Method and device for welding workpieces in protective gas chamber

Abstract

The invention relates to a method and a device (1) for welding a workpiece (W) in a shielding gas chamber (2), comprising a shielding gas chamber (2) having a line (3) for the inflow of a shielding gas (G), and comprising a welding torch (4) for carrying out a welding process when a fusible welding wire (5) is supplied, the welding torch (4) having a gas channel (6) for supplying the shielding gas (G). The aim of the invention is to prevent the accumulation of metal dust generated during the welding process and to achieve the welding quality as good as possible and to reduce the risk of ignition or explosion due to unoxidized dust. According to the invention, the welding torch (4) is designed to draw the shielding gas chamber atmosphere (L) from the welding point (S) through the gas channel (6) at least during the welding process, wherein the direction of the gas flow in the gas channel (6) is at least temporarily reversed.

Description

Field of the Invention

[0001] The present invention relates to a method for welding a workpiece in a protective gas chamber, wherein the protective gas chamber is filled with a protective gas through a corresponding line before the start of the welding process, and the workpiece is welded using a welding torch including a gas pipe for supplying the protective gas and a fusible wire that can be supplied to the welding position.

[0002] The present invention also relates to a device for welding a workpiece in a protective gas chamber, including a protective gas chamber having a line for flowing in a protective gas, and a welding torch including for carrying out the welding process when supplying a fusible wire, wherein the welding torch has a gas passage for supplying the protective gas. Background Art

[0003] The present invention generally relates to welding workpieces in a protective gas chamber, in particular to the surfacing and additive manufacturing of shaped bodies made of metal, for example, which are known under the terms "wire arc additive manufacturing (WAAM)" and "arc directed energy deposition (Arc-DED)". In the additive manufacturing of shaped bodies made of non-ferrous metals having an affinity for oxygen, it is particularly important to protect the workpiece from oxygen to avoid oxidation. In particular, titanium and nickel and their alloys oxidize very strongly, which is why the welding process must be carried out under a protective gas atmosphere until the material drops below the critical temperature, at which harmful oxidation occurs. For example, argon is used as the protective gas in the protective gas chamber, and it is also often used as the protective gas during the welding process to protect the arc. Welding in a protective gas chamber is very complex, and due to the large chamber volume and the requirement for a low oxygen concentration, a very high consumption of protective gas is required. On the one hand, in order to maintain a low oxygen concentration in the protective gas chamber despite leaks, and on the other hand, in order to eliminate the contamination of the protective gas chamber due to the welding process (fumes), a largely permanently clean protective gas must be supplied. In addition, welding larger workpieces (such as aircraft components made of titanium) in a protective gas chamber is associated with particularly high costs because a large amount of protective gas is required for inert filling, which cannot be used again after the welding process is completed.

[0004] The metal dust (so-called fumes) generated in the protective gas chamber during welding deposits on surfaces, such as inside the protective gas chamber and on the workpiece. During the welding process, the fumes continuously accumulate in the protective gas chamber and cause contamination of the protective gas chamber and the workpiece or structure in the weld. In addition, this metal dust is particularly dangerous because it is not oxidized and can easily burn or explode. If the protective gas is suctioned, filtered and preferably returned to the protective gas chamber, the unoxidized dust deposits in the filter and poses a significant fire or explosion hazard.

[0005] For example, DE 10 2015 108 131 A1 describes a method and a device for producing in particular metal shaped bodies by an additive manufacturing method, in which a metallic starting material is melted by means of an electric arc in a protective gas chamber and applied layer by layer.

[0006] US 6 380 515 B1 describes a welding torch which, in addition to a gas channel for supplying a protective gas to the welding location, has a suction channel through which fumes are sucked from the welding location. However, the construction of the welding torch is rather complex.

[0007] The object of the present invention is to provide the above-mentioned method and the above-mentioned device for welding workpieces in a protective gas chamber, in which metal dust (fumes) which accumulates in the protective gas chamber during the welding process and is deposited on the surface is avoided or reduced, so as to result in the highest possible quality of the produced workpieces, and there is no danger of ignition or explosion caused by non-oxidized dust inside the protective gas chamber. The consumption of the protective gas should be minimized so that the associated costs can be reduced. The method and the device should be implemented or constructed as simply and cost-effectively as possible. The disadvantages of known methods and known devices should be avoided or at least reduced. Summary of the Invention

[0008] In terms of the method, the object of the present invention is achieved as follows: at least during the welding process, the flow direction of the shielding gas in the gas passage of the welding torch is at least temporarily reversed, so that the shielding gas chamber atmosphere is sucked from the welding position. In the method according to the present invention, the function of a conventional welding torch is at least temporarily reversed, and the shielding gas chamber atmosphere is sucked from the welding position through the gas passage of the welding torch. In this conventional welding torch, the shielding gas is usually conveyed through the hose assembly and the gas passage towards the workpiece. At least during the welding process, the flow direction of the shielding gas or the shielding gas chamber atmosphere in the gas passage of the welding torch is thus at least temporarily reversed, that is, the shielding gas chamber atmosphere is actively sucked from the welding position outside the shielding gas chamber, and is transmitted along the gas passage and further along the hose assembly outside the welding system. The sucked shielding gas chamber atmosphere is understood to mean the gas in the area of the welding position, which gas contains the shielding gas and the generated fumes. Through the welding torch, the fumes are sucked directly at the formation point, and in fact there is no pollution inside the shielding gas chamber. Due to the purposeful at least temporary suction from the welding position, only a small amount of the shielding gas chamber atmosphere has to be sucked, whereby the consumption of the shielding gas can be reduced, and thus the production cost can be lowered. At the outlet of the welding system, the sucked shielding gas chamber atmosphere is mixed with the ambient air, so that any unoxidized metal particles and / or compounds contained therein are oxidized in a controlled manner, and thus no explosive dust is generated. Since the welding process is carried out in a welding chamber, which is in any case filled with shielding gas through the shielding gas supply, the flow direction in the gas passage of the welding torch can simply be at least temporarily reversed, and the supply of shielding gas to the welding position through the gas passage of the welding torch can be omitted at least temporarily. The method is characterized by being particularly simple, because a conventional or slightly adjusted welding torch can be used, and only a device for at least temporarily reversing the flow direction in the gas passage of the welding torch needs to be provided. In addition, the shielding gas can be saved, and thus the cost can be reduced and the environment can be protected.

[0009] The term "during the welding process" naturally also includes the stage before the welding process or before the arc is ignited, as well as the stage after the welding process and any intervals between the individual welding process stages. The expression that the flow direction is at least temporarily reversed during the welding process is intended to express the fact that the shielding gas chamber atmosphere can also be sucked from the welding position or even permanently sucked during the time period before or after the welding process.

[0010] The addition that the gas flow direction is "at least temporarily" reversed is intended to express the fact that the atmosphere of the shielding gas chamber is not sucked during the various stages of the welding process. In particular, during the arc stage, the reversal of the gas flow direction and the suction of the atmosphere of the shielding gas chamber would be disadvantageous because turbulent air can reach the arc due to this.

[0011] If the shielding gas chamber is filled with shielding gas before the start of the welding process, a negative pressure can be generated in the shielding gas chamber by sucking the atmosphere of the shielding gas chamber through the gas passage and emptying the shielding gas chamber through the torch, and the subsequent introduction of the shielding gas can be promoted because then less oxygen has to be transported out of the shielding gas chamber with the shielding gas. If there is still shielding gas residue in the shielding gas chamber, usually, the sucked atmosphere of the shielding gas chamber will be air or a gas mixture.

[0012] The atmosphere of the shielding gas chamber is preferably sucked through the gas passage of the torch during the welding process at a volume flow rate of 5 to 100 l / min, preferably at a volume flow rate of 15 l / min. This volume flow rate has proven to be suitable. To be able to achieve this volume flow rate, the gas passages in the torch and the subsequent hose assembly must have a suitable cross-section, for example 3 mm 2 to 150 mm 2 . The actually used cross-section usually depends on the operating pressure of the welding chamber.

[0013] Before the welding process (where the atmosphere of the shielding gas chamber is usually air), the atmosphere of the shielding gas chamber is preferably sucked from the shielding gas chamber through the gas passage of the torch at a volume flow rate of 5 to 5000 l / min. To prepare the shielding gas chamber for the welding process as quickly as possible, it is desirable to suck the atmosphere of the shielding gas chamber as quickly as possible. If this is not possible through the torch, the atmosphere of the shielding gas chamber can of course also be sucked from the shielding gas chamber through other lines.

[0014] According to another feature of the invention, during the welding process, the atmosphere of the shielding gas chamber sucked through the gas passage of the torch is filtered. Thus, the metal dust can be separated and processed in a targeted manner. Known filtration schemes for welding fume extraction can be used to filter the metal dust.

[0015] It is also advantageous if, during the welding process, the atmosphere of the protective gas chamber from which the gas passage through the torch is aspirated is cooled. Due to the fact that the arc generates very high temperatures at the welding location, the torch and following components, such as the hose assembly, any filters, etc., can be protected by cooling. The cooling can be achieved by air cooling and liquid cooling and is preferably carried out in the torch or the torch body, ensuring that the aspirated atmosphere of the protective gas chamber is reduced to below the critical temperature that can damage the components of the welding system. For example, due to the inadmissible high temperature of the aspirated atmosphere of the protective gas chamber, the mechanical strength of the plastic hoses in the hose assembly can be lost.

[0016] If oxygen is supplied to the aspirated atmosphere of the protective gas chamber through the gas passage of the torch during the welding process, oxidation of any flammable or explosive metal dust contained in the aspirated atmosphere of the protective gas chamber can be caused. Controlled oxidation can thus reduce the risk of fire or explosion. The supply of oxygen is typically carried out by supplying or mixing ambient air that contains oxygen. If the aspirated atmosphere of the protective gas chamber is filtered, the oxygen is preferably supplied upstream of the filter in order to oxidize the metal particles before the filter.

[0017] In this case, it is advantageous if, during the welding process, the aspirated atmosphere of the protective gas chamber and the supplied oxygen or ambient air are mixed or swirled through the gas passage of the torch in order to achieve optimal oxidation of the dust.

[0018] If the oxygen concentration in the protective gas chamber is measured, the welding process or the protective gas supply can be controlled or adjusted based on the measured oxygen concentration in the protective gas chamber. The oxygen content or residual oxygen in the protective gas chamber can also be determined by a plurality of suitably arranged sensors.

[0019] The flue gas content or the smoke concentration in the protective gas chamber can also be measured with a suitable sensor, such as a particulate sensor, and the welding process can be controlled or adjusted based on the measured smoke concentration in the protective gas chamber.

[0020] Furthermore, in order to be able to reliably determine the overpressure or underpressure in the protective gas chamber and to be able to control or adjust the welding process based on the pressure difference, the pressure difference between the protective gas chamber and the environment can be measured. During an active arc, a lower overpressure of at least a few millibars is intended in the protective gas chamber.

[0021] Advantageously, the welding process only starts when the oxygen concentration in the protective gas chamber is less than 100 ppm and / or the pressure difference is greater than 3 mbar. If the protective gas chamber is operated with a certain overpressure, it can be ensured that there is no ambient air and thus no oxygen entering the protective gas chamber during the welding process and that oxidation of the welding location there can be caused. In order to keep the load on the protective gas chamber and the seals of the protective gas chamber as low as possible, the overpressure should not be too high and should be significantly lower than 3 mbar.

[0022] If the amount or flow rate of the protective gas supplied to the protective gas chamber through the line is adjusted according to the measured oxygen concentration and / or the measured flue gas content and / or the measured pressure difference, the consumption of the protective gas can be adjusted according to the actual situation, and the cost of the rather expensive protective gas can be saved.

[0023] The protective gas is preferably supplied to the protective gas chamber through a plurality of lines and a plurality of inlets, so that the protective gas chamber can be filled very quickly with the protective gas. A uniform gas flow in the direction of the torch can also be achieved through a plurality of air inlets. In order to prevent or reduce eddy currents and not exert too much stress on the seals of the protective gas chamber, the inflow velocity can be very low. The number of lines and their cross-sections are adjusted accordingly according to the size of the protective gas chamber.

[0024] Before the start of the welding process, the protective gas is supplied to the protective gas chamber at a volume flow rate preferably of 5 to 5000 l / min. The aim is to fill the protective gas chamber with the protective gas as quickly as possible with the existing lines before the welding process.

[0025] Once an overpressure of preferably 1 mbar to 3 mbar relative to the environment is reached in the protective gas chamber, the supply of the protective gas to the protective gas chamber can be stopped before the start of the welding process. The lower overpressure ensures that there is sufficient protective gas in the protective gas chamber. This can prevent waste of the expensive protective gas.

[0026] If, after the welding process or after the workpiece has been completed, the shielding gas chamber atmosphere is pumped from the shielding gas chamber into a storage chamber, the shielding gas that can be reused in terms of its purity can be stored for subsequent welding processes, and thus shielding gas can be saved. Additionally, any pressure fluctuations in the shielding gas chamber can be compensated for by the storage chamber. Such pressure fluctuations can occur, for example, during the movement of a robot used to manipulate the torch or the workpiece. This happens, for example, when the robot is fixedly connected to a flexible shielding gas chamber housing and thus transfers its movement to the shielding gas chamber housing. By compensating for or minimizing the pressure fluctuations in the shielding gas chamber, even smaller forces act on the robot. During the welding process, after the contaminated shielding gas chamber atmosphere around the welding position has been suctioned off, the shielding gas remaining in the shielding gas chamber is substantially clean and can thus be reused. Pumping the shielding gas out of the shielding gas chamber creates a negative pressure that the shielding gas must compensate for before the workpiece is removed from the shielding gas chamber. The simplest way to do this is to fill it with ambient air. After the next workpiece has been inserted into the shielding gas chamber or before the next welding process begins, the shielding gas chamber atmosphere is evacuated or suctioned out of the shielding gas chamber, and then the shielding gas is conveyed into the welding chamber.

[0027] The object according to the invention can also be achieved by the above-described device for welding a workpiece in a shielding gas chamber, wherein the torch is designed to suction the shielding gas chamber atmosphere from the welding position through the gas channel at least during the welding process, and wherein the air flow direction in the gas channel is reversed at least temporarily. Regarding the advantages that can thus be achieved, reference is made to the description of the above method.

[0028] Advantageously, the cross-section of the gas channel for suctioning the shielding gas chamber atmosphere from the welding position is 3 mm 2 to 150 mm 2 . This gas channel cross-section can be achieved by a diameter of the gas channel of 2 mm to 14 mm and ensures that the shielding gas chamber atmosphere and the metal dust contained therein are suctioned off from the welding position quickly and effectively enough. The selection of a suitable cross-section of the gas channel in turn depends on the operating pressure or pressure difference in the shielding gas chamber.

[0029] If a gas nozzle with a tapered opening is arranged in front of the opening of the gas channel, optimization of the air flow of the suctioned shielding gas chamber atmosphere can be achieved. This makes it possible to ensure optimal suction of the shielding gas chamber atmosphere and the dust contained therein in the region of the welding position and to ensure that no contaminated shielding gas can escape to the interior of the shielding gas chamber at a point below the gas nozzle of the torch.

[0030] According to another feature of the present invention, a filter is arranged in the gas passage. As described above, this enables the metal dust to be optimally collected and processed.

[0031] If a baffle is provided on the torch, preferably on the gas nozzle of the torch, a laminar flow of the suctioned protective gas chamber atmosphere can be achieved in the area around the welding position. By appropriately designing the baffle, a flow field that basically only points in the direction of the arc is generated.

[0032] Furthermore, in order to achieve the targeted oxidation of the metal dust, a feed line for oxygen can be arranged in the gas passage. When a filter is also arranged in the gas passage, it is desirable that the oxygen supply and thus the oxidation of the dust occur upstream of the filter. In the simplest case, the feed line for oxygen will be achieved by supplying ambient air.

[0033] In this case, in order to achieve the optimal oxidation of the metal dust, a device for mixing or swirling the suctioned protective gas chamber atmosphere with the supplied oxygen can be provided. The mixing device can be formed by, for example, a correspondingly designed constriction, etc.

[0034] In order to achieve as uniform an air flow as possible in the gas passage, elements for guiding the air flow of the suctioned protective gas chamber atmosphere can be arranged in the gas passage and on the gas nozzle. The element can be formed by a lamellar component, etc.

[0035] In order to protect the components of the welding device from unacceptable high temperatures and prevent damage to them, a cooling device is preferably provided in the area of the gas passage. For example, it is advantageous to cool the suctioned protective gas chamber atmosphere to below 70 °C so that the components of the welding device are not damaged. In order to cool the suctioned protective gas chamber atmosphere as quickly as possible, the cooling device can be formed by air cooling and / or liquid cooling, which is preferably arranged as close as possible to the welding position. For example, the water cooling system contained in the torch with a corresponding arrangement of heat sinks for heat dissipation in any case can be used for this purpose.

[0036] A sensor for measuring the oxygen concentration and / or a particulate sensor for measuring the flue gas content or the smoke concentration and / or a differential pressure sensor for measuring the differential pressure between the protective gas chamber and the environment can be provided in the protective gas chamber. The measured values of the oxygen concentration, the flue gas content, and the differential pressure can be used to control or regulate the welding process or the protective gas chamber atmosphere. For this purpose, the sensors are connected to the control device of the welding power source.

[0037] According to another feature of the present invention, the storage chamber is connected to the protective gas chamber via a pump and a pressure equalization line having an integrated stop valve. After the welding process, the atmosphere of the protective gas chamber can be pumped out of the protective gas chamber by the pump (wherein the stop valve is closed) and stored in the storage chamber for later use. If necessary, the stored protective gas can be supplied to the protective gas chamber via the pressure equalization line and the open stop valve. In addition to its own storage chamber, the atmosphere of the protective gas chamber can also be pumped back into the existing storage tank of the protective gas. Description of the Drawings

[0038] The present invention will be explained in detail with reference to the accompanying drawings. The drawings show:

[0039] Figure 1 A schematic view of a device for welding a workpiece in a protective gas chamber according to the prior art;

[0040] Figure 2 A schematic view of a device for welding a workpiece in a protective gas chamber using the method according to the present invention, wherein the air flow direction in the gas channel is reversed;

[0041] Figure 3 A preferred embodiment of a welding torch suitable for implementing the welding method according to the present invention;

[0042] Figure 4 Another preferred embodiment of a welding torch suitable for implementing the welding method according to the present invention; and

[0043] Figure 5 A cooling device for cooling the welding torch or the aspirated protective gas chamber atmosphere through the gas channel of the welding torch during the welding process. Detailed Description of the Invention

[0044] Figure 1 A device 1 for welding a workpiece W in a protective gas chamber 2 according to the prior art is schematically shown. The protective gas G can be introduced into the protective gas chamber 2 from a storage tank V via at least one line 3. For welding the workpiece W, there is a welding torch 4 for performing the welding process in the protective gas chamber 2. The fusible welding wire 5 is supplied from a storage barrel to the welding torch 4, and the storage barrel can also be arranged outside the protective gas chamber 2. The welding torch 4 generally has a gas channel 6 for supplying the protective gas G to the welding position S. The welding process takes place in the protective gas chamber 2 filled with the protective gas G, so that no oxygen can reach the welding position S and cause unwanted oxidation there. The atmosphere L of the protective gas chamber can be discharged or pumped out of the protective gas chamber 2 via at least one outlet 21. During the filling of the protective gas chamber 2 with the protective gas G, the existing air is also discharged or pumped out of the protective gas chamber 2 through this outlet 21.

[0045] Figure 2 Fig. shows a schematic view of an apparatus 1 for welding a workpiece W in a shielding gas chamber 2 using the method according to the invention, wherein the gas flow direction in the gas channel 6 can be reversed at least temporarily. At least during the welding process, the shielding gas chamber atmosphere L is at least temporarily suctioned from the welding position S through the gas channel 6 of the welding torch 4. The suctioned shielding gas chamber atmosphere L contains metallic dust (referred to as fumes), and thus does not contaminate the welding position S and the interior of the welding chamber 2. Since the welding process takes place in the shielding gas atmosphere within the welding chamber 2, there is no need for the shielding gas G to be additionally supplied to the welding position S through the welding torch 4, such that the gas channel 6 in the welding torch 4 can be used for suctioning the shielding gas chamber atmosphere L. Thus, commercially available welding torches 4 can be used for the welding process, and a complex design of the welding torch 4 with a separate suction channel is unnecessary. All that is required is that the gas flow direction in the gas channel 6 of the welding torch 4 is reversed at least temporarily at least during the welding process, such that the shielding gas chamber atmosphere L is specifically suctioned from the welding position S. A filter 7 for filtering metallic dust from the suctioned shielding gas chamber atmosphere can be arranged in the gas channel 6. Additionally, in order to oxidize the metallic dust in the suctioned shielding gas chamber atmosphere in a targeted manner and thus reduce the risk of ignition or explosion, a device 9 for mixing or swirling the suctioned shielding gas chamber atmosphere L with oxygen O 2 can be arranged in the gas channel 6. The device 9 is preferably arranged upstream of the filter 7.

[0046] Although other lines or pumps (not shown) can of course also be used for this purpose, before the welding process is carried out, the shielding gas chamber 2 can also be evacuated through the gas conduit 6 of the welding torch 4.

[0047] A sensor 14 for measuring the oxygen content c(O 2 ), a particulate sensor 20 for measuring the fume content or smoke concentration c(R), or a differential pressure sensor 15 for measuring the differential pressure Δp between the shielding gas chamber 2 and the environment U can be arranged in the shielding gas chamber 2. The sensor 14 for measuring the oxygen concentration c(O 2 ), the particulate sensor 20 for measuring the fume content c(R), and the differential pressure sensor 15 for measuring the differential pressure Δp between the shielding gas chamber 2 and the environment U are preferably connected to a control device (not shown) of the welding current source, such that the welding process can be controlled or adjusted according to the measured oxygen concentration c(O 2 ) and / or the measured fume content c(R) and / or the measured differential pressure Δp. For example, the welding process can be carried out only when the oxygen concentration c(O 2 ) in the shielding gas chamber 2 drops below a predetermined oxygen concentration threshold c(O 2 ) G (preferably 100 ppm) and / or the differential pressure Δp exceeds a predetermined differential pressure threshold ΔpG It preferably starts when the pressure is between 1 and 3 mbar.

[0048] During the filling of the protective gas chamber 2 with the protective gas G, the atmosphere L of the protective gas chamber can instead be discharged or pumped out of the protective gas chamber 2 through at least one outlet 21, or the existing air can be discharged from the protective gas chamber 2.

[0049] In addition, the storage chamber 16 can be connected to the protective gas chamber 2 by a pump 17, so that after the welding process, the atmosphere L of the protective gas chamber can be pumped from the protective gas chamber 2 into the storage chamber 16, and the protective gas G can be extracted and stored from there for subsequent welding processes. Through the storage chamber 16, any pressure fluctuations in the protective gas chamber 2 are also reduced by a pressure equalization line 19 with a stop valve 18, which occur, for example, during the movement of a robot (not shown) for manipulating the torch 4 or the workpiece W. By canceling or minimizing the pressure fluctuations in the protective gas chamber 2, smaller forces act on the robot, connectors, foils, seals, etc.

[0050] Figure 3 A preferred embodiment of a torch 4 suitable for implementing the welding method according to the invention is shown. Thus, the gas flow in the gas channel 6, which is usually used to supply the protective gas G to the welding position S, is at least temporarily reversed so that the atmosphere L of the protective gas chamber can be suctioned from the welding position S. The supplied welding wire 5 made of fusible material and the gas nozzle 12 of the torch 4 can also be seen.

[0051] Figure 4 Another preferred embodiment of a torch 4 suitable for implementing the welding method according to the invention is shown. If the opening 13 of the gas nozzle 12 is tapered accordingly, an optimization of the gas flow (e.g., laminar flow) of the suctioned atmosphere L of the protective gas chamber around the welding position S can be achieved. This makes it possible to ensure that the atmosphere L of the protective gas chamber and the dust contained therein are optimally suctioned in the area of the welding position S, and no contaminated protective gas G can escape to points inside the protective gas chamber 2 below the gas nozzle 12 of the torch 4.

[0052] Finally, Figure 5 A cooling device 11 for cooling the torch 4 or the suctioned atmosphere L of the protective gas chamber during the welding process through the gas channel 6 of the torch 4 is shown. Figure 5 A cooling device 11 with heat sinks is shown, which is cooled indirectly by cooling water KW, a cooling liquid, or a cooling gas. In addition, a baffle 22 is shown, which ensures laminar flow of the suctioned atmosphere L of the protective gas chamber in the area around the welding position S.

Claims

1. A method for welding a workpiece (W) in a shielding gas chamber (2), wherein before the welding process begins, the shielding gas chamber (2) is filled with shielding gas (G) via a corresponding line (3), and the workpiece (W) is welded using a welding torch (4) comprising a gas line (6) for supplying the shielding gas (G) and a fusible welding wire (5) which can be supplied to a welding position (S), characterized in that At least during the welding process, the flow direction of the shielding gas (G) in the gas channel (6) in the welding torch (4) is at least temporarily reversed so that a shielding gas chamber atmosphere (L) is sucked away from the welding position (S).

2. The welding method according to claim 1, characterized in that: Before the welding process begins, the shielding gas chamber (2) is evacuated by means of the welding torch (4) by suctioning the shielding gas chamber atmosphere (L) through the gas channel (6) before the shielding gas chamber (2) is filled with shielding gas (G).

3. The welding method according to claim 1 or 2, characterized in that: During the welding process, the protective gas chamber atmosphere (L) which is drawn through the gas channel (6) of the welding torch (4) is filtered.

4. The welding method according to any one of claims 1 to 3, characterized in that: During the welding process, the protective gas chamber atmosphere (L) which is drawn through the gas channel (6) of the welding torch (4) is cooled.

5. The welding method according to any one of claims 1 to 4, characterized in that: During the welding process, oxygen (O2) is supplied to the evacuated protective gas chamber atmosphere (L) through the gas channel (6) of the welding torch (4).

6. The welding method according to any one of claims 1 to 5, characterized in that: The oxygen concentration (c(O2)) and / or the flue gas content (c(R)) in the protective gas chamber (2) and / or the pressure difference (Δp) between the protective gas chamber (2) and the environment (U) are measured.

7. The welding method according to claim 6, characterized in that: The welding process is performed such that the oxygen concentration (c(O2)) in the protective gas chamber (2) drops to a predetermined oxygen concentration threshold value (c(O2) G ) is preferably less than 100 ppm, and / or the smoke content (c(R)) exceeds a predetermined smoke content threshold (c(R) G ) and / or the pressure difference (Δp) exceeds a predetermined pressure difference threshold (Δp G ) preferably starts at 3 mbar.

8. The welding method according to claim 6 or 7, characterized in that: The amount of the protective gas (G) supplied to the protective gas chamber (2) via the line (3) is regulated as a function of the measured oxygen concentration (c(O2)) and / or the measured flue gas content (c(R)) and / or the measured pressure difference (Δp).

9. The welding method according to any one of claims 1 to 8, characterized in that: After the welding process, the protective gas chamber atmosphere (G) is pumped out of the protective gas chamber (2) into a storage chamber (16).

10. A device (1) for welding a workpiece (W) in a shielding gas chamber (2), comprising a shielding gas chamber (2) with a line (3) for the inflow of shielding gas (G), and comprising a welding torch (4) for carrying out the welding process when a fusible welding wire (5) is supplied, wherein the welding torch (4) has a gas channel (6) for supplying the shielding gas (G), characterized in that The welding torch (4) is designed to draw a shielding gas chamber atmosphere (L) from a welding location (S) through the gas channel (6) at least during the welding process, wherein the gas flow direction in the gas channel (6) is at least temporarily reversed.

11. The welding device (1) according to claim 10, characterized in that The cross section (A) of the gas channel (6) for extracting the protective gas chamber atmosphere (L) from the welding position (S) is 3 mm 2 Up to 150mm 2 , and a gas nozzle (12) with a tapered opening (13) is preferably arranged in front of the opening of the gas channel (6).

12. The welding device (1) according to claim 10 or 11, characterized in that A baffle (22) is arranged on the welding torch (4).

13. The welding device (1) according to any one of claims 10 to 12, characterized in that An oxygen (O2) feed line (8) is arranged in the gas channel (6).

14. The welding device (1) according to any one of claims 10 to 13, characterized in that A cooling device (11) is arranged in the region of the gas channel (6).

15. The welding device (1) according to any one of claims 10 to 14, characterized in that The storage chamber (16) is connected to the protective gas chamber (2) via a pump (17) and via a pressure equalization line (19) with an integrated stop valve (18).

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