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WO2006084323A1 - Improvements in electric arc welding - Google Patents

Improvements in electric arc welding Download PDF

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Publication number
WO2006084323A1
WO2006084323A1 PCT/AU2006/000166 AU2006000166W WO2006084323A1 WO 2006084323 A1 WO2006084323 A1 WO 2006084323A1 AU 2006000166 W AU2006000166 W AU 2006000166W WO 2006084323 A1 WO2006084323 A1 WO 2006084323A1
Authority
WO
WIPO (PCT)
Prior art keywords
shielding member
piece
electrode
work
shielding
Prior art date
Application number
PCT/AU2006/000166
Other languages
French (fr)
Inventor
Wojciech Mazur
Brian Laurence Jarvis
Tan Minh Doan
George Jerzy Syrek
Original Assignee
Commonwealth Scientific And Industrial Research Organisation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2005900623A external-priority patent/AU2005900623A0/en
Application filed by Commonwealth Scientific And Industrial Research Organisation filed Critical Commonwealth Scientific And Industrial Research Organisation
Publication of WO2006084323A1 publication Critical patent/WO2006084323A1/en

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/32Accessories
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/06Arrangements or circuits for starting the arc, e.g. by generating ignition voltage, or for stabilising the arc
    • B23K9/073Stabilising the arc

Definitions

  • This invention relates to improvements in or relating to electric arc welding which facilitate welding in strong magnetic fields.
  • the present invention relates to a shielding member and a method of shielding an electric arc from a strong magnetic field.
  • the welding arc can be deflected forwardly or rearwardly with respect to the welding direction, or laterally to one or the other side of the welding direction. Deflection of the arc in the welding direction can be beneficial.
  • a proposal for such deflection is provided in British patent GB-699944.
  • the arc current magnetises a split ring of a magnetisable alloy with the arc being deflected in the direction of the split in the ring by the resultant magnetic field generated by the magnetism induced in the ring.
  • the ring is made from a magnetisable alloy, rather than a permanent magnet, due to the relatively low Curie temperature at which permanent magnetism is lost in the absence of an applied field.
  • An alternative approach, utilising laterally aligned magnetic poles is disclosed in US patent 3626145 to Jackson.
  • unidirectional fields have been applied to an AC arc to oscillate the arc laterally across the welding direction, such as to enhance gas tungsten or gas metal arc welding (GTAW or GMAW).
  • GTAW gas tungsten or gas metal arc welding
  • an alternating magnetic field can be applied to a DC arc for the same purpose.
  • the above examples of an induced or applied magnetic field are controlled and utilise a magnetic field of quite low value or strength, that is, up to about 40 Gauss.
  • large scale magnetic fields which have strengths an order of magnitude greater than those low values. For example, in aluminium smelters strong DC magnetic fields up to and in excess of 400 Gauss prevail. Field strengths of this order are reported to be so strong as to pull metal objects out of the trouser pockets of workers operating the plant and even make their watches stop.
  • a screening ring can be characterised by its screening factor SF as:
  • SF B O /B S
  • B 0 is the component of the magnetic field outside the ring
  • B s is the component inside the ring.
  • the shielding rings have to be moved to follow the arc as welding progresses to enable effective screening at successive sections along a weld seam, as they protect from magnetic fields only at a localised area within the ring.
  • the shielding rings are relatively heavy due to the need for them to be of steel or other ferromagnetic material, and to enclose an operating area which is of a size which does not impede welding.
  • the shielding rings usually have at least one handle by which they can be moved along a weld seam in the course of welding.
  • the rings are somewhat cumbersome and, in some situations, they can be difficult to manoeuvre.
  • the present invention is directed to providing improvements in or relating to electric arc welding which facilitates welding in strong magnetic fields.
  • the present invention provides a shielding member suitable for use in welding in a strong magnetic field.
  • the shielding member has a body which, at a first (usually the upper) one of opposite ends thereof, is able to extend from the gas nozzle of an electric arc welding torch in spaced relation to an end portion of the electrode projecting from the torch, beyond the nozzle.
  • the body has a shape such that, as so extending from the nozzle, the body extends at least a major part of the way around the end portion of the electrode.
  • the body is of a ferromagnetic material and is adapted to locally distort the magnetic field whereby the end portion of the electrode and an arc struck between the electrode and a work-piece are substantially shielded from the magnetic field.
  • the shielding member of the invention made of ferromagnetic material may be secured to the torch gas nozzle which is generally made of non-ferromagnetic material as a permanent attachment.
  • the shielding member is releasably securable to the nozzle.
  • the member preferably includes suitable means for releasably retaining the body in relation to the nozzle.
  • the shielding member and torch gas nozzle may be formed in one piece entirely of ferromagnetic material.
  • the shielding member may extend from within the nozzle. However, it is preferred that the shielding member extends around the exterior of the nozzle.
  • the nozzle of an electric arc welding torch typically is of a refractory thermal insulator, such as a ceramic material, or a good thermal conductor, such as copper.
  • the shielding member is to provide shielding for the end portion of the electrode projecting from the nozzle and for droplets of weld metal, at least until the droplets are released from the electrode. Once droplets are released, they no longer conduct current and they therefore are able to travel without risk of being deflected by the magnetic field. However, the arc itself still is able to be deflected and it therefore is highly desirable that the body of the shielding member is able to extend from the nozzle, beyond the end portion of the electrode, to shield the arc from the magnetic field.
  • the arrangement may be such that the body extends so as to conform to the profile of a work-piece being welded, or with at least one of work-pieces to be joined by a weld.
  • the body of the shielding member can take a wide variety of forms, depending on the nature of the weld to be produced.
  • the body In a first simple form, suitable for a butt joint between members aligned approximately in the same plane, or a shallow groove weld between work pieces, the body may be of circular cross- section intermediate the opposite ends. In that form, the body may be substantially cylindrical.
  • the shielding member At the second (usually the lower) one of the opposite ends, that is, the end remote from the upper end at or securable to the nozzle, the body may bear against the surfaces between which a weld is to be produced.
  • the shielding member is able to provide shielding over at least a major part of the length of the arc from the electrode.
  • the welding torch on which the shielding member is provided is able to traverse the weld seam with the lower end of the body of that member closely adjacent to or sliding over the work-piece surfaces to the sides of the seam.
  • the body may have a projecting tab, or "beak", of a shape corresponding to the profile of a groove along the weld seam to further protect the arc.
  • Weld metal deposited in the groove usually precludes a similar tab or beak at the trailing side of the body.
  • a variant of the first simple form provides a shielding member suitable for use in welding to lay down a weld bead on a work-piece surface.
  • the lower end of the shielding member may be substantially planar for a flat work-piece surface or, if that surface is arcuate laterally of the intended bead line, the lower end may be of complementary form.
  • a notch is formed in the lower end. The shape of the notch is complementary to the shape of the resultant weld metal built up on the work-piece surface resulting from the weld bead, to enable the shielding member to be moved along the bead line.
  • the lower end of the body preferably is in close proximity to the work-piece surface as the shielding member is moved during the laying down of the weld bead, freshly deposited weld metal is not contacted by the body.
  • the clearance between the notch and freshly deposited weld metal preferably is kept to a minimum in order to maximise shielding provided by the body.
  • a second form of the shielding member of the present invention is suited for producing fillet welds, whether in a lap joint, a T-joint or a corner joint, but also can be used to produce bead on plate welds or butt welds. That is, the second form is suitable for producing a weld of approximately triangular cross-section for joining work-pieces at respective surfaces at an angle to each other, such as substantially at right angles.
  • the body of the shielding member has a U-shaped cross-section in planes extending perpendicular to the torch axis, that is, transversely with respect to a line extending between the first and second ends. The body may have such U-shape through to each of its upper and lower ends although, as an alternative to this, the upper end may be at an annular collar by which the shielding member is securable to the nozzle of a welding torch.
  • the lower end of the body faces, and preferably abuts, a first one of the two surfaces between which a fillet weld is to be produced. Due to the U-shaped cross-section, the body has two side flanges or arms and an edge or end of each of these flanges or arms faces, and preferably abuts, the second one of the two surfaces.
  • the U-shaped cross- section results in the body of the shielding member not fully circumferentially enclosing the electrode and an arc generated by a welding torch to which the shielding member is fitted, adequate shielding of the electrode and arc is able to be achieved by positioning the shielding member closely adjacent to or in contact with the first and second surfaces between which the fillet weld is to be produced. That is, the shielding member conforms to and co-operates with the work-pieces to achieve the required shielding.
  • each side flange of the body may be adjustable.
  • a respective elongate plate may be adjustably mounted on each flange, along the edge of each flange which faces the second of the surfaces between which a fillet weld is required. In that case, an edge of each plate is able to be closely adjacent to or in contact with the second surface.
  • the plates are adjustable so that the lateral spacing between the electrode and the second surface can be varied as required within the limit of adjustability of one or each plate.
  • the electrode of the welding torch is at an acute angle to each of the surfaces between which a fillet weld is to be produced.
  • the side flanges of the body are tapered such that the body decreases in cross- section towards the lower end.
  • the shielding member of the present invention may be used to shield a welding arc produced by a variety of power sources including direct current (DC), pulsed DC and alternating current (AC) including pulsed AC and variable-polarity power sources.
  • a shielding member for shielding an electric arc from a relatively strong magnetic field, said electric arc being struck between an electrode and a work-piece, said shielding member including a main body adapted to extend at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
  • a method of shielding an electric arc from a relatively strong magnetic field said electric arc being struck between an electrode and a work-piece, said method including applying a shielding member at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
  • Figure 1 is a schematic representation of a change in magnetic field distribution resulting from use of a shielding member according to the present invention
  • Figure 2 illustrates the distribution of magnetic flux density around a shielding member of the form schematically illustrated in Figure 1 (yz - plane);
  • Figure 3 illustrates six numbered shielding members in the order of 0, 1 , 3, 5, 4, 2, with member number 5 shown as fitted to the lower end of a gas nozzle;
  • Figures 4 to 12 illustrate further members numbered 6 to 8 and 10 to 15, respectively;
  • Figure 13 shows a prior art shielding ring 16
  • Figures 14 to 17 illustrate further members 17, 18, 18P (as for No. 18 but with side plates) and 19 (for fillet welds in lap joints), respectively;
  • Figure 18 schematically illustrates member No. 19 of Figure 17 as arranged for producing a fillet weld
  • Figure 19 illustrates a still further member No. 20 suitable for manual welding of fillet welds
  • Figures 20 and 21 schematically illustrate electrode positions in producing a fillet weld with shielding member No. 14 of Figure 1 1 ;
  • Figure 22 illustrates a fillet weld produced without shielding in a magnetic field of 100G
  • Figure 23 illustrates a fillet weld produced with shielding member No. 14 in a magnetic field of 400G;
  • Figures 24 and 25 illustrate cross-sections of the fillet welds of Figures 22 and 23, respectively;
  • Figure 26 illustrates the magnetic flux density distribution (yz - plane) around U-shaped shielding member No. 17 of Figure 14;
  • Figure 27 is a plot of magnetic flux distribution from the centre of the member No. 17 of Figure 14;
  • Figure 28 is similar to Figure 2, but illustrates flux density (yz - plane) for a cylindrical shielding member of the same material, thickness and height as member No. 17 of Figure 14;
  • Figure 29 is similar to Figure 27, but is in respect of the same member as Figure 28;
  • Figure 30 is a plot of magnetic flux density against distance below the shielding member for member No. 17 of Figure 14 and for the same member as Figure 28;
  • FIGS 31 and 32 illustrate further shielding members Nos. 24 and 25 used for manual welding of bead on plate and fillet welds respectively;
  • Figures 33 to 35 illustrate fillet welds produced without shielding in magnetic fields of 100G, 150G and 200G respectively;
  • Figures 36 to 38 illustrate fillet welds produced with shielding member No. 25 in magnetic fields of 400G, 550G and 600G respectively;
  • Figures 39 and 40 illustrate members Nos. 24 and 25 of Figures 31 and 32 with ceramic inserts.
  • FIG. 1 schematically illustrates an arrangement for deposition of a weld bead on a work-piece W, using a GMAW torch T.
  • the torch T has a body (5) which is fitted with a gas nozzle (1 ) such as of a refractory non-magnetic material or a heat conductive, non-magnetic material, such as copper.
  • a consumable electrode (3) is supplied through the torch body (5) and projects through and a short distance beyond the lower end of nozzle (1 ).
  • An electric arc (4) is shown as having been struck between electrode (3) and the work- piece W.
  • the arrangement is conventional.
  • the arrangement of Figure 1 further includes a shielding member (2) according to the present invention.
  • the member (2) comprises a ferromagnetic cylinder which, at one end, is secured on the lower end of nozzle (1 ) so as to be disposed concentrically around the projecting end of electrode (3).
  • Figure 1 shows the arrangement in use in a strong magnetic field.
  • the field is depicted in a first form in which it exists if member (2) is not present. That first form is shown by the fainter set of lines which represent magnetic field strength lines that extend parallel to the surface of work-piece W on which a weld bead is to be produced.
  • that surface is in the x-y plane of an x, y, z co-ordinate system in which the z-axis is perpendicular to the work-piece surface.
  • the magnetic field strength lines are shown by the heavier lines which, at their ends to the left of Figure 1 , are provided with arrow-heads. These lines depict the magnetic field as modified from the first form by the presence of shielding member (2). As depicted, the member (2) locally distorts the magnetic field, forming a bell-shaped "cavity" in the magnetic field strength lines within member (2).
  • the magnetic field is able to deflect the arc to the left or right (depending on the direction of the magnetic field).
  • the shielding member (2) in modifying the magnetic field, results in the field being reduced to a level within shielding member (2) such that deflection of the arc is able to be avoided or significantly reduced. That is, distortion of the magnetic field to produce the bell-shaped "cavity" diminishes the magnetic field in the vicinity of the arc where it otherwise would be most disruptive of deposition of weld metal.
  • the torch T remains as easy to handle and operate as it is in traditional GMAW.
  • the torch T remains suitable for manual, semi-automatic, mechanised or robotic welding.
  • No additional supply of power or cooling to the shielding member (2) is needed.
  • the added cost of shielding member (2) is modest, particularly compared to the cost benefits it is able to provide in welding in strong magnetic fields.
  • the shielding member (2) is able to be made of low cost ferromagnetic material, such as a suitable machineable steel.
  • the shielding member (2) can be made to a shape suitable for various gas nozzles used with different types of GMAW and GTAW torches. Also, the shape can be varied to suit different types of welds. In each case, given that the shielding member (2) is of ferromagnetic material, it preferably is internally provided with a coating, such as of copper or other anti-spatter material, for preventing spatter from adhering.
  • the shielding factor SF (that is, B 0 /B s ) depends on the distance from the lower end of the shield member and on the wall thickness of the body.
  • the shielding factor is not significantly influenced by the permeability of the ferromagnetic material of which the body is made, at least for practical wall thicknesses for the body.
  • FIG. 2 An example of magnetic flux density distribution around a cylindrical shielding member (2) is shown in Figure 2.
  • shielding member (2) is shown as sectioned through the z axis.
  • the y-z plane is illustrated with shielding member (2) in the same orientation as shown in Figure 1.
  • the shielding member (2) was made of mild steel having a permeability ⁇ of 4000H/m, an internal diameter of 20 mm, a wall thickness of 8 mm and a length of 20 mm.
  • the magnetic field for which the variation in flux density is shown in Figure 2 had a strength of 400 Gauss. As is evident from Figure 2, the field strength is very substantially reduced within and outside of the shielding member (2).
  • the strongest reduction in the magnetic field is inside the shielding member.
  • Modelling indicates that, with variation in wall thickness of the body of the shielding member, the shielding factor at the lower end of the shielding member should increase from 4.8 at a wall thickness of 2 mm to 12.6 at a wall thickness of 16 mm. This represents a decrease in the magnetic flux density at the lower end of the shielding member, from the external value of 400 Gauss, to a level of 83.5 Gauss for the wall thickness of 2 mm and a level of 31.7 Gauss for the wall thickness of 16 mm.
  • Table I Table I
  • Table Il provides a comparison of predicted and measured screening factors.
  • the invention enables completion of good quality welds in areas where strong magnetic fields are present.
  • One particular example where use of the invention is beneficial is within aluminium smelters, where strong reactions between the current in welding arcs and the magnetic field can preclude good welding with conventional procedures and equipment.
  • the shielding member can have various shapes including:
  • member number 4 is of circular cross-section between their top and bottom, that is between their upper and lower ends, although some show a taper to the second end. Member number 4 is shown as cut away, such as to enable deposition of a weld bead close to an upstanding ledge.
  • the wall thickness "t", height "h” and internal diameter "d" for each of the members of Figure 3 are shown in an adjacent table.
  • member No. 6 of Figure 4 is of penannular form, having a slit of width s as detailed in the adjacent table to improve arc visibility.
  • Members Nos. 7 and 8 of Figures 5 and 6 show respective forms of cut-out enabling specific welding requirements to be accommodated.
  • Members Nos. 1 1 to 14 of Figures 8 to 11 show further variants, with members Nos. 12 and 14 being for production of fillet welds, and member No. 13 enabling a weld bead deposit on the surface of a work-piece.
  • Member No. 10 of Figure 7 is of a modified cylindrical form, in being formed as a helical coil of 4.8 mm diameter rod.
  • Member No. 10 is connectable to the nozzle of a welding torch by a projecting upper end of the rod, while the lowest loop of the rod where it would encircle the welding arc is closed.
  • member No. 10 can achieve a useful reduction in magnetic field strength such as to substantially prevent arc deflection.
  • Member No. 15 of Figure 12 is a simplified version of member No. 10.
  • the member No. 15 simply comprises a closed loop (circle) of 4.8 mm diameter rod, from which an upstanding end of the rod enables connection to a nozzle as shown.
  • FIG 13 shows a manually adjustable shielding frame (shield No. 16) according to current practice, rather than a shielding member according to the present invention.
  • the shielding frame is made up of bars which have a diameter of 32 mm and which are welded together to form a rectangular frame. At opposite longitudinal sides, the frame is provided with handles by which the frame is able to be moved manually.
  • the frame encloses an operating area of 265 mm by 165 mm within which welding is to be conducted.
  • Shielding members Nos. 17, 18, 18P and 19, shown respectively in Figures 14 to 17, show further configurations for producing welds in specific situations.
  • Members Nos. 18, 18P and 19, for example, are suitable for producing fillet welds, such as illustrated in Figure 18, or for T-joints. In each case, these members are of U-shape and are able to provide arc shielding by their opposed side flanges.
  • Figure 18 illustrates an upright arrangement in which a fillet weld, shown in solid form is produced between overlapping plates.
  • FIGS. 18 and 18P show tapered bodies which enable an electrode and arc to be presented at an acute angle to each of mutually perpendicular surfaces to be joined by a fillet weld such as in T-joints.
  • Member No. 20 of Figure 19 is shown as having a lower end formed by oblique cuts to provide adjacent edges for contacting such surfaces and thereby present the electrode and arc in such manner for producing a fillet weld.
  • Figures 26 and 28 illustrate the magnetic flux density distribution (y-z plane) for two shielding members according to the invention which differ in that the member for Figure 26 is U-shaped, whereas the member for Figure 28 is cylindrical.
  • the member for Figure 26 is member number 17 shown in Figure 14, which was made of steel and had a wall thickness of 8 mm, a height of 30 mm and a depth parallel to its side flanges of 24 mm.
  • the member had a permeability ⁇ of 4000 H/m and the distribution of Figures 26 and 27 was obtained with an external magnetic field strength of 400 Gauss.
  • the cylindrical member for Figures 28 and 29 was of the same material and of corresponding dimensions, and the distribution of Figure 28 also was obtained with a field strength of 400 Gauss.
  • Table V which, in the lower half also details the increase in flux density with increasing distance from zero to 20 mm below the base or lower end of each of the shielding members.
  • the details shown in the lower half of Table V are shown graphically in Figure 30 for the respective shielding members, illustrating their comparable performance.
  • Figures 27 and 29 show a plot of magnetic flux density distribution against distance from the centre of the respective shielding members of Figures 26 and 28. Again, comparable performance of the members is evident from a comparison of Figures 27 and 29.
  • the flux density is shown in Tesla (10 4 Gauss), while distance is shown in metres.
  • the fillet welds made with an AC- MIG process in the magnetic field of 100-200 Gauss with no magnetic shielding or 400-600 Gauss with the torch shield No 25 are very similar in their quality. These indicate a good shielding efficiency of the torch shielding member of the invention used for welding a strong magnetic field, such as 600 Gauss.
  • a further improvement to the shielding member may be achieved by ensuring that it remains electrically insulated from the work-piece. This may be achieved by inserting ceramic rods 39, 40 into the body of the shield, such that the ends of the rods protrude slightly preventing electrical contact between the work- piece and the shield during manual operation (refer Figures 39 and 40). This addition also assists in maintaining a constant spacing between the shield and work-piece. When ceramic rods are not present minor arcing may occur between the shield and the work-piece and this may interfere with free movement of the torch, particularly during manual welding with AC-MIG.

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  • Arc Welding In General (AREA)

Abstract

A shielding member is disclosed for shielding an electric arc from a strong magnetic field, the electric arc being struck between an electrode and a work- piece. The shielding member includes a main body adapted to extend at least a major part around an end portion of the electrode to substantially shield the end portion and/or the electric arc from the magnetic field. A method of shielding an electric arc from a strong magnetic field is also disclosed.

Description

IMPROVEMENTS IN ELECTRIC ARC WELDING
Field of the Invention
This invention relates to improvements in or relating to electric arc welding which facilitate welding in strong magnetic fields. In particular the present invention relates to a shielding member and a method of shielding an electric arc from a strong magnetic field.
Background to the Invention In electric arc welding, the welding arc is deflected if subjected to an external magnetic field, due to the field interacting with the flow of current and the flow of charged particles in the arc plasma. This is because a conductor such as the arc, which carries a current through an external magnetic field, experiences an electromagnetic (Lorentz) force which is mutually perpendicular to the respective direction of the current and the magnetic field.
Depending on the direction of the external magnetic field, the welding arc can be deflected forwardly or rearwardly with respect to the welding direction, or laterally to one or the other side of the welding direction. Deflection of the arc in the welding direction can be beneficial. A proposal for such deflection is provided in British patent GB-699944. In that proposal, the arc current magnetises a split ring of a magnetisable alloy, with the arc being deflected in the direction of the split in the ring by the resultant magnetic field generated by the magnetism induced in the ring. The ring is made from a magnetisable alloy, rather than a permanent magnet, due to the relatively low Curie temperature at which permanent magnetism is lost in the absence of an applied field. An alternative approach, utilising laterally aligned magnetic poles is disclosed in US patent 3626145 to Jackson.
In other contexts, unidirectional fields have been applied to an AC arc to oscillate the arc laterally across the welding direction, such as to enhance gas tungsten or gas metal arc welding (GTAW or GMAW). Conversely, an alternating magnetic field can be applied to a DC arc for the same purpose. The above examples of an induced or applied magnetic field are controlled and utilise a magnetic field of quite low value or strength, that is, up to about 40 Gauss. However, there are industrial plants in which large scale magnetic fields are generated which have strengths an order of magnitude greater than those low values. For example, in aluminium smelters strong DC magnetic fields up to and in excess of 400 Gauss prevail. Field strengths of this order are reported to be so strong as to pull metal objects out of the trouser pockets of workers operating the plant and even make their watches stop.
The strong magnetic fields generated in some industrial plants, such as aluminium smelters, make it extremely difficult to carry out welding work to a suitable standard. Welding becomes very erratic, and sometimes is almost impossible. Nevertheless, the weld quality can be very important as, for example, for welding between steel tail connections to cathode bars (also of steel), or between aluminium plates of busbars and of risers for supplying current to anodes, the weld quality is important. Welded joints of low quality reduce the operating efficiency of the plant and result in considerable loss of processing power. To eliminate the harmful effect of magnetic fields while welding, the processing power of an aluminium smelter would need to be reduced to or below 40% of its normal value or even to be completely switched off. However, such power interruption can not be allowed due to the dramatic effect it could have on plant productivity.
Where possible, welding in strong magnetic fields is conducted with use of a portable shielding ring. These consist of a relatively large open frame of ferromagnetic material which encloses an operating area in which a weld can be laid. The shielding ring is positioned over a work piece and moved along the weld seam in the course of welding. The rings commonly are formed of steel tubing typically from 25 mm to 35 mm in internal diameter. The frame of a shielding ring may extend around an operating area of about 130 mm by 70 mm to about 230 mm by 140 mm, although they occasionally may be larger. Where such screening rings are able to be usefully employed, they enable a reduction in harmful effects of external magnetic fields on arc stability. A screening ring can be characterised by its screening factor SF as:
SF=BO/BS where B0 is the component of the magnetic field outside the ring and Bs is the component inside the ring. The shielding rings have to be moved to follow the arc as welding progresses to enable effective screening at successive sections along a weld seam, as they protect from magnetic fields only at a localised area within the ring.
The shielding rings are relatively heavy due to the need for them to be of steel or other ferromagnetic material, and to enclose an operating area which is of a size which does not impede welding. The shielding rings usually have at least one handle by which they can be moved along a weld seam in the course of welding. However, despite having handles, the rings are somewhat cumbersome and, in some situations, they can be difficult to manoeuvre. Also, there are many situations in which the type of weld to be produced, or the very limited access, precludes the effective use of the shielding rings at all.
The present invention is directed to providing improvements in or relating to electric arc welding which facilitates welding in strong magnetic fields.
Broad Summary of the Invention The present invention provides a shielding member suitable for use in welding in a strong magnetic field. The shielding member has a body which, at a first (usually the upper) one of opposite ends thereof, is able to extend from the gas nozzle of an electric arc welding torch in spaced relation to an end portion of the electrode projecting from the torch, beyond the nozzle. The body has a shape such that, as so extending from the nozzle, the body extends at least a major part of the way around the end portion of the electrode. The body is of a ferromagnetic material and is adapted to locally distort the magnetic field whereby the end portion of the electrode and an arc struck between the electrode and a work-piece are substantially shielded from the magnetic field. The shielding member of the invention made of ferromagnetic material may be secured to the torch gas nozzle which is generally made of non-ferromagnetic material as a permanent attachment. However, as detailed herein, it can be beneficial to use different shielding members for different weld types. Thus, rather than needing to replace a nozzle/shielding member combination to enable this, it is preferable that the shielding member is releasably securable to the nozzle. Thus the member preferably includes suitable means for releasably retaining the body in relation to the nozzle. In some embodiments the shielding member and torch gas nozzle may be formed in one piece entirely of ferromagnetic material.
The shielding member may extend from within the nozzle. However, it is preferred that the shielding member extends around the exterior of the nozzle. As will be appreciated, the nozzle of an electric arc welding torch typically is of a refractory thermal insulator, such as a ceramic material, or a good thermal conductor, such as copper.
In use, the shielding member is to provide shielding for the end portion of the electrode projecting from the nozzle and for droplets of weld metal, at least until the droplets are released from the electrode. Once droplets are released, they no longer conduct current and they therefore are able to travel without risk of being deflected by the magnetic field. However, the arc itself still is able to be deflected and it therefore is highly desirable that the body of the shielding member is able to extend from the nozzle, beyond the end portion of the electrode, to shield the arc from the magnetic field. The arrangement may be such that the body extends so as to conform to the profile of a work-piece being welded, or with at least one of work-pieces to be joined by a weld.
The body of the shielding member can take a wide variety of forms, depending on the nature of the weld to be produced. In a first simple form, suitable for a butt joint between members aligned approximately in the same plane, or a shallow groove weld between work pieces, the body may be of circular cross- section intermediate the opposite ends. In that form, the body may be substantially cylindrical. At the second (usually the lower) one of the opposite ends, that is, the end remote from the upper end at or securable to the nozzle, the body may bear against the surfaces between which a weld is to be produced. Thus, the shielding member is able to provide shielding over at least a major part of the length of the arc from the electrode. In producing a weld, the welding torch on which the shielding member is provided is able to traverse the weld seam with the lower end of the body of that member closely adjacent to or sliding over the work-piece surfaces to the sides of the seam. At a leading side of the body relative to movement during welding, the body may have a projecting tab, or "beak", of a shape corresponding to the profile of a groove along the weld seam to further protect the arc. Weld metal deposited in the groove usually precludes a similar tab or beak at the trailing side of the body.
A variant of the first simple form provides a shielding member suitable for use in welding to lay down a weld bead on a work-piece surface. The lower end of the shielding member may be substantially planar for a flat work-piece surface or, if that surface is arcuate laterally of the intended bead line, the lower end may be of complementary form. However, at a trailing side of the shielding member body relative to movement during welding, a notch is formed in the lower end. The shape of the notch is complementary to the shape of the resultant weld metal built up on the work-piece surface resulting from the weld bead, to enable the shielding member to be moved along the bead line. Thus, while the lower end of the body preferably is in close proximity to the work-piece surface as the shielding member is moved during the laying down of the weld bead, freshly deposited weld metal is not contacted by the body. However, the clearance between the notch and freshly deposited weld metal preferably is kept to a minimum in order to maximise shielding provided by the body.
A second form of the shielding member of the present invention is suited for producing fillet welds, whether in a lap joint, a T-joint or a corner joint, but also can be used to produce bead on plate welds or butt welds. That is, the second form is suitable for producing a weld of approximately triangular cross-section for joining work-pieces at respective surfaces at an angle to each other, such as substantially at right angles. In that second form, the body of the shielding member has a U-shaped cross-section in planes extending perpendicular to the torch axis, that is, transversely with respect to a line extending between the first and second ends. The body may have such U-shape through to each of its upper and lower ends although, as an alternative to this, the upper end may be at an annular collar by which the shielding member is securable to the nozzle of a welding torch.
In use of the second form, the lower end of the body faces, and preferably abuts, a first one of the two surfaces between which a fillet weld is to be produced. Due to the U-shaped cross-section, the body has two side flanges or arms and an edge or end of each of these flanges or arms faces, and preferably abuts, the second one of the two surfaces. Thus, while the U-shaped cross- section results in the body of the shielding member not fully circumferentially enclosing the electrode and an arc generated by a welding torch to which the shielding member is fitted, adequate shielding of the electrode and arc is able to be achieved by positioning the shielding member closely adjacent to or in contact with the first and second surfaces between which the fillet weld is to be produced. That is, the shielding member conforms to and co-operates with the work-pieces to achieve the required shielding.
In a variant on the second form, each side flange of the body may be adjustable. For this, a respective elongate plate may be adjustably mounted on each flange, along the edge of each flange which faces the second of the surfaces between which a fillet weld is required. In that case, an edge of each plate is able to be closely adjacent to or in contact with the second surface. The plates are adjustable so that the lateral spacing between the electrode and the second surface can be varied as required within the limit of adjustability of one or each plate.
In the second form of the shielding member, and the variant thereof, it can be desirable that the electrode of the welding torch is at an acute angle to each of the surfaces between which a fillet weld is to be produced. To enable this, the side flanges of the body are tapered such that the body decreases in cross- section towards the lower end. As will be appreciated by those skilled in the art, the shielding member of the present invention may be used to shield a welding arc produced by a variety of power sources including direct current (DC), pulsed DC and alternating current (AC) including pulsed AC and variable-polarity power sources.
Since deflection of the welding arc by an external magnetic field is related to the direction of current flow within the welding arc, periodic reversal of current as occurs with AC power sources may reduce sensitivity of the welding arc to the external magnetic field. At the very least it may raise the threshold at which it may be possible to complete welds of acceptable quality without arc shielding.
According to one aspect of the present invention there is provided a shielding member for shielding an electric arc from a relatively strong magnetic field, said electric arc being struck between an electrode and a work-piece, said shielding member including a main body adapted to extend at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
According to a further aspect of the present invention there is provided a method of shielding an electric arc from a relatively strong magnetic field, said electric arc being struck between an electrode and a work-piece, said method including applying a shielding member at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
General Description of the Drawings
In order that the invention may more readily be understood, reference now is directed to the accompanying drawings, in which:
Figure 1 is a schematic representation of a change in magnetic field distribution resulting from use of a shielding member according to the present invention; Figure 2 illustrates the distribution of magnetic flux density around a shielding member of the form schematically illustrated in Figure 1 (yz - plane);
Figure 3 illustrates six numbered shielding members in the order of 0, 1 , 3, 5, 4, 2, with member number 5 shown as fitted to the lower end of a gas nozzle;
Figures 4 to 12 illustrate further members numbered 6 to 8 and 10 to 15, respectively;
Figure 13 shows a prior art shielding ring 16;
Figures 14 to 17 illustrate further members 17, 18, 18P (as for No. 18 but with side plates) and 19 (for fillet welds in lap joints), respectively;
Figure 18 schematically illustrates member No. 19 of Figure 17 as arranged for producing a fillet weld;
Figure 19 illustrates a still further member No. 20 suitable for manual welding of fillet welds;
Figures 20 and 21 schematically illustrate electrode positions in producing a fillet weld with shielding member No. 14 of Figure 1 1 ;
Figure 22 illustrates a fillet weld produced without shielding in a magnetic field of 100G;
Figure 23 illustrates a fillet weld produced with shielding member No. 14 in a magnetic field of 400G;
Figures 24 and 25 illustrate cross-sections of the fillet welds of Figures 22 and 23, respectively; Figure 26 illustrates the magnetic flux density distribution (yz - plane) around U-shaped shielding member No. 17 of Figure 14;
Figure 27 is a plot of magnetic flux distribution from the centre of the member No. 17 of Figure 14;
Figure 28 is similar to Figure 2, but illustrates flux density (yz - plane) for a cylindrical shielding member of the same material, thickness and height as member No. 17 of Figure 14;
Figure 29 is similar to Figure 27, but is in respect of the same member as Figure 28;
Figure 30 is a plot of magnetic flux density against distance below the shielding member for member No. 17 of Figure 14 and for the same member as Figure 28;
Figures 31 and 32 illustrate further shielding members Nos. 24 and 25 used for manual welding of bead on plate and fillet welds respectively;
Figures 33 to 35 illustrate fillet welds produced without shielding in magnetic fields of 100G, 150G and 200G respectively;
Figures 36 to 38 illustrate fillet welds produced with shielding member No. 25 in magnetic fields of 400G, 550G and 600G respectively; and
Figures 39 and 40 illustrate members Nos. 24 and 25 of Figures 31 and 32 with ceramic inserts.
Detailed Description of the Drawings
Figure 1 schematically illustrates an arrangement for deposition of a weld bead on a work-piece W, using a GMAW torch T. As shown, the torch T has a body (5) which is fitted with a gas nozzle (1 ) such as of a refractory non-magnetic material or a heat conductive, non-magnetic material, such as copper. A consumable electrode (3) is supplied through the torch body (5) and projects through and a short distance beyond the lower end of nozzle (1 ). An electric arc (4) is shown as having been struck between electrode (3) and the work- piece W. To this extent, the arrangement is conventional.
The arrangement of Figure 1 further includes a shielding member (2) according to the present invention. The member (2) comprises a ferromagnetic cylinder which, at one end, is secured on the lower end of nozzle (1 ) so as to be disposed concentrically around the projecting end of electrode (3).
The schematic illustration of Figure 1 shows the arrangement in use in a strong magnetic field. The field is depicted in a first form in which it exists if member (2) is not present. That first form is shown by the fainter set of lines which represent magnetic field strength lines that extend parallel to the surface of work-piece W on which a weld bead is to be produced. In the convention followed herein, that surface is in the x-y plane of an x, y, z co-ordinate system in which the z-axis is perpendicular to the work-piece surface.
In a second form, the magnetic field strength lines are shown by the heavier lines which, at their ends to the left of Figure 1 , are provided with arrow-heads. These lines depict the magnetic field as modified from the first form by the presence of shielding member (2). As depicted, the member (2) locally distorts the magnetic field, forming a bell-shaped "cavity" in the magnetic field strength lines within member (2).
In the absence of the shielding member (2), the magnetic field is able to deflect the arc to the left or right (depending on the direction of the magnetic field). However, the shielding member (2), in modifying the magnetic field, results in the field being reduced to a level within shielding member (2) such that deflection of the arc is able to be avoided or significantly reduced. That is, distortion of the magnetic field to produce the bell-shaped "cavity" diminishes the magnetic field in the vicinity of the arc where it otherwise would be most disruptive of deposition of weld metal. In addition to the shielding member (2) being able to greatly diminish the magnetic field in the arc zone, the torch T remains as easy to handle and operate as it is in traditional GMAW. That is, the torch T remains suitable for manual, semi-automatic, mechanised or robotic welding. No additional supply of power or cooling to the shielding member (2) is needed. Also, the added cost of shielding member (2) is modest, particularly compared to the cost benefits it is able to provide in welding in strong magnetic fields. Thus, the shielding member (2) is able to be made of low cost ferromagnetic material, such as a suitable machineable steel.
The shielding member (2) can be made to a shape suitable for various gas nozzles used with different types of GMAW and GTAW torches. Also, the shape can be varied to suit different types of welds. In each case, given that the shielding member (2) is of ferromagnetic material, it preferably is internally provided with a coating, such as of copper or other anti-spatter material, for preventing spatter from adhering.
Performance of shielding members according to the present invention has been confirmed by numerical modelling and by magnetic field measurements with a range of different members. This work has established that the shielding factor SF (that is, B0/Bs) depends on the distance from the lower end of the shield member and on the wall thickness of the body. However, the shielding factor is not significantly influenced by the permeability of the ferromagnetic material of which the body is made, at least for practical wall thicknesses for the body.
An example of magnetic flux density distribution around a cylindrical shielding member (2) is shown in Figure 2. In Figure 2, shielding member (2) is shown as sectioned through the z axis. Thus, the y-z plane is illustrated with shielding member (2) in the same orientation as shown in Figure 1. In the test from which the flux density distribution of Figure 2 was derived, the shielding member (2) was made of mild steel having a permeability μ of 4000H/m, an internal diameter of 20 mm, a wall thickness of 8 mm and a length of 20 mm. The magnetic field for which the variation in flux density is shown in Figure 2 had a strength of 400 Gauss. As is evident from Figure 2, the field strength is very substantially reduced within and outside of the shielding member (2).
As is evident from Figure 2, the strongest reduction in the magnetic field is inside the shielding member. Modelling indicates that, with variation in wall thickness of the body of the shielding member, the shielding factor at the lower end of the shielding member should increase from 4.8 at a wall thickness of 2 mm to 12.6 at a wall thickness of 16 mm. This represents a decrease in the magnetic flux density at the lower end of the shielding member, from the external value of 400 Gauss, to a level of 83.5 Gauss for the wall thickness of 2 mm and a level of 31.7 Gauss for the wall thickness of 16 mm. The examples of model predictions are shown in Table I, while Table Il provides a comparison of predicted and measured screening factors.
Table I - Screening factors predicted by modelling for a screening member in magnetic field of 400 Gauss
Figure imgf000013_0001
Table Il - Comparison of predicted screening factors by modelling and measured for a cylindrical shielding member in magnetic field of 400 Gauss
Figure imgf000014_0001
As it can be seen from Table II, there is a reasonable agreement between the predicted and measured screening factor values for shielding members of various wall thicknesses in a transverse magnetic field of 400 Gauss.
Use of the experimental shielding members has resulted in good arc starting and the completion of satisfactory bead on plate welds with a standard GMAW power source delivering either 200 A or 300 A. Similarly good quality welds were achieved with a shielding member designed for completion of fillet welds on the lap joints of 10 mm thick aluminium plates. Thus, the invention enables completion of good quality welds in areas where strong magnetic fields are present. One particular example where use of the invention is beneficial is within aluminium smelters, where strong reactions between the current in welding arcs and the magnetic field can preclude good welding with conventional procedures and equipment.
The shielding member can have various shapes including:
• cylindrical, single wall
• coaxial cylindrical multiple wall cylinders, • cylindrical with slots parallel or transverse to the external magnetic field lines
• a single ring of circular or rectangular shape
• multiple parallel rings of various diameters • coaxial rings
• cylindrical with angle cut
• U-shape with the U-arms transverse to magnetic field lines
• U-shape as above with slots at the bottom
• U-shape with angle cut for lap joints • U-shape with the geometry designed for fillet welds
• U-shape as above with additional side plates
• spring like made of various wire/rod diameter.
The shielding members shown in Figure 3 readily will be understood. Each of them except member number 4 is of circular cross-section between their top and bottom, that is between their upper and lower ends, although some show a taper to the second end. Member number 4 is shown as cut away, such as to enable deposition of a weld bead close to an upstanding ledge. The wall thickness "t", height "h" and internal diameter "d" for each of the members of Figure 3 are shown in an adjacent table.
Members Nos. 6 to 8 of Figures 4 to 6, respectively also are of overall circular cross-section. However, member No. 6 of Figure 4 is of penannular form, having a slit of width s as detailed in the adjacent table to improve arc visibility. Members Nos. 7 and 8 of Figures 5 and 6 show respective forms of cut-out enabling specific welding requirements to be accommodated. Members Nos. 1 1 to 14 of Figures 8 to 11 show further variants, with members Nos. 12 and 14 being for production of fillet welds, and member No. 13 enabling a weld bead deposit on the surface of a work-piece.
Member No. 10 of Figure 7 is of a modified cylindrical form, in being formed as a helical coil of 4.8 mm diameter rod. Member No. 10 is connectable to the nozzle of a welding torch by a projecting upper end of the rod, while the lowest loop of the rod where it would encircle the welding arc is closed. Despite the open form of the helical body above the closed lowest loop, member No. 10 can achieve a useful reduction in magnetic field strength such as to substantially prevent arc deflection.
Member No. 15 of Figure 12 is a simplified version of member No. 10. The member No. 15 simply comprises a closed loop (circle) of 4.8 mm diameter rod, from which an upstanding end of the rod enables connection to a nozzle as shown.
Figure 13 shows a manually adjustable shielding frame (shield No. 16) according to current practice, rather than a shielding member according to the present invention. The shielding frame is made up of bars which have a diameter of 32 mm and which are welded together to form a rectangular frame. At opposite longitudinal sides, the frame is provided with handles by which the frame is able to be moved manually. The frame encloses an operating area of 265 mm by 165 mm within which welding is to be conducted.
Shielding members Nos. 17, 18, 18P and 19, shown respectively in Figures 14 to 17, show further configurations for producing welds in specific situations. Members Nos. 18, 18P and 19, for example, are suitable for producing fillet welds, such as illustrated in Figure 18, or for T-joints. In each case, these members are of U-shape and are able to provide arc shielding by their opposed side flanges. Figure 18 illustrates an upright arrangement in which a fillet weld, shown in solid form is produced between overlapping plates. However, members Nos. 18 and 18P, for example, show tapered bodies which enable an electrode and arc to be presented at an acute angle to each of mutually perpendicular surfaces to be joined by a fillet weld such as in T-joints. Member No. 20 of Figure 19 is shown as having a lower end formed by oblique cuts to provide adjacent edges for contacting such surfaces and thereby present the electrode and arc in such manner for producing a fillet weld.
In further trials, lap joints with fillet welds of 10 mm leg length were produced using a DC gas metal arc welding (GMAW) process to investigate the weld formation during welding either with or without shielding in magnetic fields of various strengths. Two lap joints of 10 mm thick aluminium plates (Grade A6060) of 500 mm long were completed using a mechanised set up comprising a moving table, a fixed welding torch and pair of coils to produce magnetic field in the welding area. The welds were completed in the magnetic field of 100 Gauss with no magnetic shielding and in 400 Gauss with use of a torch magnetic shielding member according to the invention. The shielding member was in accordance with member No. 14 of Figure 1 1 , and was used to reduce the magnetic field locally in the arc area. The welds consisted of three passes to obtain a 10 mm leg length fillet welds. The weld appearances are shown in Figures 22 and 23. The welding details including the welding torch positioning were similar for both the welds as set out in Tables III and IV, respectively, in which target angle α and travel angle β are as illustrated in Figures 20 and 21.
Table
Figure imgf000018_0001
CTWD - Contact Tip to Work Distance
Table IV
Figure imgf000018_0002
* CTWD - Contact Tip to Work Distance As shown by the images of Figures 22 and 23 and the macro sections of Figures 24 and 25, the fillet welds made with a GMAW process in the magnetic field of either 100 Gauss with no magnetic shielding or 400 Gauss with the torch shield No 14 are very similar in their quality and penetration to the base plates. These indicate a good shielding efficiency of the torch shielding member of the invention used for welding in the presence of a strong magnetic field, such as 400 Gauss.
Figures 26 and 28 illustrate the magnetic flux density distribution (y-z plane) for two shielding members according to the invention which differ in that the member for Figure 26 is U-shaped, whereas the member for Figure 28 is cylindrical. The member for Figure 26 is member number 17 shown in Figure 14, which was made of steel and had a wall thickness of 8 mm, a height of 30 mm and a depth parallel to its side flanges of 24 mm. The member had a permeability μ of 4000 H/m and the distribution of Figures 26 and 27 was obtained with an external magnetic field strength of 400 Gauss. The cylindrical member for Figures 28 and 29 was of the same material and of corresponding dimensions, and the distribution of Figure 28 also was obtained with a field strength of 400 Gauss. These details are summarised in Table V which, in the lower half also details the increase in flux density with increasing distance from zero to 20 mm below the base or lower end of each of the shielding members. The details shown in the lower half of Table V are shown graphically in Figure 30 for the respective shielding members, illustrating their comparable performance. Table V
Figure imgf000020_0001
Figures 27 and 29 show a plot of magnetic flux density distribution against distance from the centre of the respective shielding members of Figures 26 and 28. Again, comparable performance of the members is evident from a comparison of Figures 27 and 29. The flux density is shown in Tesla (104 Gauss), while distance is shown in metres.
In further trials, manual welding was carried out using an AC-MIG pulse welding process to investigate the weld formation during welding in magnetic fields of 100G, 150G and 200G without shielding and in magnetic fields of 400G, 550G and 600G with torch shield No. 25 (see Figure 32). During the trials the arc length was adjusted to compensate for arc deflection resulting from increased strength of magnetic field. The welds made are shown in Figures 33 to 38. These trials show that with AC-MIG pulse welding it was possible to complete fillet welds of reasonable quality in magnetic fields of up to 200G without arc shielding, as shown in Figures 33 to 35. For comparison it may be noted that it is possible to weld without shielding in a magnetic field of only 5OG using continuous current DC-MIG welding with 200A. Therefore the use of AC-MIG pulse welding increases significantly the operating range of GMAW and also increases the flexibility of the torch shielding system, making it less sensitive to variations in distance between the bottom of the shield and the work-piece. This was proven in the manual welding trials carried out on single and multiple run fillet welds. Use of a purposefully designed shielding member according to the invention made it possible to complete single or multiple run fillet welds in magnetic fields of up to 600G as shown in Figures 36 to 38. The shielding member was in accordance with member No. 25 of Figure 32, and was used to reduce the magnetic field locally in the arc area. The welding details were similar for both sets of welds as set out in Tables Vl and VII, respectively.
Table Vl
Figure imgf000021_0001
CTWD - Contact Tip to Work Distance Table VII
Figure imgf000022_0001
CTWD - Contact Tip to Work Distance
As shown by the images of Figures 33 to 38, the fillet welds made with an AC- MIG process in the magnetic field of 100-200 Gauss with no magnetic shielding or 400-600 Gauss with the torch shield No 25 are very similar in their quality. These indicate a good shielding efficiency of the torch shielding member of the invention used for welding a strong magnetic field, such as 600 Gauss.
A further improvement to the shielding member may be achieved by ensuring that it remains electrically insulated from the work-piece. This may be achieved by inserting ceramic rods 39, 40 into the body of the shield, such that the ends of the rods protrude slightly preventing electrical contact between the work- piece and the shield during manual operation (refer Figures 39 and 40). This addition also assists in maintaining a constant spacing between the shield and work-piece. When ceramic rods are not present minor arcing may occur between the shield and the work-piece and this may interfere with free movement of the torch, particularly during manual welding with AC-MIG. Finally, it is to be understood that various other modifications and/or additions may be made without departing from the spirit or ambit of the invention as outlined herein.

Claims

1. A shielding member for shielding an electric arc from a relatively strong magnetic field, said electric arc being struck between an electrode and a work- piece, said shielding member including a main body adapted to extend at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
2. A shielding member according to claim 1 wherein said main body is formed substantially from a ferromagnetic material to locally distort said magnetic field.
3. A shielding member according to claim 1 or 2 wherein said main body is formed from a material having low electric conductivity.
4. A shielding member according to claim 1 , 2 or 3 wherein said electrode is retained in a welding torch including a gas nozzle and said shielding member is releasably securable to said gas nozzle.
5. A shielding member according to claim 1 , 2 or 3 wherein said electrode is retained in a welding torch including a gas nozzle and said shielding member is secured to said gas nozzle as a permanent attachment.
6. A shielding member according to claim 1 , 2 or 3 wherein said electrode is retained in a welding torch including a gas nozzle and said shielding member is formed in one piece with said gas nozzle.
7. A shielding member according to claim 4, 5 or 6 wherein said shielding member extends around the exterior of said gas nozzle.
8. A shielding member according to claim 4, 5 or 6 wherein said shielding member extends around the interior of said gas nozzle.
9. A shielding member according to any one of the preceding claims wherein said main body extends beyond the free end of said electrode.
10. A shielding member according to any one of the preceding claims wherein said main body is shaped such that it substantially conforms to the profile of said work-piece.
1 1. A shielding member according to any one of the preceding claims wherein said main body is substantially cylindrical.
12. A shielding member according to any one of the preceding claims wherein at its leading side said main body includes a projecting tab corresponding to the profile of a groove along a weld seam to further protect said arc.
13. A shielding member according to any one of the preceding claims wherein a surface of said work-piece is flat and the lower end of said main body is substantially planar.
14. A shielding member according to any one of claims 1 to 12 wherein a surface of said work-piece is arcuate and the lower end of said body is of complementary form.
15. A shielding member according to any one of the preceding claims wherein at its trailing side said main body includes a notch to enable said shielding member to be moved along a beadline built up on said work-piece.
16. A shielding member according to any one of claims 1 to 10 wherein said main body includes a U-shaped cross-section in planes extending perpendicular to the axis of said electrode.
17. A shielding member according to claim 16 wherein said U-shaped cross section extends through to its upper and lower ends.
18. A shielding member according to claim 16 wherein said main body includes an annular collar at its upper end and said U-shaped cross section extends through to its lower end.
19. A shielding member according to claim 16, 17 or 18 wherein a fillet weld is produced on said work-piece and said main body is adapted to be positioned closely adjacent to surfaces between which said fillet weld is to be produced.
20. A shielding member according to any one of the preceding claims wherein said main body includes side flanges, each flange including a plate adjustably mounted thereon.
21. A shielding member according to claim 20 wherein said plates are adjustable such that lateral spacing between said electrode and a surface of said work-piece can be varied.
22. A shielding member according to any one of the preceding claims wherein said main body is tapered such that it decreases in cross-section towards its lower end.
23. A shielding member according to any one of the preceding claims wherein said electric arc is produced by a direct current (DC) power source.
24. A shielding member according to claim 23 wherein said power source is pulsed DC.
25. A shielding member according to any one of claims 1 to 22 wherein said electric arc is produced by an alternating current (AC) power source.
26. 'A shielding member according to claim 25 wherein said power source is pulsed AC or includes variable polarity.
27. A shielding member according to any one of the preceding claims wherein said main body is insulated from said work-piece.
28. A method of shielding an electric arc from a relatively strong magnetic field, said electric arc being struck between an electrode and a work-piece, said method including applying a shielding member at least a major part around an end portion of said electrode to substantially shield said end portion and/or said electric arc from said magnetic field.
29. A method according to claim 28 wherein said shielding member is formed substantially from a ferromagnetic material to locally distort said magnetic field.
30. A method according to claim 28 or 29 wherein said shielding member is formed from a material having low electric conductivity.
31. A method according to claim 27, 28 or 29 wherein said electrode is retained in a welding torch including a gas nozzle and said shielding member is releasably securable to said gas nozzle.
32. A method according to claim 27, 28 or 29 wherein said electrode is retained in a welding torch including a gas nozzle and including securing said shielding member to said gas nozzle as a permanent attachment.
33. A method according to claim 27, 28 or 29 wherein said electrode is retained in a welding torch including a gas nozzle and including forming said shielding member in one piece with said gas nozzle.
34. A method according to claim 31 , 32 or 33 including extending said shielding member around the exterior of said gas nozzle.
35. A method according to claim 31 , 32 or 33 including extending said shielding member around the interior of said gas nozzle.
36. A method according to any one of claims 28 to 35 including extending said shielding member beyond the free end of said electrode.
37. A method according to any one of claims 28 to 36 including shaping said shielding member such that it substantially conforms to the profile of said work- piece.
38. A method according to any one of claims 28 to 37 wherein said shielding member is substantially cylindrical.
39. A method according to any one of claims 28 to 38 including providing said shielding member with a projecting tab at its leading side corresponding to the profile of a groove along a weld seam to further protect said arc.
40. A method according to any one of claims 28 to 39 wherein a surface of said work-piece is flat and the lower end of said shielding member is substantially planar.
41. A method according to any one of claims 28 to 39 wherein a surface of said work-piece is arcuate and the lower end of said shielding member is of complementary form.
42. A method according to any one of claims 28 to 41 including providing said shielding member with a notch at its trailing side to enable it to be moved along a beadline built up on said work-piece.
43. A method according to any one of claims 28 to 37 including providing said shielding member with a U-shaped cross-section in planes extending perpendicular to the axis of said electrode.
44. A method according to claim 43 including extending said U-shaped cross section through to its upper and lower ends.
45. A method according to claim 43 including providing said main shielding member with an annular collar at its upper end and extending said U-shaped cross section through to its lower end.
46. A method according to claim 43, 44 or 45 wherein a fillet weld is produced on said work-piece and including positioning said shielding member closely adjacent to surfaces between which said fillet weld is to be produced.
47. A method according to any one of claims 28 to 46 including providing said shielding member with side flanges, each flange including a plate adjustably mounted thereon.
48. A method according to claim 47 wherein said plates are adjustable such that lateral spacing between said electrode and a surface of said work-piece can be varied.
49. A method according to any one of claims 28 to 48 wherein said shielding member is tapered such that it decreases in cross-section towards its lower end.
50. A method according to any one of claims 28 to 49 wherein said electric arc is produced by a direct current (DC) power source.
51. A method according to claim 50 wherein said power source is pulsed DC.
52. A method according to any one of claims 28 to 49 wherein said electric arc is produced by an alternating current (AC) power source.
53. 'A method according to claim 52 wherein said power source is pulsed AC or includes variable polarity.
54. A method according to any one of claims 28 to 53 including insulating said shielding member from said work-piece.
55. A shielding member substantially as herein described with reference to figures 1 to 12 and 14 to 40 of the accompanying drawings.
56. A method of shielding an electric arc substantially as herein described with reference to figures 1 to 12 and 14 to 40 of the accompanying drawings.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009082238A3 (en) * 2007-12-21 2010-02-18 Efd Induction A.S. Electric welding of aluminium or aluminium alloy
CN110461525A (en) * 2017-03-23 2019-11-15 株式会社神户制钢所 Groove packing material dissemination apparatus and submerged arc welding apparatus
CN113543614A (en) * 2021-06-11 2021-10-22 西安空间无线电技术研究所 Large passive intermodulation shielding darkroom
EP3981535A1 (en) * 2020-10-08 2022-04-13 Linde GmbH Shield nozzles for cathodic cleaning of materials and for t-joint welding

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6261782A (en) * 1985-09-10 1987-03-18 Nippon Kokan Kk <Nkk> Electron beam welding device
JPH09206959A (en) * 1996-01-30 1997-08-12 Mitsubishi Heavy Ind Ltd Electron beam welding method between different kinds of material
FR2809644A1 (en) * 2000-05-30 2001-12-07 Renault ROBOT, ESPECIALLY ELECTRIC WELDING, WITH MOBILE MECHANICAL PART CONTROLLED BY AN ARMORED SENSOR

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6261782A (en) * 1985-09-10 1987-03-18 Nippon Kokan Kk <Nkk> Electron beam welding device
JPH09206959A (en) * 1996-01-30 1997-08-12 Mitsubishi Heavy Ind Ltd Electron beam welding method between different kinds of material
FR2809644A1 (en) * 2000-05-30 2001-12-07 Renault ROBOT, ESPECIALLY ELECTRIC WELDING, WITH MOBILE MECHANICAL PART CONTROLLED BY AN ARMORED SENSOR

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009082238A3 (en) * 2007-12-21 2010-02-18 Efd Induction A.S. Electric welding of aluminium or aluminium alloy
CN110461525A (en) * 2017-03-23 2019-11-15 株式会社神户制钢所 Groove packing material dissemination apparatus and submerged arc welding apparatus
EP3981535A1 (en) * 2020-10-08 2022-04-13 Linde GmbH Shield nozzles for cathodic cleaning of materials and for t-joint welding
WO2022073643A1 (en) * 2020-10-08 2022-04-14 Linde Gmbh Shield nozzles for cathodic cleaning of materials and for t-joint welding
CN113543614A (en) * 2021-06-11 2021-10-22 西安空间无线电技术研究所 Large passive intermodulation shielding darkroom

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