Method and apparatus for welding workpieces in a protective gas chamber - Patents.com

Abstract

The present invention relates to a method and apparatus (1) for welding a workpiece (W) in a protective gas chamber (2), comprising a protective gas chamber (2) having a line (3) for introducing a protective gas (G) and a welding torch (4) for carrying out a welding process while supplying a fusible welding wire (5), the welding torch (4) having a gas flow path (6) for supplying the protective gas (G).To prevent the accumulation of metal dust generated during the welding process and achieve the best possible weld quality, and to reduce the risk of fire or explosion due to unoxidized dust, the present invention proposes that the welding torch (4) is designed to draw the protective gas chamber atmosphere (L) from the weld point (S) through the gas flow path (6) by at least temporarily reversing the flow direction in the gas flow path (6) at least during the welding process.

Description

[Technical Field]

[0001] The present invention relates to a method for welding workpieces in a protective gas chamber, in which before the start of the welding process, a protective gas is filled into the protective gas chamber via a corresponding line, and the workpieces are welded using a welding torch that comprises a gas channel for supplying the protective gas and a meltable welding wire that can be fed to the welding point.

[0002] The present invention further relates to an apparatus for welding workpieces in a protective gas chamber, comprising a protective gas chamber having a line for introducing protective gas therein, and a welding torch for carrying out a welding process while supplying a meltable welding wire, the welding torch having a gas passage for supplying the protective gas therein. [Background technology]

[0003] The present invention is generally directed to the welding of workpieces in a protective gas chamber, particularly the build-up welding and additive manufacturing of metallic compacts, known, for example, under the terms Wire Arc Additive Manufacturing (WAAM) and Arc Directed Energy Deposition (Arc-DED). In the additive manufacturing of non-ferrous metal compacts, which have an affinity for oxygen, protecting the workpiece from oxygen is particularly important to prevent oxidation. Titanium and nickel, as well as their alloys, oxidize very strongly, so the welding process must be carried out under a protective gas atmosphere until the material cools below a critical temperature at which harmful oxidation occurs. For example, argon is often used as the protective gas for the protective gas chamber and also to protect the arc during the welding process. 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 large amount of protective gas is consumed. On the one hand, a low oxygen concentration in the protective gas chamber must be maintained despite the presence of existing leaks, and on the other hand, a large amount of clean protective gas must be continuously supplied to remove contamination from the protective gas chamber (fumes) due to the welding process. Furthermore, welding large workpieces, such as titanium aircraft parts, in protective gas chambers is particularly expensive, since large amounts of protective gas are required for inertization filling, and these protective gases cannot be used further after the welding process is completed.

[0004] Metal dust (so-called fumes) generated during welding in the protective gas chamber accumulate inside the protective gas chamber and on the surfaces of the workpieces, etc. During the welding process, fumes continuously accumulate inside the protective gas chamber, leading to contamination of the protective gas chamber and the structure of the workpieces or weld seams. Furthermore, this metal dust is particularly dangerous because it is not oxidized and can cause combustion or explosion. If the protective gas is sucked and filtered, preferably before being returned to the protective gas chamber, the non-oxidized dust accumulates on the filter, posing a significant fire or explosion hazard.

[0005] For example, DE 102015108131 A1 describes a method and an apparatus for producing, in particular, metal bodies by additive manufacturing methods, in which a metal starting material is melted by means of an electric arc in a protective gas chamber and deposited in layers.

[0006] U.S. Patent No. 6,380,515 discloses a welding torch that includes a gas passage for supplying protective gas to the welding point and a suction passage for suctioning exhaust gas from the welding point. However, the structure of the welding torch is relatively complicated. Summary of the Invention

[0007] The object of the present invention is to provide a method and an apparatus for welding workpieces in a protective gas chamber, which avoid or reduce metal dust (fumes) that accumulates in the protective gas chamber and deposits on the surface during the welding process, thereby ensuring the highest possible quality of the workpieces produced and eliminating the risk of fire or explosion due to dust that has not been oxidized inside the protective gas chamber. The consumption of protective gas should be minimized so that the associated costs can be reduced. The method and apparatus should be implemented or constructed as simply and cost-effectively as possible. The disadvantages of known methods and known apparatus are avoided or at least mitigated.

[0008] The object of the present invention is achieved by at least temporarily reversing the flow direction in the gas flow path for protective gas in the welding torch, at least during the welding process, and aspirating the protective-gas chamber atmosphere from the welding site. In the method of the present invention, the function of a conventional welding torch, in which protective gas is normally transported toward the workpiece through the hose package and gas flow path, is at least temporarily reversed, and the protective-gas chamber atmosphere is aspirated from the welding site through the gas flow path of the welding torch. Thus, at least during the welding process, the flow direction of the protective gas or protective-gas chamber atmosphere in the gas flow path of the welding torch is at least temporarily reversed, i.e., the protective-gas chamber atmosphere is actively aspirated from the welding site out of the protective-gas chamber and transported along the gas flow path and further along the hose package to the outside of the welding system. The aspirated protective-gas chamber atmosphere refers to the gas in the area of ​​the welding site, including the protective gas and the generated fumes. The fumes are aspirated directly at their point of generation via the welding torch, and substantially no contamination of the interior of the protective-gas chamber occurs. By selectively suctioning the protective gas chamber atmosphere at least temporarily from the welding site, only a small amount is suctioned, thereby reducing protective gas consumption and, consequently, production costs. At the outlet of the welding system, the suctioned protective gas chamber atmosphere mixes with ambient air, thereby oxidizing not-yet-oxidized metal particles and / or contained compounds in a controlled manner, preventing the generation of explosive dust. Because the welding process takes place in a welding chamber, which is always filled with protective gas via the protective gas supply, at least temporarily reversing the flow direction in the gas flow path of the welding torch can at least temporarily omit the supply of protective gas to the welding site via the gas flow path of the welding torch. This method is characterized by its simplicity, since conventional or slightly adapted welding torches can be used and only a device for at least temporarily reversing the gas flow direction in the gas flow path of the welding torch is required. Furthermore, the conservation of protective gas reduces costs and protects the environment.

[0009] The term "during the welding process" naturally also includes the phase before the welding process or before the ignition of the arc, the phase after the welding process, and the interruptions between the individual welding process phases. The statement that the flow direction is at least temporarily reversed during the welding process is intended to express the fact that the protective gas chamber atmosphere can be sucked away from the weld point or can be sucked continuously in periods before and after the welding process.

[0010] The additional statement that the flow direction is "at least temporarily" reversed is intended to express the fact that, during individual stages of the welding process, suction of the protective gas chamber atmosphere may not occur. Particularly during the arc stage, reversal of the flow direction and suction of the protective gas chamber atmosphere may be disadvantageous because turbulence may allow air to reach the arc.

[0011] If the protective gas chamber is filled with protective gas before the welding process begins, evacuating the protective gas chamber atmosphere through the gas flow path creates a negative pressure in the protective gas chamber when the protective gas chamber is evacuated through the welding torch. This reduces the amount of oxygen that must be transported out of the protective gas chamber along with the protective gas, making it easier to introduce the protective gas later. The evacuated protective gas chamber atmosphere is typically air, or a mixed gas if the protective gas chamber still contains residual protective gas.

[0012] The protective gas chamber atmosphere is drawn through the gas passage of the welding torch during the welding process, preferably at a volumetric flow rate of 5 to 100 l / min, more preferably 15 l / min. Such volumetric flow rates have proven to be suitable. To achieve such volumetric flow rates, the gas passage of the welding torch and the subsequent hose package must be, for example, 3 mm thick. 2 from 150mm 2 The actual cross section used will usually depend on the operating pressure of the welding chamber.

[0013] Before the welding process (where the protective gas chamber atmosphere is usually air), the protective gas chamber atmosphere is sucked out of the protective gas chamber via the gas flow path of the welding torch, preferably at a volumetric flow rate of 5 to 5000 l / min. In order to prepare the protective gas chamber as quickly as possible for the welding process, it is desirable to suck out the protective gas chamber atmosphere as quickly as possible. If such rapid operation via the welding torch is not possible, the protective gas chamber atmosphere can, of course, be sucked out of the protective gas chamber via another line.

[0014] According to a further feature of the present invention, the protective gas chamber atmosphere sucked through the gas passage of the welding torch during the welding process is filtered, so that metal dust can be selectively separated and treated. For filtering metal dust, filter solutions known for sucking welding fumes can be used.

[0015] It is also advantageous if the protective gas chamber atmosphere drawn through the gas flow path of the welding torch during the welding process is cooled. Because the arc generates very high temperatures at the welding point, cooling can protect the welding torch and subsequent components, such as the hose package and filter. Cooling can be achieved by both air and liquid, preferably within the welding torch or torch body, to ensure that the drawn-in protective gas chamber atmosphere is below a critical temperature that could destroy components of the welding system. For example, the mechanical strength of plastic hoses in the hose package can be lost due to the unacceptably high temperature of the drawn-in protective gas chamber atmosphere.

[0016] If oxygen is supplied to the protective gas chamber atmosphere drawn in during welding through the gas flow path of the welding torch, it can cause oxidation of flammable or explosive metal dust contained in the drawn-in protective gas chamber atmosphere. Controlling oxidation can reduce the risk of fire or explosion. Oxygen is typically supplied by supplying or mixing ambient air containing oxygen. If the drawn-in protective gas chamber atmosphere is filtered, oxygen is preferably supplied upstream of the filter to oxidize the metal particles before filtration.

[0017] In this case, it is advantageous if the protective gas chamber atmosphere drawn in during the welding process via the gas flow path of the welding torch is mixed or stirred with the supplied oxygen or ambient air in order to bring about optimal oxidation of the dust.

[0018] When the oxygen concentration in the protective gas chamber is measured, the welding process or the protective gas supply can be controlled or adjusted depending on the measured oxygen concentration in the protective gas chamber. The oxygen content or residual oxygen in the protective gas chamber can also be measured by appropriately positioned sensors.

[0019] The fume content or smoke concentration in the protective gas chamber can also be measured by a suitable sensor, for example a particle sensor, and the welding process can be controlled or adjusted depending on the measured smoke concentration in the protective gas chamber.

[0020] Furthermore, by measuring the pressure difference between the protective gas chamber and the environment, the overpressure or underpressure in the protective gas chamber can be reliably determined and the welding process can be controlled or adjusted accordingly. During arc operation, a low overpressure of at least a few mbar is aimed for in the protective gas chamber.

[0021] Advantageously, the welding process is initiated only when the oxygen concentration in the protective gas chamber is below 100 ppm and / or the differential pressure is above 3 mbar. Operating the protective gas chamber at a certain overpressure ensures that ambient air, and therefore oxygen, does not enter the protective gas chamber during the welding process, potentially leading to oxidation of the weld. To keep the load on the protective gas chamber and its seals as low as possible, the overpressure should not be too high and should be significantly below 3 mbar.

[0022] If the quantity or mass flow rate of the protective gas supplied via the line to the protective gas chamber is adjusted depending on the measured oxygen concentration and / or the measured fume content and / or the measured differential pressure, the consumption of the protective gas can be adapted to the actual conditions and the costs of the relatively expensive protective gas can be saved.

[0023] The protective gas is preferably supplied to the protective gas chamber via several lines and several inlets, which allows for very rapid filling of the protective gas chamber. A uniform gas flow towards the welding torch can also be achieved with several gas inlets. The inflow velocity can be very slow to prevent or reduce vortices and to avoid excessive stress on the seals of the protective gas chamber. The number and cross-section of the lines are adapted to the size of the protective gas chamber.

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

[0025] The supply of protective gas to the protective gas chamber before the welding process begins can be stopped as soon as an overpressure of preferably 1 mbar to 3 mbar is achieved in the protective gas chamber relative to the environment. The low overpressure ensures that sufficient protective gas is contained in the protective gas chamber. This prevents the waste of expensive protective gas.

[0026] If the protective gas chamber atmosphere is diverted from the protective gas chamber to a storage chamber after the welding process or the workpiece is completed, reusable protective gas can be stored for subsequent welding processes, thereby saving protective gas. Furthermore, pressure fluctuations in the protective gas chamber can be compensated for via the storage chamber. Such pressure fluctuations can occur, for example, during the operation of a robot manipulating a welding torch or workpiece. This occurs, for example, when the robot is rigidly connected to a flexible protective gas chamber shell and its movement is transmitted to the protective gas chamber shell. Compensating for or minimizing pressure fluctuations in the protective gas chamber further reduces the forces acting on the robot. After the contaminated protective gas chamber atmosphere around the weld is evacuated during the welding process, the protective gas remaining in the protective gas chamber is essentially clean and can be reused. Discharging the protective gas from the protective gas chamber creates a negative pressure that must be compensated for before the workpiece is removed from the protective gas chamber. The easiest way to do this is to fill it with ambient air. After the next workpiece is inserted into the protective gas chamber or before the next welding process is started, the protective gas chamber atmosphere is evacuated or sucked out of the protective gas chamber, and then protective gas is passed into the welding chamber.

[0027] The object according to the invention is also achieved by the above-mentioned device for welding workpieces in a protective gas chamber, in which the welding torch is designed to draw the protective gas chamber atmosphere from the welding point via a gas channel such that the flow direction in the gas channel is at least temporarily reversed at least during the welding process. See the above method description for the resulting advantages.

[0028] Advantageously, the cross section of the gas passage for drawing the protective gas chamber atmosphere from the welding point is 3 mm 2 and 150mm 2Such a gas channel cross section can be realized with a gas channel diameter between 2 mm and 14 mm, allowing for a sufficiently fast and efficient extraction of the protective gas chamber atmosphere and the metal dust contained therein from the weld. The selection of the appropriate gas channel cross section depends on the operating pressure or pressure difference of the protective gas chamber.

[0029] If a gas nozzle with a tapered opening is arranged in front of the opening of the gas channel, an optimized flow of the aspirated protective gas chamber atmosphere can be achieved, which allows optimal aspirating of the protective gas chamber atmosphere and the dust contained therein in the area of ​​the weld point and prevents any points below the gas nozzle of the welding torch where contaminated protective gas can enter the interior of the protective gas chamber.

[0030] According to a further feature of the invention, a filter is arranged in the gas flow path, which, as already mentioned, allows for optimal collection and disposal of metal dust.

[0031] When a baffle plate is placed on the welding torch, preferably on the gas nozzle of the welding torch, a laminar flow of the aspirated protective gas chamber atmosphere can be achieved in the area around the welding position. By properly designing the baffle plate, a flow field is created that is essentially oriented only in the direction of the arc.

[0032] Furthermore, an oxygen supply line can be arranged in the gas flow path to selectively oxidize the metal dust. If a filter is also arranged in the gas flow path, it is desirable that the oxygen supply, and therefore the oxidation of the dust, occurs upstream of the filter. In the simplest case, the oxygen supply line is realized by supplying ambient air.

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

[0034] In order to achieve as uniform a flow as possible in the gas channel, elements for guiding the flow of the aspirated protective gas chamber atmosphere can be arranged in the gas channel and on the gas nozzle. Such elements can be formed, for example, by lamellar parts.

[0035] A cooling device is preferably provided in the gas flow path area to protect the welding equipment components from unacceptably high temperatures and prevent damage. For example, it is advantageous to cool the aspirated protective gas chamber atmosphere to below 70°C to prevent damage to the welding equipment components. The cooling device can be air- and / or liquid-cooled and is preferably located as close as possible to the welding point to cool the aspirated protective gas chamber atmosphere as quickly as possible. For example, a water-cooling system, which is already included in the welding torch, can be used for this purpose, with corresponding cooling fins to dissipate heat loss.

[0036] Sensors for measuring oxygen concentration, particle sensors for measuring fume content or smoke concentration, and / or differential pressure sensors for measuring the differential pressure between the protective gas chamber and the environment may be provided in the gas chamber. The measured values ​​of oxygen concentration, fume content, and 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 a further feature of the invention, the storage chamber is connected to the protective gas chamber via a pump and a pressure equalization line with an integrated stop valve. After the welding process, the protective gas chamber atmosphere can be pumped out of the protective gas chamber by the pump with the stop valve 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. The protective gas chamber atmosphere can also be returned to an existing protective gas storage tank instead of its own storage chamber.

[0038] The invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram of an apparatus for welding workpieces in a protective gas chamber according to the prior art. [Figure 2] FIG. 2 is a schematic diagram of an apparatus for welding workpieces in a protective gas chamber using the method according to the invention, in which the flow direction in the gas flow passages is reversed. [Figure 3] FIG. 3 shows a preferred embodiment of a welding torch suitable for carrying out the welding method according to the present invention. [Figure 4] FIG. 4 shows a further preferred embodiment of a welding torch suitable for carrying out the welding method according to the present invention. [Figure 5] FIG. 5 shows a cooling device for cooling the welding torch or the protective gas chamber atmosphere that is drawn in during the welding process through the gas passages of the welding torch. DETAILED DESCRIPTION OF THE INVENTION

[0040] FIG. 1 schematically illustrates a prior art apparatus 1 for welding a workpiece W in a protective gas chamber 2. Protective gas G can be introduced into the protective gas chamber 2 from a storage tank V via at least one line 3. A welding torch 4 for performing the welding process is provided within the protective gas chamber 2. A meltable welding wire 5 is supplied to the welding torch 4 from a storage drum, which can also be located outside the protective gas chamber 2. The welding torch 4 typically has a gas flow path 6 for supplying protective gas G to the welding point S. The welding process is performed within the protective gas chamber 2, which is filled with protective gas G, so that oxygen does not reach the welding point S and cause unwanted oxidation there. The protective gas chamber atmosphere L can be evacuated or pumped out of the protective gas chamber 2 via at least one exhaust port 21. The existing air from the protective gas chamber 2 is also evacuated or forced out through this exhaust port 21 while the protective gas chamber 2 is being filled with protective gas G.

[0041] FIG. 2 schematically illustrates an apparatus 1 for welding a workpiece W in a protective gas chamber 2 using the method according to the present invention, in which the flow direction in the gas flow path 6 can be at least temporarily reversed. At least during the welding process, the protective gas chamber atmosphere L is at least temporarily drawn away from the welding site S via the gas flow path 6 of the welding torch 4. This drawn-in protective gas chamber atmosphere L contains metal dust, or fumes, and therefore does not contaminate the welding site S or the interior of the welding chamber 2. Due to the fact that the welding process is performed in the protective gas atmosphere in the welding chamber 2, there is no need to additionally supply protective gas G to the welding site S via the welding torch 4; instead, the gas flow path 6 of the welding torch 4 can be used to draw in the protective gas chamber atmosphere L. Therefore, 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 flow path is not necessary. All that is required is that the flow direction in the gas flow path 6 of the welding torch 4 be at least temporarily reversed, at least during the welding process, so that the protective gas chamber atmosphere L is specifically drawn away from the welding site S. A filter 7 for filtering metal dust from the aspirated protective gas chamber atmosphere can be arranged in the gas flow path 6. Furthermore, a device 9 for mixing or stirring the aspirated protective gas chamber atmosphere L with oxygen O2 can be arranged in the gas flow path 6 in order to selectively oxidize the metal dust in the aspirated protective gas chamber atmosphere and reduce the risk of fire or explosion. The device 9 is preferably arranged upstream of the filter 7.

[0042] The protective gas chamber 2 can also be evacuated via the gas passage 6 of the welding torch 4 before the welding process is carried out, although of course other lines or pumps (not shown) may be used for this purpose.

[0043] A sensor 14 for measuring the oxygen concentration c(O2), a particle 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 protective gas chamber 2 and the environment U may be arranged in the protective gas chamber 2. The sensor 14 for measuring the oxygen concentration c(O2), the particle sensor 20 for measuring the fume content c(R), and the differential pressure sensor 15 for measuring the differential pressure Δp between the protective gas chamber 2 and the environment U are preferably connected to a control device (not shown) of the welding power source, so that the welding process can be controlled or regulated depending on the measured oxygen concentration c(O2) and / or the measured fume content c(R) and / or the measured differential pressure Δp. For example, ... in the protective gas chamber 2, when the oxygen concentration c(O2) in the protective gas chamber 2 exceeds a predetermined oxygen concentration threshold c(O2). G , preferably below 100 ppm and / or only if the differential pressure Δp exceeds a predetermined differential pressure threshold ΔpG, preferably 1 to 3 mbar.

[0044] The protective gas chamber atmosphere L can be exhausted or pumped out of the protective gas chamber 2 via at least one exhaust port 21, or existing air can be exhausted from the protective gas chamber 2 during filling of the protective gas chamber 2 with protective gas G.

[0045] Furthermore, the storage chamber 16 can be connected to the protective gas chamber 2 via a pump 17, so that the protective gas chamber atmosphere L is pumped from the protective gas chamber 2 to the storage chamber 16 after the welding process, and the protective gas G is extracted therefrom and stored for the subsequent welding process. Via the storage chamber 16, pressure fluctuations in the protective gas chamber 2 are reduced via a pressure equalization line 19 having a stop valve. Pressure fluctuations occur, for example, during the operation of a robot (not shown) for manipulating the welding torch 4 or the workpiece W. By compensating or minimizing the pressure fluctuations in the protective gas chamber 2, the forces acting on the robot, connections, foils, seals, etc. are reduced.

[0046] 3 shows a preferred embodiment of a welding torch 4 suitable for carrying out the welding method according to the invention. The flow in the gas channel 6, which normally serves to supply protective gas G to the welding spot S, is thus at least temporarily reversed, so that the protective gas chamber atmosphere L can be sucked away from the welding spot S. Also visible are the supplied welding wire 5 made of a meltable material and the gas nozzle 12 of the welding torch 4.

[0047] 4 shows a further preferred embodiment of a welding torch 4 suitable for carrying out the welding method according to the invention. If the opening 13 of the gas nozzle 12 is correspondingly tapered, an optimized flow, e.g., a laminar flow, of the aspirated protective-gas chamber atmosphere L in the area surrounding the welding position S can be achieved. This ensures that the protective-gas chamber atmosphere L and the dust contained therein are optimally aspirated in the area of ​​the welding spot S, and that no points below the gas nozzle 12 of the welding torch 4 exist where contaminated protective gas G can enter the interior of the protective-gas chamber 2.

[0048] Finally, Fig. 5 shows a cooling device 11 for cooling the protective gas chamber atmosphere L drawn in during the welding process through the gas flow passage 6 of the welding torch 4 or welding torch S. Fig. 5 shows a cooling device 11 with cooling fins that is indirectly cooled via cooling water KW, cooling liquid, or cooling gas. Furthermore, a baffle plate 22 is shown, which ensures a laminar flow of the drawn-in protective gas chamber atmosphere L in the peripheral area of ​​the welding position S.

Claims

1. A method for welding workpieces (W) in a protective gas chamber (2), comprising: said protective gas chamber (2) being filled with protective gas (G) via a corresponding line (3) before the start of the welding process; The workpiece (W) is welded using a welding torch (4) having a gas passage (6) for supplying a protective gas (G) and a meltable welding wire (5) that can be supplied to a welding point (S), At least during the welding process, the flow direction in the gas flow path (6) for the protective gas (G) in the welding torch (4) is at least temporarily reversed and a protective gas chamber atmosphere (L) is sucked away from the welding point (S).

2. 2. The welding method according to claim 1, wherein before the start of the welding process and before the protective gas chamber (2) is filled with protective gas (G), the protective gas chamber (2) is evacuated through the welding torch (4) by sucking the protective gas chamber atmosphere (L) through the gas passage (6).

3. 3. The welding method according to claim 1, wherein the protective gas chamber atmosphere (L) drawn during the welding process through the gas flow passage (6) of the welding torch (4) is filtered.

4. 4. The welding method according to claim 1, wherein the protective gas chamber atmosphere (L) drawn during the welding process through the gas flow passage (6) of the welding torch (4) is cooled.

5. The protective gas chamber atmosphere (L) is introduced into the welding torch (4) through the gas flow passage (6) during the welding process. ２ 5. The welding method according to claim 1, wherein the welding current is supplied to the welding electrode.

6. The oxygen concentration (c(O ２ 6. The welding method according to claim 1, further comprising measuring the pressure difference (Δp) between the protective gas chamber (2) and the environment (U) and / or the fume content (c(R)).

7. The oxygen concentration (c(O ２ )) is a predetermined oxygen threshold (c(O ２ ) Ｇ ), preferably below 100 ppm, and / or the fume content (c(R)) is below a predetermined fume content threshold (c(R) Ｇ ) and / or the differential pressure (Δp) exceeds a predetermined differential pressure threshold (Δp Ｇ 7. The welding method according to claim 6, wherein the welding process is started as soon as the pressure exceeds 3 mbar.

8. The amount of protective gas (G) supplied to the protective gas chamber (2) via the line (3) is determined based on the measured oxygen concentration (c(O ２ 8. The welding method according to claim 6 or 7, wherein the heating time is controlled in dependence on the measured fume content (c(R)) and / or the measured differential pressure (Δp).

9. 9. The welding method according to any one of claims 1 to 8, wherein after the welding process, the protective gas chamber atmosphere (G) is delivered from the protective gas chamber (2) to a storage chamber (16).

10. An apparatus (1) for welding workpieces (W) in a protective gas chamber (2), comprising: a protective gas chamber (2) having a line (3) for introducing a protective gas (G); a welding torch (4) for carrying out a welding process while supplying a fusible welding wire (5); Equipped with The welding torch (4) has a gas flow path (6) for supplying a protective gas (G), The welding torch (4) is designed to draw a protective gas chamber atmosphere (L) from the welding point (S) through the gas flow path (6) by at least temporarily reversing the flow direction in the gas flow path (6) at least during the welding process.

11. The cross section (A) of the gas passage (6) for drawing the protective gas chamber atmosphere (L) from the welded part (S) is 3 mm ２ from 150 mm ２ 11. The welding device (1) according to claim 10, wherein a gas nozzle (12) having a tapered opening (13) is preferably arranged in front of the opening of the gas passage (6).

12. 12. The welding device (1) according to claim 10 or 11, wherein a baffle plate (22) is arranged on the welding torch (4).

13. Oxygen (O ２ 13. The welding device (1) according to any one of claims 10 to 12, wherein a supply line (8) for a gas (2) is arranged in the gas flow path (6).

14. 14. The welding device (1) according to any one of claims 10 to 13, wherein a cooling device (11) is provided in the region of the gas flow path (6).

15. 15. The welding device (1) according to any one of claims 10 to 14, wherein a reservoir chamber (16) is connected to the protective gas chamber (2) via a pump (17) and via a pressure equalization line (19) having an integral stop valve (18).

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