FR2805766A1 - Electric arc welding torch with two protective gas flows for TIG, MIG and MAG welding comprises concentric first protective gas flow central distribution nozzle and a peripheral part forming a sleeve for a second protective gas flow - Google Patents

Abstract

Arc welding torch for TIG, MIG and MAG welding comprises a first protective gas flow central distribution nozzle (1) of thickness (e) 3-6 mm, and a peripheral part (2) forming a sleeve and permitting the distribution of a second gas flow peripheral to the first gas flow. The central distribution nozzle (1) and the peripheral part (2) are concentric. Preferred Features: The downstream end (2') of the peripheral part (2) is set back from the downstream end of the central distribution nozzle (1) by 1 mm, preferably 2-15 mm, more preferably 5-10 mm. The peripheral part (2) forming the sleeve is more or less cylindrical or truncated cylindrical in shape. The distance separating the surface of the internal wall of the peripheral part from the surface of the external wall of the nozzle (1) is at least 1 mm, preferably 2-10 mm. The torch also includes and an electrode (10) and/or at least one consumable wire, and a holder for the electrode or the wire.

Description

The present invention relates to a torch for welding the electric arc, in particular of TIG (Tungsten Inert Gas), MIG (Metal Inert Gas) or MAG (Metal Active Gas) type, with double-flow of gas protection intended to protect the zone of welding during the welding operation.

Gaseous shielded arc welding processes are widely used in industry.

In a schematic way, using a gas shield, during a welding operation, makes it possible to avoid contamination of the weld bead thus produced from any contamination by impurities that may be present in the ambient atmospheric air.

Indeed, it is known that, in particular nitrogen and oxygen contained in the ambient air are harmful the quality of the weld seams, which undergo a deterioration of their appearance due to oxidation and nitriding phenomena, and their integrity, that is to say, their characteristics of strength and mechanical performance.

The establishment of a gas shield during the arc welding operation is therefore intended to avoid or minimize any contamination of the weld bead by said atmospheric impurities.

However, it is known that the gas shield is not neutral with respect to the welding results thus obtained and in particular influences the welding speed, the penetration, the shape of the weld bead, the amount of smoke released during the welding. welding and the number more or less important projections of molten metal.

In other words, the physicochemical properties of the gases or gaseous mixtures used as the shielding gas cause differences in the behavior of the electric arc, the molten metal bath and, in the case of a MIG welding, fusing the fusible wire, leading to very variable welding results depending on the type of gas used; In general, in the protective gaseous flow, also called gas shielding atmosphere, there are two main areas, namely the arc zone and the actual protection zone.

More specifically, the first zone or arc zone comprises the electric arc itself, the portion of the welding bath located substantially below the electric arc and the end of the welding electrode or fuse wire is near the welding bath.

In addition, the second zone or protection zone includes the remainder of the gas flow, that is to say, zone substantially peripheral to the arc zone, in which the action of the gas shield is substantially limited to a protection of the weld seam.

Depending on the case, the gas or the gaseous mixture is identical or different in these two zones, for example it is known to use carbon dioxide (CO 2) gas distributed indifferently in the arc zone and in the protection zone proper.

When it is desired to distribute two gases of different natures or compositions in the central arc zone and in the peripheral protection zone, it is usual to use a so-called "double flux" welding torch.

A dual flux welding torch usually consists of a torch body provided with two concentric nozzles, namely a central gas distribution nozzle for delivering a first gas stream into the arc zone, and a peripheral sleeve piece. external device arranged around at least a portion of the central distribution nozzle and for distributing a second gaseous flow peripherally to said first gas flow, that is to say in the protection zone.

Such torches are described in particular in the following documents: GB-A-2059846 and US-A-2,919,341.

in practice, it was found that with this type of torch was the problem of controlling the gas mixture at the arc zone, because indeed, no precautions are taken, it is very difficult to have in the arc zone a mixture whose content of gas flowing in the outer nozzle is low and in particular in the presence of a flow of gas flowing in the weak inner nozzle.

Indeed, the only way to measure the mixture is to act on the flow rates flowing in each of the nozzles - if the flow rate of the external gas is too high, then a gas mixture is obtained in the arc zone with a high proportion of external gas; - if you try to reduce it, then very quickly the external gas flow is too low and the weld is poorly protected.

The object of the present invention is therefore to solve the aforementioned problem by providing an improved dual-flux welding torch compared to existing torches, that is to say that allows to have a gas mixture in the arc zone low in external gas while having a low internal gas flow rate.

The inventors of the present invention have now shown that the above-mentioned problem can be solved or minimized by a double flux welding torch. The invention thus relates to an arc welding torch comprising - a central gas distribution nozzle for delivering a first gas stream, and - an outer sleeve peripheral piece arranged around at least a part of said gas nozzle. central distribution and for distributing a second gaseous flow peripherally to said first gas, characterized in that the thickness (e) of the central nozzle is between 3 and 6 mm.

Indeed, as detailed below, the inventors of the present invention have demonstrated that the thickness (e) has a significant influence on the control efficiency of the gas mixture in the arc zone.

Depending on the case, the torch of the invention may comprise one or more of the following characteristics - the downstream end of the peripheral piece is set back (Ê) at least 1 mm from the downstream end of the nozzle central distribution.

distance (d) is at least 1 mm and preferably between 2 and 10 mm.

distance (d) is between 2 mm and 9, preferably between 3 mm and 5 mm.

- The downstream end of the peripheral piece is withdrawal (@) of 2 to 15 mm with respect to the downstream end of the central distribution nozzle, preferably mm to 10 - peripheral sleeve piece has a substantially cylindrical or cylindrical shape truncated.

- Central gas distribution nozzle peripheral piece forming outer sleeve arranged around said central distribution nozzle are concentric. - It further comprises at least one electrode and / or at least one fusible wire, power supply means connected to said electrode or said fuse wire, and means for holding said electrode or said fuse wire.

it is chosen from TIG, MIG or MAG torches.

The invention will now be described in more detail with the help of the appended figures, given by way of illustration but not limitation.

Figures 1, 2a, 2b, 3 and 5 show partial diagrams of welding torches according to the invention, that is to say showing the active end of the torch comprising the two concentric gas distribution nozzles.

As shown in FIG. 1, the double-flux type torch is provided with a central contact tube 3 intended to carry an electrode 10 or a fuse wire. A central distribution nozzle 1 is arranged peripherally to the contact tube 3 and is connected to means for supplying a first gas (G1) for distributing this first gas (G1) in the arc zone ZA.

Another nozzle or peripheral piece 2 forms an outer sleeve around a portion of the dispensing nozzle 1; the peripheral part 2 and the central distribution nozzle 1 being concentric.

The peripheral part 2 is, moreover, connected to means for supplying a second gas G2 intended to be distributed in at least part of the protection zone ZP.

In FIG. 5, it can be seen that the arc zone ZA which contains the electric arc AE is located substantially between the electrode 10 and the weld S carried by the material M to be welded, whereas the protection zone ZP is located substantially around said arc area ZA. According to the invention, the thickness (e) of the central nozzle is between 2 and 10 mm, preferably between 3 and 6 mm.

In addition, the distance (d) separating the surface of the inner wall from the peripheral part 2 from the surface of the outer wall of the central nozzle 1 is at least 1 mm, preferably from 2 to 10 mm.

Finally, it is preferable that the end 2 'of the peripheral piece 2 is recessed (2) by at least about 1 mm, and preferably from 5 mm to 10 mm, with respect to the end 1' of the nozzle. distribution 1.

Indeed, the inventors of the present invention have demonstrated that the thickness (e) of the central nozzle controlled, to a very large extent the amount of external gas in the arc zone. The greater this distance, the lower the external gas concentration in the arc zone, especially for low internal gas flow rates.

Likewise, the inventors of the present invention have demonstrated that the distance (d) and / or the shrinkage (#) have a significant influence on the quality of the gas protection of the weld seam and this, even if thickness (e) of the inner nozzle is correctly sized.

indeed, if the distance (d) is too small, which is naturally sought for reasons of flow minimization, the outside air arrives to return to the level of the welding bath, and thus induces protection defects such as for example porosities. Likewise, when this distance (d) is suitably selected, it may happen that welding projections reduce the apparent length thereby causing the same defect of gas protection. Also, it is preferable to introduce a length recess (2) so that the welding projections, which generally come from the arc zone, can not adhere to the inner surface of the outer nozzle, and can not thus do not cause premature closure of the external gas duct.

In order to evaluate the influence of the thickness (e) on the contents of the mixture in the arc zone, said thickness (e) is varied all things being equal, and the gas concentration G 2 is then determined in the arc zone, 10 mm below the nozzle.

In all tests, the gases G1 and G2 are different and are chosen from argon, helium, carbon dioxide, oxygen, hydrogen and their mixtures.

To do this, a welding nozzle similar to that of FIG. 1 is used, for which el = 1.25 mm approximately and e2 = d = 3.5 mm approximately (e1 and e2 being kept constant).

In addition, the gas flow G1 is <B> 2.5 </ B> 1. min-1 and the gas flow G2 is 15 l.min-1.

The results obtained are shown in FIG. 4 where it can be seen that, the greater the thickness (e) (represented on the x-axis by the distance between the two streams), the greater the proportion of G2 in the G1 mixture. / G2 realized in situ in the arc area decreases.

It follows that it is desirable to obtain a suitable mixture G1 / G2, that the thickness (e) is at least 1 mm, or even at least 2 mm and in all cases less than 10 mm. mm. Preferably, the thickness (e) is between about 3 and about 6 mm.

The torch of the invention is particularly suitable for use in a TIG, MIG or MAG welding operation.

Claims (2)

claims An electric arc welding torch comprising: a central gas distribution nozzle (1) for delivering a first gas stream; an outer sleeve forming part (2) arranged around at least a part of said nozzle of central distribution (1) and for distributing a second gaseous flow peripherally to said first gaseous flow, characterized in that the thickness (e) of the central nozzle is between 3 and 6 mm. 2. Torch according to claim 1, characterized in that the downstream end (2 ') of the peripheral piece (2) is recessed (.) At least 1 mm from the downstream end (1'). of the central distribution nozzle <B> M - </ B> <B> 3. </ B> Torch according to one of claims 1 or 2, characterized in that the distance (d) is at least 1 mm and preferably between 2 10 mm. 4. Torch according to one of claims 1 to 3, characterized in that the distance is between 2 mm and 9 mm, preferably between 3 mm and 5 mm. 5. Torch according to one of claims 1 to 4, characterized in that the downstream end (2 ') of the peripheral piece (2) is recessed (#) from 2 to 15 mm with respect to the downstream end (1 ') of the central distribution nozzle (1), preferably from 5 mm to 10 mm. 6. Torch according to one of claims 1 to 5, characterized in that the peripheral piece forming sleeve (2) has a substantially cylindrical or cylindro-frustoconical shape. 7. Torch according to one of claims 1 to 6, characterized in that the central distribution nozzle (1) and the outer sleeve forming part (2 external arranged around said central distribution nozzle) are concentric. 8. Torch according to one of claims 1 to 7 characterized in that it further comprises at least one electrode (10) and / or at least one fusible wire, means imentation electric current connected to said electrode (10) or said fuse wire, and holding means (3) of said electrode (10) or said fuse 9. Torch according to one of claims 1 to characterized in that it is selected from TIG torches, or MAG. 10 Use of a torch according to one of claims 1 to 9 in a MIG or MAG TIG welding operation.