Dual-flow shielding gas arc welding torch.

Abstract

Dual-flow shielding gas arc welding torch. The invention relates to a welding torch (10), comprising: - an electrode (11) extending along a longitudinal axis (X) and intended to form an electric arc with a workpiece, the electrode comprising an internal conduit (16) opening through a free end, the internal conduit being configured to circulate and then eject a shielding gas, called internal gas, through the free end, - a nozzle (12) arranged around the electrode, preferably coaxially, the nozzle being configured to eject a shielding gas, called external gas, from the nozzle to the free end of the internal conduit of the electrode, - flow control means for ejecting an internal gas flow (Fint) of composition and / or flow rate and / or pressure independent of that(s) of the external gas ejection flow (Fext). Figure for the abridged version: fig. 5

Description

Title of the invention: Dual-flow shielding gas arc welding torch. technical field

[0001] The present invention relates to the field of gas-shielded arc welding torches, in particular TIG welding torches (Anglo-Saxon acronym for "Tungsten Inert Gas").

[0002] Gas-shielded arc welding torches cover in particular the processes of families 13 (MIG / MAG), 14 (TIG / TAG) and 15 (Plasma) of standard NF EN ISO 4063.

[0003] Although the invention is described with reference to a TIG welding application, it can be considered for any other gas-shielded arc welding process. Prior art

[0004] TIG welding processes, also called family 14 processes according to standard NF EN ISO 4063, use an electric arc between a non-consumable tungsten or tungsten alloy electrode and the workpiece to be welded to produce a weld.

[0005] Figure 1 illustrates a prior art TIG welding process implemented by a TIG welding torch 1. Such a torch 1 comprises a tungsten or tungsten alloy electrode 2 and a nozzle 3 arranged coaxially around the electrode 2. The electrode 2 produces an electric arc E between the electrode 2 and the parts 4a and 4b to be welded together. The electric arc E heats the parts 4a and 4b to be welded, creating a weld pool 5 which, after the passage of the TIG welding torch 1 and its cooling, forms the weld 6, for example, a weld bead. A protective gas flow F is ejected from the nozzle 3 towards the electric arc E. The protective gas flow F protects against oxidation of the electrode 2 and parts 4a and 4b, it also has a plasma-generating function and cools the non-fusible elements of the torch 1.

[0006] Generally, in a TIG process, material is added via a welding wire 7. In conventional TIG welding processes, the welding wire 7 is located away from the TIG welding torch 1, which complicates the handling of the torch 1 during welding. For example, in a manually performed TIG welding process, the welder must hold the TIG welding torch 1 in one hand and the welding wire 7 in the other. As another example, in a robotic TIG welding process, at least one robot must perform large movements requiring high acceleration, particularly during curved trajectories, causing wear on the robot and reducing welding accuracy.

[0007] Patent applications WO2018 / 036122 A1, CN106312270 A, CN111266702 A, and CN107186322 A each describe a TIG welding torch with a welding wire arranged and fed coaxially with the electrode. However, these TIG welding torches are particularly bulky, which complicates their use. In particular, their diameter is large near the arc generation zone. Furthermore, some of the TIG welding torches described in the aforementioned patent applications require an independent cooling system, which further increases their size and makes them difficult to handle.

[0008] There is therefore a need for a welding torch, in particular a TIG welding torch, overcoming the aforementioned disadvantages.

[0009] The object of the invention is to meet, at least in part, this need(s). Description of the invention

[0010] To this end, the invention relates to a welding torch, comprising: - an electrode extending along a longitudinal axis X and intended to form an electric arc with a workpiece to be welded, the electrode comprising an internal conduit opening through a free end, the internal conduit being configured to circulate and then eject a protective gas, called internal gas, through the free end; - a nozzle arranged around the electrode, preferably coaxially, the nozzle being configured to eject a protective gas, called external gas, out of the nozzle towards the free end of the internal conduit of the electrode; - means for ejecting an internal gas flow of composition and / or flow rate and / or pressure independent of that(s) of the external gas ejection flow.

[0011] The present invention therefore essentially consists of a welding torch adapted to eject an internal gas flow and an external gas flow, the flows being independent of each other. Advantageously, this improves the control of the shielding gas supply at the level of the electric arc emission zone. It is thus possible to precisely adjust the shape of the plasma generated by the electric arc and therefore the heat flows used during a welding process.

[0012] Advantageously, the internal and external gas flow rates can also be adjusted to avoid degradation of the welding torch, in particular the electrode.

[0013] It is also possible to supply the electric arc emission zone with an internal gas having a different composition from the composition of the external gas, each of the gas compositions having a different preferred function.

[0014] For example, one composition being particularly plasma-forming and the other composition being more protective against oxidation and / or thermally insulating. In particular, the external gas can be chosen for a function Plasmagen and the internal gas can provide chemical and thermal protection for the components of the welding torch.

[0015] Preferably, the internal gas and / or the external gas is argon. Other gases can obviously be considered.

[0016] The internal and external gas ejection flow rates are advantageously on the order of Nl / min.

[0017] Preferably, the nozzle is set back longitudinally from the electrode, the welding torch being configured so that the external gas flows while attached along the external surface of the electrode to its free end protruding out of the nozzle.

[0018] For the purposes of the present invention, a gas flow is attached along a surface when its streamlines are parallel to said surface and the gas flow remains concentrated in the immediate vicinity of said surface.

[0019] Preferably, the welding torch includes a welding wire, preferably made of metal, housed in the internal conduit, preferably coaxially, protruding beyond the free end of the electrode.

[0020] Inserting the welding wire through the internal channel of the electrode facilitates the handling of the welding torch and simplifies the movements required during a welding process using the welding torch. This makes it possible, for example, to reduce the number of movements required when a robot uses the welding torch according to the present invention. It also frees up a welder's hand during a manual welding process using the welding torch.

[0021] Preferably, the welding torch includes an electrically and thermally insulating guide tube, arranged preferably coaxially in the internal conduit of the electrode and in which the welding wire is threaded.

[0022] Preferably, the electrode is made of tungsten or tungsten alloy.

[0023] Preferably, the free end of the electrode has a surface of general shape external frustoconical shape.

[0024] Preferably, the welding torch includes an insulating structure arranged between the nozzle and the electrode so as to insulate them electrically and thermally.

[0025] The present invention also relates to the use of a welding torch according to the present invention to carry out a welding process, preferably a TIG welding process.

[0026] Preferably, the external gas and / or internal gas ejected by the welding torch during the welding process is argon.

[0027] Other gases can obviously be considered. Brief description of the drawings

[0028] Other advantages and features will become clearer upon reading the detailed description, given by way of illustration and not limitation, with reference to the following figures:

[0029] [Fig-1] Fig. 1 is a schematic perspective view of a welding torch TIG according to the prior art during a TIG welding process.

[0030] [Fig.2] Fig.2 is a perspective view of a welding torch according to the present invention, the different elements of the welding torch being represented in transparency.

[0031] [Fig. 3] Fig. 3 is a view from below of a welding torch according to the present invention.

[0032] [Fig. 4] Fig. 4 is a front view of a welding torch according to the present invention.

[0033] [Fig. 5] [Fig. 5] is a longitudinal sectional view (AA) of a welding torch according to the present invention.

[0034] [Fig.6] Fig.6 is a numerical simulation of the temperature field during a TIG welding process using a welding torch according to [Fig.1].

[0035] [Fig.7] Fig.7 is a numerical simulation of the temperature field during a TIG welding process employing a welding torch according to the present invention. Detailed description

[0036] The [Fig.1] has already been described previously and will not be described further thereafter.

[0037] Figures 2 to 5 illustrate a welding torch 10 according to the present invention. The welding torch 10 extends along a longitudinal axis X and includes a tungsten or tungsten alloy electrode 11 and a nozzle 12 arranged coaxially with the electrode.

[0038] The nozzle 12 surrounds part of the electrode 11, the other part of the electrode 11 protruding beyond the nozzle 12. In other words, the nozzle is set back longitudinally from the free end 14 of the electrode 11.

[0039] Preferably, the free end 14 protrudes from the nozzle 12 over a length L, measured along the longitudinal axis X, greater than or equal to 0.1 cm, preferably between 0.1 and 50 times the diameter d of the electrode 11.

[0040] The electrode 11 has the shape of a circular cylinder on its portion protruding from the nozzle 12. The outside diameter d of the electrode 11 can be on the order of 1mm.

[0041] The external conduit 13 delimited between the nozzle 12 and the part of the electrode 11 is configured to eject a protective gas, called external gas.

[0042] The nozzle 12 is configured so that the external gas exits the external conduit 13 flows along the longitudinal axis X while attached to the external surface of electrode 11 until its protruding free end 14.

[0043] Figure 5 illustrates the external gas flow Fext flowing into the external conduit 13 and then along the electrode 11.

[0044] The external conduit 13 has an opening diameter at the outlet of the nozzle 12 through which the electrode 11 protrudes. This opening diameter is constant over an outlet portion 13a of the external conduit 13. Upstream of the outlet portion 13a, according to the direction of the flow Fext of the external gas, the opening diameter of the external conduit 13 widens up to an inlet portion 13b.

[0045] The outer diameter of the nozzle 12 gradually widens as it moves away from said outlet along the longitudinal axis X until it reaches an outer diameter. The portion of the nozzle 12 along which its outer diameter widens.

[0046] The welding torch 10 includes an insulating structure 15 arranged between the nozzle 12 and the electrode 11, particularly in the inlet portion 13b of the external conduit 13. The insulating structure 15 is made of an electrically and thermally insulating material, for example, ceramic. In addition to electrically and thermally insulating the electrode 11 from the nozzle 12, the insulating structure 15 can mechanically maintain the coaxiality of the electrode 11 with respect to the nozzle 12.

[0047] The electrode 11 is hollow with its free end 14 open, thus forming an internal channel 16 through which a protective gas, called the internal gas, is intended to be ejected. The diameter of the opening of the internal channel 16 is between the diameter of the wire and the internal diameter of the electrode.

[0048] Figure 5 illustrates the Fint flow of the internal gas flowing inside and then out of the internal conduit 16.

[0049] The external gas supply in the external conduit 13 is independent of the internal gas supply in the internal conduit 16. Thus, the flow rates of the external and internal gases can be set differently from each other, particularly to adjust the shape of the plasma generated by the electric arc during a welding process. The composition of the external gas can be different from the composition of the internal gas. For example, the external gas can be argon and the internal gas can be helium, or vice versa.

[0050] The internal conduit 16 also forms a passage for a welding wire 17. The welding wire 17 can be inserted along the longitudinal axis X, in particular coaxially with the electrode 11, from the portion of the electrode 11 housed in the nozzle 12 until it protrudes beyond the free end 14 of the electrode 11. The welding wire 17 supplies material to the emission zone of the electric arc 18. Since the welding wire 17 is housed in the electrode 11, the movement of the welding wire 17 is intrinsically linked to that of the torch 10 in directions orthogonal to the longitudinal axis X. This greatly simplifies the handling of the torch. welding 10 during a weld requiring the addition of material. This addition of material is achieved by sliding the welding wire 17 along the longitudinal axis X.

[0051] The welding torch 10 includes a guide tube 19 arranged in the internal conduit 16 extending to the free end 14 of the electrode 11. The guide tube 19 is coaxial with the electrode 11 along the longitudinal axis X. The welding wire 17 is threaded into the guide tube 19, which ensures the mechanical retention and centering of the welding wire 17 in the internal conduit 16 and guides the welding wire 17 during its insertion into the electrode 11.

[0052] The guide tube 19 is made of an electrically and thermally insulating material, for example ceramic, which allows the welding wire 17 to be electrically and thermally insulated from the electrode 11 during the welding process.

[0053] Furthermore, the free end 14 protruding from the electrode 11 is a surface of generally external frustoconical shape whose apex forms the tip of the electrode 11.

[0054] The inventors carried out multiphysics numerical simulations, using the software marketed under the name "Cast3M", in order to compare a welding torch 1 according to the state of the art, as illustrated in [Fig.1], to a welding torch 10 according to the present invention.

[0055] The external gas flow is imposed on the gas inlet surface with the same opening diameter.

[0056] Figures 6 and 7 respectively illustrate the thermal field 20 and 21 obtained by a simulation of the use of the welding torch 1 according to the prior art and the welding torch 10 according to the present invention.

[0057] For these simulations, the arc height, i.e., the distance between the free end 24 or 14 of the electrode 2 or 11 and the workpiece 4, was 10 mm. The simulation for the welding torch 1 according to the prior art was carried out with a shielding gas flow F ejected at a rate of 22.5 Nl / min, the shielding gas being argon. The simulation for the welding torch 10 according to the present invention was carried out with an external gas flow Fext ejected at a rate of 22.5 Nl / min and an internal gas flow Fint ejected at a rate of 1.5 Nl / min, the external gas being argon, the internal gas being argon.

[0058] These simulations show that the temperature at the free end 24 of the electrode 2 of the welding torch 1 according to the prior art is 18000 K whereas it is only 10900 K for the free end 14 of the electrode 11 of the welding torch 10 according to the present invention.

[0059] Furthermore, these simulations show better control of heat flow when using the welding torch 10 according to the present invention, the temperature being more homogeneous between the workpiece 4 and the electrode 11.

[0060] Other variants and improvements may be envisaged without departing from the scope of the invention.

Claims

Demands

1. A welding torch (10) comprising: - an electrode (11) extending along a longitudinal axis (X) and intended to form an electric arc with a workpiece, the electrode comprising an internal conduit (16) opening at a free end, the internal conduit being configured to circulate and then eject a shielding gas, referred to as the internal gas, through the free end, - a nozzle (12) arranged around the electrode, preferably coaxially, the nozzle being configured to eject a shielding gas, referred to as the external gas, from the nozzle to the free end of the internal conduit of the electrode, - flow control means for ejecting an internal gas flow (Fint) of composition and / or flow rate and / or pressure independent of that(s) of the external gas ejection flow (Fext), - an insulating structure (15) arranged between the nozzle and the electrode so as to insulate them electrically and thermally.

2. Welding torch according to claim 1, the nozzle being set back longitudinally from the electrode, the welding torch being configured so that the external gas flows while attached along the external surface of the electrode to its free end protruding out of the nozzle.

3. Welding torch according to any one of the preceding claims, comprising a welding wire (17), preferably of metal, housed in the internal conduit (16), preferably coaxially, protruding beyond the free end of the electrode.

4. Welding torch according to claim 5, comprising an electrically and thermally insulating guide tube (19), arranged preferably coaxially in the internal conduit of the electrode and in which the welding wire is threaded.

5. Welding torch according to any one of the preceding claims, the electrode being made of tungsten or tungsten alloy.

6. Welding torch according to any one of the preceding claims, the free end of the electrode having a surface of generally frustoconical external shape.

7. Use of a welding torch (10) according to one of the preceding claims to carry out a welding process, preferably a TIG welding process.

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