrial processes used to extract metals, such as aluminum welding, typically employ large currents, which cause local magnetic fields greater than 50 Gauss. However, the high ambient magnetic field environment affects electric arcs that result from such welding operations, leading to arc instability and low quality welds. Welding repair work is therefore frequently required, which causes increased costs and reduced efficiency.

[0004] Several methods have been proposed to overcome the known challenge of arc instability in high ambient magnetic field welding environments. One method involves positioning a torus around the welding head in order to lower the ambient magnetic field and stabilize the electric arc at the weld position. However, this method leads to unsatisfactory results due to broken and low quality welds, which in turn decreases the overall efficiency of the welding process and causes energy losses for the plant. Other proposed systems and methods require bulky and expensive hardware components to achieve arc stability, thus proving time consuming, cumbersome, and unsuitable for use on the field.

[0005] There is therefore a need to address the problem of arc instability during welding operations.

SUMMARY

[0006] The present disclosure describes the use of a magnetic field shielding device for controlling magnetic fields, and accordingly weld arcs, during welding operations performed in high magnetic field environments (e.g. greater than 50 Gauss). The shielding device creates a low magnetic field zone in the weld region, thereby improving the quality of resulting welds. [0007] In accordance with a first broad aspect, there is provided an arc welding system comprising a welding apparatus configured to be displaced along a welding path in a weld region and to perform an arc weld along the welding path and a shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region.

[0008] In some embodiments, the system further comprises a support member configured to support the welding apparatus and the shielding device thereon and to position the welding apparatus and the shielding device adjacent a surface onto which the arc weld is to be performed.

[0009] In some embodiments, the welding apparatus is configured to be displaced along a non-longitudinal welding path.

[0010] In some embodiments, the welding apparatus is configured to be displaced along a longitudinal welding path and the support member comprises a stationary guiding rail extending along an axis substantially parallel to the longitudinal welding path, and a frame releasably attached to the guiding rail and configured for linear movement relative thereto along the axis, the frame configured to support the welding apparatus and the shielding device thereon.

[001 1 ] In some embodiments, the shielding device is configured to enclose the weld region and is made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

[0012] In some embodiments, the welding apparatus is centered within the aperture.

[0013] In some embodiments, the welding apparatus abuts against an inner surface of the body.

[0014] In some embodiments, the aperture is shaped as an ellipse having major axis is aligned with a minor axis of the body and a minor axis is aligned with a major axis of the body. [0015] In some embodiments, the major axis of the body is substantially parallel to the welding path.

[0016] In some embodiments, the major axis of the body is at a non-zero angle to the welding path.

[0017] In some embodiments, the major axis of the body is substantially perpendicular to the welding path.

[0018] In some embodiments, a bottom surface of the body is tapered to enhance visibility of and access to the weld region.

[0019] In some embodiments, the body comprises a plurality of concentric shielding members separated by a gap filled with ambient atmosphere.

[0020] In some embodiments, the body comprises a plurality of concentric shielding members separated by a gap filled with a non-magnetic material.

[0021 ] In some embodiments, the body comprises a plurality of concentric grooves defining a plurality of shielding members.

[0022] In some embodiments, the system further comprises at least one actuatable attachment member operatively connecting the shielding device to the support member, the at least one attachment member configured to be actuated for adjusting at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface and accordingly varying at least one of a magnitude and a polarity of the nulling magnetic field.

[0023] In some embodiments, the system further comprises a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field for determining a position of the shielding device that achieves a desired level of attenuation of the ambient magnetic field.

[0024] In accordance with a second broad aspect, there is provided a method for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the method comprising positioning a shielding device adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region, acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path, comparing the measured ambient magnetic field to a threshold, and, responsive to determining that the measured ambient magnetic field is not within the threshold, causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

[0025] In some embodiments, positioning the shielding device adjacent the weld region comprises positioning the shielding device with the weld region enclosed therein, the shielding device made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

[0026] In some embodiments, positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body substantially parallel to the welding path.

[0027] In some embodiments, positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body at a non-zero angle to the welding path.

[0028] In some embodiments, positioning the shielding device adjacent the weld region comprises positioning the shielding device with a major axis of the body substantially perpendicular to the welding path.

[0029] In some embodiments, positioning the shielding device adjacent the weld region comprises operatively connecting the shielding device to a support member via at least one actuatable attachment member, the support member configured to support the shielding device thereon and to position the shielding device adjacent a surface onto which the arc weld is to be performed, and causing a position of the shielding device to be adjusted comprises actuating the attachment member to enable adjustment of at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface.

[0030] In some embodiments, the measurement of the ambient magnetic field is acquired from a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

[0031 ] In accordance with a third broad aspect, there is provided a system for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the system comprising a memory, a processor, and at least one application stored in the memory and executable by the processor for outputting a first control signal comprising instructions for causing a shielding device to be positioned adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region, acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path, comparing the measured ambient magnetic field to a threshold, and responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

[0032] In some embodiments, the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with the weld region enclosed therein, the shielding device made of a high magnetic field permeability material configured to draw the ambient magnetic field into itself, thereby shielding the weld region.

[0033] In some embodiments, the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body substantially parallel to the welding path.

[0034] In some embodiments, the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body at a non-zero angle to the welding path. [0035] In some embodiments, the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising positioning the shielding device with a major axis of the body substantially perpendicular to the welding path.

[0036] In some embodiments, the at least one application is executable by the processor for positioning the shielding device adjacent the weld region comprising operatively connecting the shielding device to a support member via at least one actuatable attachment member, the support member configured to support the shielding device thereon and to position the shielding device adjacent a surface onto which the arc weld is to be performed, and for causing a position of the shielding device to be adjusted comprises actuating the attachment member to enable adjustment of at least one of an angular position and an axial position of the shielding device relative to the support member and to the surface.

[0037] In some embodiments, the at least one application is executable by the processor for acquiring the measurement of the ambient magnetic field from a sensing device adapted to be received in the aperture in place of the welding apparatus prior to the arc weld being performed and configured for displacement along the welding path, the sensing device configured to measure a direction and a magnitude of the ambient magnetic field.

[0038] In accordance with a fourth broad aspect, there is provided a computer readable medium having stored thereon program code executable by a processor for magnetic field shielding in a weld region where an arc weld is to be performed along a welding path using a welding apparatus, the program code executable for outputting a first control signal comprising instructions for causing a shielding device to be positioned adjacent the weld region, the shielding device comprising an elliptic body having formed therein an aperture adapted to receive the welding apparatus, the shielding device adapted for movement along the welding path and configured to generate a nulling magnetic field that opposes an ambient magnetic field present in the weld region, acquiring a measurement of the ambient magnetic field as the shielding device is displaced along the welding path, comparing the measured ambient magnetic field to a threshold, and responsive to determining that the measured ambient magnetic field is not within the threshold, outputting a second control signal comprising instructions for causing a position of the shielding device to be adjusted to bring the measured ambient magnetic field within the threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0040] Figure 1 is a schematic perspective view of a system for magnetic field shielding in a weld region where high magnetic fields are present, in accordance with a first illustrative embodiment;

[0041 ] Figure 2 is a schematic perspective view of a shielding device, in accordance with a first illustrative embodiment;

[0042] Figure 3 shows a schematic perspective view, a front view, and a top view of a shielding device, in accordance with a second illustrative embodiment;

[0043] Figure 4A and Figure 4B illustrate the magnitude of the magnetic field in the longitudinal plane of the shielding device, in accordance with an illustrative embodiment;

[0044] Figure 5 is a schematic perspective view of a system for magnetic field shielding in a weld region where high magnetic fields are present, in accordance with a second illustrative embodiment;

[0045] Figure 6 is a schematic perspective view of a measuring device, in accordance with an illustrative embodiment;

[0046] Figure 7 is a flowchart of a method for magnetic field shielding in a weld region where high ambient magnetic fields are present, in accordance with an illustrative embodiment; and

[0047] Figure 8 is a block diagram of a control system for magnetic field shielding in a weld region where high ambient magnetic fields are present, in accordance with an illustrative embodiment. [0048] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION

[0049] Referring to Figure 1 , a system 100 for magnetic field shielding in a weld region where high ambient magnetic fields are present will now be described. The system 100 may be used for controlling electric arcs produced when performing welding operations on a workpiece 102. In one embodiment, the system 100 is used in aluminum arc welding (e.g. smelting) processes, such as Metal Inert Gas (MIG) welding processes, Tungsten Inert Gas (TIG) welding processes, or the like. The proposed system 100 may be used to perform welding on planar surfaces. As such, applications for the system 100 include, but are not limited to, end-to-end welding and overlapping welding. In particular, the system 100 is illustratively used to consolidate bolted joints on positive current input members of electrolytic cells. As understood by those skilled in the art, when welding positive current input members, the direction and magnitude of the local ambient magnetic field varies over the entire length of the weld bead (i.e. along the weld path A). As will be discussed further below, using the system 100 allows to reduce the local ambient magnetic field so that welding can be reliably performed.

[0050] In the illustrated embodiment, the workpiece 102 is an elongate and substantially planar piece of aluminum that is welded along a welding path or direction A, which is substantially parallel to the x-axis. As such, longitudinal arc welds (not shown) can be obtained. It should however be understood that the system 100 may be used for other welding applications and that non-longitudinal arc welds may be performed. In this case, the system 100 may be used to weld the workpiece 102 along a non-longitudinal path. It should also be understood that although the workpiece 102 is illustrated as being a substantially planar elongate piece of material, other shapes may apply. Moreover, although the workpiece 102 is illustrated herein as being formed of a single piece of material, the workpiece 102 may comprise two separate pieces of material having abutted edges that define a joint to be welded. Different arc welding positions may also apply. For example, the weld bead may be vertical (i.e. extend along the z-axis) or horizontal (i.e. extend along the x-axis, as illustrated) and the welding direction A may accordingly extend along the z-axis or the x-axis (as illustrated). It should also be understood that the arc welding position may be flat or overhead. [0051 ] The system 100 illustratively comprises a guiding rail 104, which is configured to be positioned (e.g. using suitable support means and attachment means, such as screws, nuts, and bolts, not shown) adjacent the workpiece 102 to be welded, at a distance that facilitates the welding operation. In one embodiment, the guiding rail 104 is attached to a conductor of an electrolytic cell positive current input member (i.e. a current-carrying conductor). The guiding rail 104 extends along a longitudinal axis B, which is substantially parallel to the welding direction A. A support member 106 is releasably attached to the rail 104 and adapted for linear movement relative to the rail 104, along the axis B. For this purpose, a linear movement mechanism (not shown), such as a linear bearing mechanism, or the like may be used. A motor (not shown) or other suitable driving means may be provided to cause steady axial displacement of the support member 106 relative to the guiding rail 104. In some embodiments, the welder may also manually displace the support member 106. It should be understood that any suitable mechanism enabling sliding movement of the support member 106 relative to the rail 104 may be used.

[0052] A magnetic field shielding device 108 is illustratively attached (using suitable attachment means as in 1 10 1 and 1 10 2 , such as screws, bolts, nuts, and the like) to the support member 106 and extends away therefrom towards the workpiece 102. In one embodiment, the shielding device 108 contacts an exposed surface (not shown) of the workpiece 102, thereby engaging the latter. Other embodiments may apply but it should be understood that it is desirable for the shielding device 108 to be positioned as close as possible to the workpiece 102. The shielding device 108 is thus adapted for axial movement in the welding direction A, along the weld bead (not shown) to be achieved.

[0053] The shielding device 108 is illustratively made of a high magnetic field permeability material, such as mild steel or any other suitable material, and serves to enclose and shield the weld region (not shown). In particular, the shielding device 108 draws into itself the local ambient magnetic field that is typically generated in a loop around the positive current input member conductor (also referred to as the current-carrying conductor). The local ambient magnetic field can therefore be countered and as such significantly reduced. A low magnetic field zone is therefore created at the weld region, i.e. adjacent the electric arc (generated by a welding head 1 12 once the welding operation proceeds) and the molten weld pool (none shown). Welding can therefore be facilitated and high quality (e.g. in terms of uniformity, porosity) welds obtained. Broken welds, and accordingly energy losses, can be reduced, thereby improving efficiency of the welding process.

[0054] The local ambient magnetic field may be reduced to a predetermined threshold, the threshold value being selected such that the local ambient magnetic field is sufficiently attenuated to stabilize the electric arc and facilitate welding. In environments where magnetic fields having magnitudes up to 750 Gauss and varying directions (up to about 45 degrees) are present, using the shielding device 108 allows to achieve a magnetic field attenuation of up to eighteen (18) times the local ambient magnetic field. In other words, a magnetic field threshold value below 50 Gauss (e.g. of about 40 Gauss) can be reached in such environments. It should be understood that other magnetic field attenuation levels may apply.

[0055] Still referring to Figure 1 , the attachment means 1 10i may be configured for rotation about a rotary axis C1 and the attachment means 1 10 2 may be configured for rotation about a rotary axis C2. In this manner, the coupling between the shielding device 108 and to the support member 106 may be adjusted (e.g. tightened or released) to ensure accurate positioning of the shielding device 108 relative to the weld region. Once the desired position has been achieved, the attachment means 1 10i , 1 10 2 may then be used to lock the shielding device 108 in place. In one embodiment, actuation of the attachment means 1 10 1 (e.g. rotation about axis C1 ) enables rotary movement of the shielding device 108 about the x-axis. Actuation of the attachment means 1 10 2 (e.g. rotation about axis C2) may further enable rotary movement of the shielding device 108 about the y-axis. This in turn allows to adjust the angular position of (i.e. tilt) the shielding device 108 relative to a surface (e.g. a plane, not shown) of the workpiece 102. In another embodiment, actuation of the attachment means 1 10 2 enables axial movement of the shielding device 108 about the z-axis in order to adjust the vertical position of the shielding device 108. In particular, the shielding device 108 may be positioned closer to or further away from the exposed workpiece surface. Other embodiments may apply. It should also be understood that, in some embodiments, a single attachment means 1 10i or 1 10 2 may be provided. In this case, it may be desirable for actuation of the attachment means 1 10 1 or 1 10 2 to cause axial displacement of the shielding device 108 about the z-axis in order to enhance the resulting shielding effect. [0056] The position (e.g. axial positioning) and orientation (e.g. angular positioning) of the shielding device 108 may be adjusted in accordance with the welding application (e.g. the type of weld bead) to be performed and according to the level of magnetic field attenuation to be achieved. In particular, the position and orientation of the shielding device 108 illustratively depends on the angle between the ambient magnetic field (i.e. the angle of the magnetic field vector component) and the weld bead, as well as on the constraints of the weld bead (e.g. end-to-end or overlapping weld bead). It may also be desirable to position and orient the shielding device 108 so as to ensure access to the weld region and provide adequate ergonomics for the welder. In some embodiments, the shielding device 108 is positioned so as to extend along a plane (not shown) that is substantially parallel to an exposed surface (not shown) of the workpiece 102. It should be understood that, in other embodiments and depending on the direction of the ambient magnetic field, the shielding device 108 may be positioned so as to extend along a plane that is at a different angle (e.g. ten (10) degrees, thirty (30) degrees, or the like) to the exposed surface of the workpiece.

[0057] Figure 2 illustrates a shielding device 200 in accordance with a first embodiment. The shielding device 200 comprises a substantially planar elliptic member 202 having a major axis D1 and a minor axis D2. A bottom surface (not shown) of the elliptic member 202 is illustratively tapered to enhance visibility of and access to the weld region (e.g. for the welder). An elongate aperture 204 having an inner surface 206 is formed about a center of the elliptic member 202, the aperture 204 being shaped as an ellipse whose major axis (not shown) is aligned with the minor axis D2 and whose minor axis (not shown) is aligned with the major axis D1 .

[0058] Figure 3 illustrates a shielding device 300 according to a second embodiment. The shielding device 300 comprises a substantially planar elliptic member 302 having a major axis E1 and a minor axis E2. A bottom surface (not shown) of the elliptic member 302 is illustratively tapered to enhance visibility and access for the welder. An elongate aperture 304 having an inner surface 306 is formed about a center of the elliptic member 302, the aperture 304 being shaped as an ellipse whose major axis (not shown) is aligned with the minor axis E2 and whose minor axis (not shown) is aligned with the major axis E1 . The shielding device 200 or 300 draws the local ambient magnetic field into itself (as discussed above) such that a low magnetic field zone is created at the aperture 204 or 304 to facilitate welding.

[0059] The illustrated elliptic member 302 comprises three (3) concentric elliptic shielding portions (or members) 308a, 308b, and 308c positioned adjacent to one another. Adjacent shielding portions 308a, 308b, and 308c are separated by a channel, with shielding portions 308a and 308b being separated by channel 310a and shielding portions 308b and 308c being separated by channel 310b. In one embodiment, each channel 310a, 310b is a gap (as illustrated) that extends from a top surface (not shown) to a bottom surface (not shown) of the elliptic member 302. The channels 310a and 310b may be voids filled with the ambient atmosphere. It should however be understood that a non-magnetic material may be provided in each channel 310a, 310b in order to space apart the adjacent shielding portions 308a, 308b, and 308c. Suitable attachment means (not shown) may be used to hold the elliptic shielding portions 308a, 308b, and 308c together. In another embodiment, each channel is a groove (not shown) formed in the elliptic member 302 (e.g. on the upper surface thereof) to delineate the shielding portions 308a, 308b, and 308c. Provision of the channels 310a and 310b causes the shielding device 300 to generate a more uniform counterbalancing magnetic field, thereby enhancing the resulting shielding effect and improving control over the behaviour of the electric arc along the weld path A. The location of the channels 310a and 310b on the elliptic member 302 may therefore be selected so as to achieve optimal magnetic field attenuation.

[0060] It should also be understood that, according to the welding application, the geometry, dimensions, and overall configuration of the shielding device 200 or 300 may be adjusted so as to achieve optimal magnetic field attenuation. As such, although elliptic shielding devices (as in 200, 300) are described and illustrated herein, other shapes (e.g. rectangular) may apply. It should also be understood that the shielding device may comprise one or more shielding portions, the number of shielding portions being selected to achieve the desired level of magnetic field attenuation. In addition, the location of the channels (as in 310a and 310b in Figure 3) may be varied to achieve a desired level of magnetic field attenuation. The shielding device's dimensions may also vary. It has been found that the elliptic shielding device 300 illustrated in Figure 3 allows to reduce the ambient magnetic field to about 40 Gauss. The elliptic member 302 of Figure 3 has a dimension d1 of 6.25 inches along the major axis E1 , a dimension d2 of 5 inches along the minor axis E2, a thickness d3 of 0.0625 inches, and an aperture 304 of dimensions d4 of 1 .5 inches along the major axis E1 and d5 of 2.5 inches along the minor axis E2.

[0061 ] Still referring to Figure 2 and Figure 3, the aperture 204 or 304 of the elliptic member 202 or 302 is adapted to receive a welding head (reference 1 12 in Figure 1 ) therein, such that welding is performed in the aperture 204 or 304, in the low magnetic field zone created thereat. The welding head 1 12 is illustratively positioned so as to abut against the inner surface 206 or 306 that defines the aperture 204 or 304 formed in the shielding device 200 or 300. Depending on the welding operation to be performed, the welding head 1 12 may be positioned in the aperture 204 or 304 so as to abut against either a leftmost part or a rightmost part of the inner surface 206 or 306. In other embodiments, the welding head 1 12 is centered in the aperture 204 or 304. Still, it should be understood that centering of the welding head 1 12 in the aperture 204 or 304 may decrease the level of magnetic field attenuation achieved by the shielding device 200 or 300. The positioning of the welding head 1 12 in the aperture 204 or 304 may indeed affect the magnetic field attenuation that is achieved. This is illustrated in Figure 4A and Figure 4B. It can be seen that the positioning of a welding head 402 in the aperture (not shown) of a shielding device 404 is correlated with the angle of the magnetic field relative to the weld bead (not shown). For example and as shown in Figure 4A, when the shielding device 404 is tilted by a first angle φ 1 relative to the exposed surface 406 of the conductor 408, the magnetic field has a vector component 410a that is at an angle θ 1 relative to the exposed surface 406. The welding head 402 is then positioned in the shielding device 404 so as to abut against the rightmost part of the aperture (not shown) and extend along a direction that is substantially parallel to the direction of the vector component 410a. As shown in Figure 4B, when the shielding device 404 is tilted by a second angle φ 2 relative to the exposed surface 406 of the conductor 408, the magnetic field has a vector component 410b that is at an angle θ 2 relative to the exposed surface 406. The welding head 402 is then positioned in the shielding device 404 so as to abut against the leftmost part of the aperture (not shown) and extend along a direction that is substantially parallel to the direction of the vector component 410b.

[0062] According to the welding application at hand, the shielding device's position may also be such that the shielding device's major axis is at an angle (e.g. substantially parallel or substantially perpendicular) to the welding direction A and to the axis B of the guiding rail (reference 104 in Figure 1). In the embodiment of Figure 1 , the shielding device 108 is secured to the support member 106 such that the major axis E of the shielding device 108 is substantially parallel (e.g. at an angle of zero degrees) to the axis B and to the welding direction A. In this manner, it is possible to perform welds, which are longitudinal to a direction along which the current-carrying conductor (not shown) extends. Figure 5 illustrates an alternative embodiment in which a magnetic field control system 500 is provided comprising a shielding device 502 that is secured to a guiding rail 504 such that the major axis F of the shielding device 502 is substantially perpendicular (e.g. at an angle of ninety (90) degrees) to the axis B and to the welding direction A. In this manner, it is possible to perform welds, which are transverse to a direction along which the current- carrying conductor (not shown) extends. It should however be understood that the shielding device's major axis may be at an angle to the welding direction A and to the axis B other than the angles (e.g. zero and ninety (90) degrees) illustrated in Figure 1 and Figure 5. For example, the shielding device's major axis may be positioned at an angle of forty-five (45) degrees relative to the welding direction A and the axis B. Other embodiments may apply.

[0063] Referring back to Figure 1 , prior to the welding head 1 12 being used to weld the workpiece 102, a sensing device (e.g. a probe) 1 14 is illustratively used in cooperation with the shielding device 108 to determine the shielding device's zone of maximum magnetic field attenuation. In particular, the sensing probe 1 14 may be used to measure the local ambient magnetic field at the weld region (i.e. the magnetic field that will affect the electric arc generated by the welding head 1 12 once the welding operation proceeds) and accordingly determine the position of the shielding device 108 that will suitably cancel the local magnetic field. Once the desired position of the shielding device 108 has been determined, the welding head 1 12 may be positioned adjacent the weld region and the welding operation may proceed.

[0064] The sensing probe 1 14 may be received in the aperture 1 16 formed in the shielding device 108 and secured to the guiding rail 104 using a suitable attachment means (not shown). In one embodiment, a tip (not shown) of the sensing probe 1 14 extends away from the guiding rail 104 and towards the workpiece 102 by a predetermined distance that is selected such that the electric arc, which is generated during the welding operation, is created at a the given distance from the guiding rail 104. [0065] The sensing probe 1 14 illustratively comprises a semiconductor device (not shown), which is responsive to local magnetic fields that arise in the vicinity of the weld region. Upon detecting the local magnetic field, the semiconductor device outputs an electrical voltage, which is proportional to the strength and polarity of the local magnetic field. The output voltage is then detected by a suitable measuring device (not shown) as the sensing probe 1 14 passes along the weld bead and a corresponding reading of the magnitude and direction of the local magnetic field is produced. In one embodiment, the semiconductor device is a three-axis probe adapted to measure magnetic fields in all directions (i.e. the x, y, and z directions). Examples include, but are not limited to, a Hall- effect probe, such as a Gaussmeter. It should however be understood that any other suitable probe may apply.

[0066] Figure 6 illustrates a measuring device 600 adapted to receive the output voltage measured by the sensing probe 1 14 and accordingly detect the magnitude and direction (i.e. the strength and polarity) of the local magnetic field. The device 600 may be secured to the system 100 of Figure 1 using a suitable attachment means 602. Alternatively, the device 600 may be handheld. The device 600 is adapted to receive via a suitable input means, such as a cable 604, input data from the sensing probe 1 14, the input data indicative of the output voltage measured as the probe 1 14 passes along the weld bead. The device 600 then computes the corresponding magnitude and direction of the local magnetic field and outputs the computed data to a suitable output means, such as a screen 606. In one embodiment, after use, the sensing probe 1 14 may be secured to the device 600 using a suitable attachment means, such as a grommet 608 extending away from an outer surface (not shown) of the device 600 and adapted to receive and retain the probe 1 14 therein. Other attachment means may apply.

[0067] Referring back to Figure 1 , in operation, as the frame 106 is driven along the welding path A, the sensing probe 1 14 and the shielding device 108 are moved synchronously adjacent the exposed surface (not shown) of the workpiece 102, with the sensing probe 1 14 being retained in the aperture 1 16 of the shielding device 108. As discussed above, the shielding device 108, which is positioned adjacent the weld region (not shown), generates a counterbalancing or nulling magnetic field that offsets the high ambient magnetic field present in the weld region. In this manner, the local ambient magnetic field is compensated for and reduced, thereby creating a low magnetic field zone at the weld region. Welding can therefore be facilitated and high quality welds obtained. In one embodiment, the local ambient magnetic field is reduced to a predetermined threshold, the threshold value being selected such that the local ambient magnetic field is sufficiently attenuated to stabilize the electric arc and facilitate welding.

[0068] As discussed above, the position and/or orientation of the shielding device 108 relative to the workpiece 102 can be adjusted dynamically so as to achieve the desired level of magnetic field attenuation (as measured by the sensing probe 1 14) while facilitating access to and visibility of the weld region. Indeed, by actuating (e.g. rotating) the attachment means 1 10 1 and/or 1 10 2 to which the shielding device 108 is secured, the angular and/or vertical position of the shielding device 108 relative to the workpiece 102, and accordingly to the electric arc, can be varied. In this manner, it is possible to vary the magnitude and/or polarity of the magnetic field generated by the shielding device 108. A desired level of magnetic field attenuation can therefore be achieved by adjusting the positioning of the shielding device 108 relative to the electric arc. For example, using the system 100, a magnetic field below 50 Gauss can be achieved.

[0069] The sensing probe 1 14 therefore measures the local magnetic field adjacent the weld bead and accordingly determines the position of the shielding device 108 that allows to achieve the level of magnetic field attenuation most suitable for the welding operation at hand. Once the position and orientation that achieves the desired level of magnetic field attenuation has been determined and the shielding device 108 locked in this position and orientation, the sensing probe 1 14 may be removed from the system 100 and the welding head 1 12 positioned in its place. The welding operation may then proceed at the low ambient magnetic field.

[0070] Using the system 100 of Figure 1 , both vertical and horizontal weld beads may be performed at low magnetic field levels. As also discussed above, although the system 100 of Figure 1 is described and illustrated herein as used to perform longitudinal welds along a linear path, non-longitudinal welds may also be performed along non-longitudinal paths. For this purpose, the system 100 may cause the welding head 1 12 and the shielding device 108 to move along a path stored in memory. Alternatively, the characteristics of the ambient magnetic field may be stored in memory and the system 100 may cause the welding head 1 12 and the shielding device 108 to move accordingly. Other embodiments may apply.

[0071 ] Moreover, the shielding device's position and orientation, which achieve the desired level of magnetic field attenuation, may be arrived at after one or more iterations. This is shown in Figure 7, which illustrates a method 700 for magnetic field shielding in a weld region where high ambient magnetic fields are present. At step 702, the shielding device (reference 108 in Figure 1) may be placed in a first position and orientation relative to the weld region. The resulting local magnetic field may then be measured at step 704 using the sensing probe (reference 1 14 in Figure 1 ) and a suitable measuring device, as discussed above. At step 704, the magnetic field measurement is compared to the magnetic field threshold to be reached and it is assessed at step 706 whether the measured magnetic field is within the threshold. If the threshold has not been reached, the position and/or orientation of the shielding device are adjusted accordingly (step 708) to cause the shielding device to generate a counterbalancing magnetic field that further reduces the local magnetic field. A new magnetic field measurement may then be obtained and compared to the threshold (step 704). As long as the threshold is not reached, the process (steps 704 to 708) is repeated. The final shielding device position and orientation are the position and orientation, which ensure that the magnetic field measurement meets the threshold. If the threshold has been reached, the welding head (reference 1 12 in Figure 1 ) is positioned adjacent the weld region in place of the sensing probe so the welding operation may proceed (step 710). It should be understood that, in some embodiments, it may be acceptable for the magnetic field measurement to be within a predetermined tolerance of the threshold.

[0072] It should also be understood that the various steps of the process of adjusting the position and/or orientation of the shielding device relative to the electric arc may be effected manually by an operator. Alternatively, the steps may be semi- or fully automated. For this purpose and as illustrated in Figure 8, a control system 800 may be used to perform real-time adjustment of the shielding device's position and orientation, and accordingly of the local ambient magnetic field. The control system 800 may comprise a controller 802, which is connected to a shielding device 804, a welding apparatus 806, and a magnetic field sensing probe 808. The welding apparatus 806 illustratively comprises a welding head (reference 1 12 in Figure 1) adapted to perform arc welds along a welding path.

[0073] The controller 802 may comprise a processing unit and a memory which has stored therein computer-executable instructions (none shown). The processing unit may comprise any suitable devices configured to cause a series of steps to be performed so as to implement the methods described herein. The processing unit may comprise, for example, any type of general-purpose microprocessor or microcontroller, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof. The memory may comprise any suitable known or other machine-readable storage medium. The memory may comprise any storage means (e.g. devices) suitable for retrievably storing machine-readable instructions executable by the processing unit. The computer-executable instructions may be in many forms, including program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0074] During the welding operation, the controller 802 may control the movement of the welding apparatus 806 along the weld path. The controller 802 may also set the shielding device 804 to an initial position and orientation relative to the weld region, as discussed above. The magnetic field sensing probe 808 may then continuously measure the local magnetic field at the weld region and provide the controller 802 with the magnetic field measurement. The controller 802 may compare the received magnetic field measurement to a predetermined magnetic field threshold to determine whether further adjustment of the position and/or orientation of the shielding device 804 is required. If this is the case, i.e. the local magnetic field is not sufficiently reduced to achieve high quality welds, the controller 802 may output a control signal to the shielding device 804 to cause adjustment of the position and/or orientation of the shielding device accordingly. A new measurement of the local magnetic field may then be obtained by the magnetic field sensing probe 808 and sent to the controller 802 in real-time. The process may then repeat until a final shielding device position and orientation, which ensures that the local magnetic field is within the threshold, is reached, as discussed above. In this manner, welding is facilitated and high quality welds can be obtained.

[0075] Various aspects of the methods and systems for magnetic field shielding in a weld region disclosed herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, changes and modifications may be made. The scope of the following claims should not be limited by the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the description as a whole.