Method for tungsten inert gas welding

Abstract

A method and a welding torch for gas tungsten arc welding is provided for, wherein an electric arc burns between a non-consumable electrode and a workpiece. The interior of the electrode has a cavity through which an electrically conducting filler is fed in the direction of the workpiece, the filler being energized.

Claims

1. A method for tungsten inert gas welding, comprising: burning an arc between a non-consumable electrode and a work piece, wherein the electrode in its interior comprises a cavity, feeding an electrically conductive filler through the cavity of the electrode in a direction of the work piece, and the feeding of the filler is varied in such a manner that an oscillating movement having an oscillation frequency between 350 Hz and 450 Hz of the filler in the feed direction is superimposed on the feed, and wherein the filler is energized.

2. The method according to claim 1, wherein the filler is energized as a function of feed, temperature and/or material of the filler.

3. The method according to claim 1, wherein the electrode is energized with a welding current and the filler is energized with a heating current independently of the welding current.

4. The method according to claim 3, wherein the heating current is regulated or controlled as a function of a temperature of the filler.

5. The method according to claim 1, wherein the filler is electrically connected with current contact points of a heating current source and thereafter is introduced into the cavity of the electrode.

6. The method according to claim 5, wherein a distance of the current contact points to one another is changed.

7. The method according to claim 1, wherein a Joule's heat of the filler is adjusted.

8. The method according to claim 1, wherein the feed of the filler is adjusted dependent on a welding speed and/or a gap dimension of the work piece.

9. The method according to claim 1, wherein an oscillating frequency of this oscillating movement of the filler substantially corresponds to a frequency of a drop melting off the filler.

10. The method according to claim 1, wherein an additive gas is fed to the filler.

11. The method according to claim 1, wherein the filler is electrically insulated from the electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE shows a preferred configuration of a welding torch for tungsten inert gas welding according to the invention.

DETAILED DERIPTION OF THE INVENTION

(2) In the FIGURE, a preferred configuration of a welding torch for tungsten inert gas welding according to the invention is schematically shown and marked with 100. The welding torch 100 is equipped for carrying out a preferred embodiment of a method according to the invention. By means of the welding torch 100, a first work piece 151 is welded to a second work piece 152 by way of a joining operation.

(3) The welding torch 100 comprises an electrode 110, which tapers towards its side facing the work piece. The electrode 110 is formed as a hollow electrode and in its interior has a cylindrical cavity 200 which extends over the complete axial extent of the electrode 110.

(4) The first work piece 151 and the hollow electrode 110 are electrically connected to a welding current source 140. The hollow electrode 110 is thus energised with a welding current.

(5) The hollow electrode 110 in this specific example is formed from tungsten and is used as cathode. The first work piece 151 in this specific example is used as anode. It is mentioned that the hollow electrode 110 can also be used as cathode and the first work piece 151 as anode, for example when the hollow electrode 110 is formed from copper.

(6) An arc 120 burns between the hollow electrode 110 and the first work piece 151. Through the arc 120, the first and the second work piece 151 and 152 are at least partially melted, as a result of which a melt pool 160 is created.

(7) The welding torch 100 furthermore comprises a shielding gas nozzle 130 in order to feed a shielding gas in the form of a shielding as flow to the welding process or in the direction of the arc 120 or in the direction of the weld pool 160, indicated by reference number 131.

(8) Furthermore, an electrically conductive filler 210 is fed to the welding process, in particular through a feeding device 230. The filler 210 is designed wire-shaped and is fed through the cavity 200 in the direction 230a of the first and second work piece 151 and 152. The cavity 200 comprises an electrical insulation 201 in order to electrically insulate the filler 210 from the hollow electrode 110.

(9) Before the filler 210 is introduced into the hollow electrode 110, the filler 210 is electrically connected to two current contact points 221 of a heating current source 220. The current contact points 221 in this case are formed in particular as a slip contact. By means of the current contact points 221 and the heating current source 220, the filler 210 is energised with a heating current.

(10) By energising the filler 210 with the heating current, the filler 210 heats up. When the filler 210, in this case wire, has reached a predetermined temperature of for example 600 C., the feed commences. Here, the filler 210 is introduced into the cavity 200 so far that a tip 212 of the filler 210 projects out of the cavity 200 in the direction of the work piece 151.

(11) Through the arc 120, this tip 212 of the filler 210 is heated further. Through this heating, the filler 210 is melted at the tip 212. Consequently a molten drop 211 of the filler 210 is formed.

(12) Finally, the drop 211 detaches from the filler 210, passes into the melt pool 160 and forms a weld seam (joining connection between the work pieces 151 and 152). The forming of the drop 211 and the detaching of the drop 211 from the filler 210 and the transfer into the melt pool 160 is described as material transfer.

(13) The distance of the current contact points 221 relative to one another is variable during the welding process. The current contact points can also be arranged in front of the cavity in order to improve accessibility. Both current contact points 221 in this case can be shifted along the filler 210 independently of one another, indicated by the double arrow 221a. By adjusting the distance of the current contact points 221 and by adjusting the current strength of the heating current, a Joule's heat of the filler 210 is adjusted in particular.

(14) The Joule's heat in this case is the heat energy per time by which the filler 210 is heated because of its electrical resistance and because of their heating current.

(15) By means of the feeding device 230, the filler 210 can be fed or advanced or introduced further into the cavity 200. A feeding direction, in which a corresponding feed takes place, in this case corresponds to the direction 230a, which is directed towards the work pieces 151 and 152. The filler 210 can be present for example wound onto a reel and be unwound through the feeding device 230.

(16) The feed, that is the feed speed of the wire, can be practically varied through the feeding device 230. In particular, the feed is varied in such a manner that an oscillating movement of the filler 210 in feed direction is superimposed on the feed. The filler 210 in this case oscillates in and opposite to the feed direction 230a. A frequency of this oscillation corresponds to a natural frequency of the drop 211 and amounts to in particular 400 Hz. The detaching of the drop 211 is thus induced even more intensively.

(17) The welding torch 100, furthermore, comprises an additional gas feed 240 (only schematically indicated). By means of the additional gas feed 240, an additional gas in the form of an additional gas flow is fed to the filler 210, indicated by the reference number 241. The additional gas flow 241 in this case flows in feed direction 230a axially about the filler 210. Through the additional gas flow 241, gas flows onto the drop 211, as a result of which a surface tension of the drop 211 is reduced and the detaching of the drop 211 induced even further.

(18) For example, a gas mixture or argon and oxygen with an oxygen proportion of 10% is fed as additional gas in the form of the additional gas flow 241. Through the electrical insulation 201 between filler 210 and hollow electrode 110, the additional gas flow is likewise separated from the hollow electrode 110, so that a destruction of the hollow electrode 110 through the additional gas can be avoided.

REFERENCE LIST

(19) 100 Welding torch

(20) 110 Electrode, hollow electrode

(21) 120 Arc

(22) 130 Shielding gas nozzle

(23) 131 Shielding gas flow

(24) 140 Welding current source

(25) 151 First work piece

(26) 152 Second work piece

(27) 160 Melt pool

(28) 200 Cavity

(29) 201 Electrical insulation

(30) 210 Wire-shaped filler

(31) 211 Molten drop

(32) 212 Tip

(33) 220 Heating current source

(34) 221 Current contact point, slip contact

(35) 221a Double arrow

(36) 230 Feeding device

(37) 230a Direction, feeding direction

(38) 240 Additional gas feed

(39) 241 Additional gas flow