Submerged arc welding method

0001The invention relates to a submerged arc welding process with the preamble the specified claim 1 features and a Welder to perform this procedure.

0002The submerged arc welding process is a self-assembly process, wherein one or several wire electrodes under a layer a welding powder are melted.

0003In this method, a melt between the wire electrode and the workpiece trained arc part of the above Weld piled on welding flux, with some powder components evaporate. Together with the vapors of the metal melt form the vaporized powder constituents above the Weld gas filled a cavern. This is powder-sided by a layer of powder or melt slag and located about the Welding powder limited. The act vaporized powder constituents in the cavity as a protective gas, the molten end of the electrode, the released drops of the electrode material and the Weld protects against influences from the air atmosphere.

0004A disadvantage of the submerged arc welding, it is that the method only few powers offers to the welding results to improve or adapt the method to specific welding tasks. Measures used in this context in the Usually a variation of the welding parameters such. As the welding current, the welding voltage and the welding speed. Further changing the electrode polarity and the type of current and the Welding flux composition of the wire type and the wire diameter.

0005DD 37 867 describes a submerged arc welding process in which a Gas or gas mixture is introduced directly into the Schweißkaverne, by a gas nozzle is immersed in the Schweißkaverne. It takes place the gas supply obliquely to the orientation of the arc and below the arc approach point of the welding electrode. Through the gas supply to the burning of alloying elements can be reduced.

0006In one known from US 3,752,951 A method of welding Aluminium bronze is surrounding a one welding electrode Annular gap of the welding torch the weld supplied a welding powder. To an evolution of toxic gases through chemical reactions to reduce the melting of the welding powder or prevent, of the weld through the annular gap is also fed to a gas.

0007restrict further developments of the submerged arc welding process mainly on the use of new welding flux and new solid and flux-cored wire.

0008Against this background, the present invention, the object invention to develop a submerged arc welding method in which the Welding process is improved so that the energy input into the Workpiece is improved and changed the weld geometry positive becomes.

0009This object is inventively achieved by a submerged arc welding process having the features indicated in claim 1 dissolved. Advantageous developments of the invention will be made the dependent claims, the following description and the drawings.

0010In the submerged arc welding method of the invention is a Welding electrode sealed under a layer of powder in an arc. The welding electrode is in the welding direction behind a welding powder feed out. An above the arc approach point the welding electrode supplied gas, the arc constricted.

0011The constriction of the arc through the gas supply leads to a reduction the arc diameter and thus to a reduction the arc cross section. This increases the power density increases the arc extent that forms a plasma arc. This results in several advantages, including a lower influence of Welding parameters on the arc shape, a lesser influence of Changes in distance between the torch and workpiece on the penetration shape, a deep penetration and high welding speed belong. Furthermore, a low heat transfer to prove of the base material, the very smooth weld surface and a good Endgasung of highly heated molten bath to be advantageous.

0012The Lichtbogeneinschnürung is preferably introduced from the outside, in the additional gas in the forming under the welding powder Cavern is introduced. In contrast to the original caused by vaporized powder components and metal vapors Gas filling the cavern, the externally added gas a significantly lower in temperature. This cools the arc edge zone and from there is a thermal contraction of the arc.

0013Suitably, the additional gas above the arc approach point the welding electrode is introduced into the cavern. In this way it is ensured that the entire arc edge zone is cooled by the additional gas.

0014In a preferred process embodiment, the additional gas introduced via a welding torch into the cavern. In this case can direct the gas flow so special burner nozzle, that the gas very close to the electrode tips and there accreting arc is introduced and the gas flow the arc concentric wrapped.

0015the gas volume flow is advantageously in a range of 10 to 45 l / min, wherein the outflow velocity of the gas 7-30 m / s. At these flow rates and / or discharge velocities penetrates the gas the Schweißpulveraufschüttung and then the liquid slag layer without welding powder all blow, and disturb the welding process. After flowing around the gas stream the wire electrode and the arc, wherein the gas stream sufficient to dissipate as much heat from the arc edge zone, that the arc is thermally constricted. Another positive Effect of a gas stream with the dimensions described above is evident in its appearance to the melt of the base material. Due to its kinetic energy of the inert gas flow exerts Pressure to the molten bath, so that this mechanical influence the melt promotes penetration addition.

0016The mechanical control of the melt can be especially effective be made when the additional gas via at least one external Feed is introduced into the cavern. Here, the gas supply decoupled from the welding torch and is via one or several gas pipes. Similar to the supply of gas through the welding torch, penetrate the or the gas flows the bulk powder and the slag layer. By a specific geometric orientation the gas pipes may constricted arc as described above be mechanically enhanced the penetration of the weld will.

0017It is advantageous if the gas volume flow in the external gas supply is in a range of 5 to 40 l / min, at discharge velocities from 10 to 95 m / s. Depending on the welding task, however, other Settings of the volume flow and the extrusion speed the gas supply possible.

0018active gases are preferably used as additional gases provided. To show Welding with carbon dioxide very good results. Responsible this is the high thermal conductivity of the CO₂That the energy input additionally improved in the workpiece. Ultimately, the choice is gas but welding task, in particular of the type to be welded to the Materials, dependent, so that inert gases and gas mixtures, may be composed of inert and active gases used.

0019An apparatus for the submerged arc welding method of the invention has a submerged arc welding torch and a Powder feed, whereby the welding torch in the welding direction behind the welding flux supply is arranged. In addition, are expediently Means are provided with which additional gases in the weld can be introduced. These agents are the targeted modulation the arc and the workpiece melt provided.

0020Advantageously, the welding torches this one to the welding electrode concentric gas nozzle. In contrast to the welding torches, the are used in the conventional submerged arc welding and in Essentially of an electrode holder with a current contact nozzle consist through which a consumable electrode is fed, is at the welding torch for the submerged arc welding method of the invention an additional nozzle to the electrode and the electrode holder enveloping arranged. In this way, similar to this Welding torch the employed in gas metal arc welding Burner, the gas feed mainly for focusing the arc is provided, while in gas metal arc welding to protect the weld from the atmosphere and for ionizing the arc gap is.

0021The outlet opening of the gas nozzle is suitably designed annular. Here, the opening of the nozzle ring is the inner wall and the opening concentrically erupting welding electrode educated. This arrangement ensures that the electrode and thus the faceted this arc over the entire circumference are coated evenly from the gas stream. In a preferred Embodiment of the welding torch, the lower edge of the gas nozzle a distance of 8 to 12 mm for the lower edge of the current contact nozzle on. The distance between the lower edge of the gas nozzle and the workpiece surface is preferably in a range of 15 to 25 mm. If using a submerged arc welding wire having a diameter of 4 mm has a gas nozzle inside diameter of 6 to 10 mm as proved particularly advantageous. This information is purely exemplary. Thus, the size and spacing information can accordingly in the application be optimally adjusted.

0022Preferably, the burner head on a water cooler. This is in Generally required, since the head of the welding torch and thereby an outer wall of the burner head forming cap be performed as close to the welding point that they warmed up with the Schweißpulveraufschüttung come into contact or in this immerse. In addition to protection of the burner head prevents Water cooling also that the supplied gas nozzle exit before the is preheated and kontraktierenden as part of its arc Effect loses.

0023It may also be advantageous to provide an external gas supply. In this case, the gas supply independent of the welding torch, d. h., the device may comprise a conventional submerged arc welding torch exhibit. In addition, one or more gas tubes arranged that the gas to the arc and the workpiece melt out. In a preferred embodiment, the inner diameter is the gas pipes 3 mm. Depending on the welding conditions and the number of gas tubes used, the inner diameter also have a different size. Furthermore, it is also conceivable that the supply of additional gas at the same time both from an external supply via one or more gas tubes as well as on the above-described modified submerged-arc welding torch takes place with an additional gas nozzle.

0024The invention is described below based on illustrated in a drawing Embodiments explained. Show it:<dl tsize="6"><dt>Fig. 1</dt><dd>a schematic of the submerged arc welding method of the invention and the space provided Welding apparatus, in which an additional gas via a arranged on the welding torch gas nozzle is supplied in section along the weld seam,</dd><dt>FIG. 2</dt><dd>a longitudinal section of the burner head with a gas nozzle, the used in the welding process of the invention is and </dd><dt>Fig. 3</dt><dd>a schematic of the submerged arc welding method of the invention and the space provided Welding apparatus, in which the additional gas via a external gas supply is fed in representation as in FIG. 1,.</dd></dl>

0025Fig. 1 shows a workpiece 2 on which a welding powder feed 4 is a Layer welding powder 6 has piled up. When welding powder feed 4 is a powder feed as the submerged arc welding is known per se and is in the drawing only by the presented end region of the feeding tube.

0026In welding direction A behind the welding powder supply 4 is a submerged arc welding torch 8 arranged. Between its consumable Electrode 10 and the workpiece 2, an arc burns 12 and forms one of vaporized powder constituents and the metal vapors Melt formed gas filled Schweißkaverne 14. Schweißkaverne 14 is powder-side by a layer of liquid slag 16, which has formed from molten powder constituents, limited. These Slag layer 16 is piled together with the above Welding powder 6 penetrated by the electrode 10th

0027In Fig. 2 a burner head of the submerged arc welding torch 8 is in detail shown. This includes an electrode holder 18 for guiding of the electrode 10. The electrode holder 18 is formed shaped heel and tapers welded side to a paragraph 20. In the longitudinal direction the electrode holder 18 through a channel 22 centrally breached.

0028At the paragraph 20 of the electrode holder 18 closes welding other a current contact nozzle at 24th This has welded side a paragraph 28, via which it tapers radially. This taper is in the range the welding end of the current contact nozzle 24 through a conical Tapering continued. The current contact nozzle 24 has longitudinally an opening 26.

0029Through the channel 22 of the electrode holder 18 and the perforation 26 of the current contact nozzle 24, the electrode 10 of the welding point supplied. The dimensions of the opening 26 are designed so that the electrode 10 for applying the welding voltage conducting against the inner wall of the opening 26th

0030The electrode holder 18 is in the direction of the weld a hollow, open on both sides rotating body 30 extended. there is the contact area between the electrode holder 18 and the Rotating body 30 is sealed by an axial sealing 32nd welding side the opening of the rotary body 30 is closed by a gas nozzle 34th The gas nozzle 34 has a central opening 36, by the concentrated sweat-side opening of the rotating body 30 becomes. The rotary body 30 and the gas nozzle 34 form the closure cap 38th

0031In the cavity of the rotating body 30, a part of paragraph 20 the electrode holder 18 and the current contact nozzle 24 in which the inner wall of the rotating body 30 is profiled such that a Opening is created whose shape is complementary to the outer shape of the shoulder 20, the electrode holder 18 and to the outer shape of the current contact nozzle 24. This is from the shoulder 20 and the current contact nozzle 24 partly justified and partly broken through with little play. In the area the conical tip of the current contact nozzle 24 widens the opening and forms the welding side closed by the gas nozzle 34 Space 40. The space 40 and the opening 36 of the Gas nozzle 34, the consumable welding electrode 10 of the welding point supplied.

0032Inside its outer wall of the rotary body has 30 channels 42 for water cooling. This is shown in FIG. 2 by three cooling channels shown 42 that the rotary body 30 near its outer wall circumferentially rotate.

0033Furthermore, to the rotary body 30 feed channels 44 for introducing a gas stream B provided. These extend from the outer wall the rotating body 30 near the seal 32 initially radially inward and obliquely inward and to the fusion site by the rotary body 30 into the space 40. The through feed channels 44 introduced gas exits the chamber 40 through an annular gap, which by of the opening 36 of the gas nozzle 34 and the electrode 10 is formed is, along the electrode 10th

0034As FIG. 1 reveals, the gas passes through the welding powder 6 and the subsequent slag layer 16 and enters the Schweißkaverne 14 where there is the arc 12 is constricted and the material melt mechanical influences.

0035In Fig. 3 is a submerged arc welding method and required for this purpose Welding device shown with an external gas supply. On the work piece 2 is located above the welding point through the welding powder feed 4 welding powder 6 piled. The Schweißpulveranschüttung is through the electrode 10 of a conventional submerged-arc welding torch 46 punctured. Between the melting End of the electrode 10 and the workpiece 2, the arc 12 is formed. This burning in the Schweißkaverne 14, the torch end is limited by the slag layer 16th In welding direction A behind the submerged arc welding torch 46 is 48 arranged a gas pipe. This is immersed in the deposit of the welding powder. 4 The gas pipe 48 C is provided for the supply of a gas stream containing the Welding powder 6 and the subsequent slag layer 16 penetrates and then the arc 12 is constricted and the melt of the workpiece 2 mechanically influenced. To this end, the gas tube 48 connected to a gas supply, not shown in the Fig. 3 is.

LIST OF REFERENCE NUMBERS

0036<dl tsize="2" compact="compact"><dt>2</dt><dd>workpiece</dd><dt>4</dt><dd>Welding powder feed</dd><dt>6</dt><dd>welding powder</dd><dt>8th</dt><dd>Submerged arc welding torch</dd><dt>10</dt><dd>electrode</dd><dt>12</dt><dd>arc</dd><dt>14</dt><dd>Schweißkaverne</dd><dt>16</dt><dd>slag layer</dd><dt>18</dt><dd>electrode holder</dd><dt>20</dt><dd>paragraph</dd><dt>22</dt><dd>channel</dd><dt>24</dt><dd>current contact nozzle</dd><dt>26</dt><dd>perforation</dd><dt>28</dt><dd>paragraph</dd><dt>30</dt><dd>rotating body</dd><dt>32</dt><dd>seal</dd><dt>34</dt><dd>gas nozzle</dd><dt>36</dt><dd>perforation</dd><dt>38</dt><dd>cap</dd><dt>40</dt><dd>room</dd><dt>42</dt><dd>Channels for water cooling</dd><dt>44</dt><dd>supply channels</dd><dt>46</dt><dd>Submerged arc welding torch</dd><dt>48</dt><dd>gas pipe</dd></dl><dl tsize="1" compact="compact"><dt>A</dt><dd>welding direction</dd><dt>B</dt><dd>gas flow</dd><dt>C</dt><dd>gas flow</dd></dl>