WO2017114722A1 - Method and device for welding seam joints using a multi-electrode assembly - Google Patents

Abstract

The invention relates to a method for welding seam joints on metal components using a multi-electrode assembly (1) with at least two welding electrodes (4) which are arranged one behind the other in a welding direction. The welding electrodes (4) of the multi-electrode assembly (1) generate a common melt bath simultaneously. The method has a step of controlling the welding current of each welding electrode (4), wherein the first welding electrode (4) leading in the welding direction is operated with a direct current, and at least one second welding electrode (4) trailing in the welding direction is operated with an alternating current. The voltage of the second welding electrode (4) is held at a voltage which is maximally 50%, preferably maximally 20%, of the maximum value of the voltage of the first or second welding electrode (4) at least once during each period for a specified holding time.

Description

 METHOD AND DEVICE FOR WELDING SUTURE JOINTS USING A MULTI-EDGE ARRANGEMENT

The invention relates to a method for welding seam joints to metal components using a multi-electrode arrangement having at least two welding electrodes arranged one behind the other in a welding direction, the welding electrodes of the multi-electrode arrangement simultaneously producing a common melt bath, the method comprising controlling the welding current of each welding electrode ,

In particular, the invention relates to a method for submerged-arc welding of seam joints on metal workpieces

Use of an arrangement of welding heads for providing in each case a wire or band electrode as Mehrelektrodenan ^¬ order for generating multiple welding arcs in a single melt bath in a single seam, said welding heads with a welding power source in electrical

Active compound stand.

The invention also relates to an apparatus for the welding of seam joints in metallic components comprising a multi-electrode arrangement (1) having at least two welding electrodes which are arranged in a welding direction one behind the other, wherein the welding electrodes of the multi-electrode array simultaneously generate a common molten bath, at least one welding ^¬ current generator with means for controlling the welding current of each welding electrode.

Submerged arc welding is an arc welding process in which the welding arc burns between the wire electrode material and the workpiece to be welded. The special The process is characterized in that the welding arc is covered by a granular powder. As weld filler wire or strip usually serve electrodes and a Schweißpul ^¬ ver. The wire or tape electrodes are formed by a forward feed system conveyed to the welding point. The welding flux passes from a reservoir through a tube by gravity or through a pneumatic conveying system also to the weld site and thereby covers the molten bath generated by the Schweißlichtbo ^¬ gen against harmful influences of the atmos- phere from.

The submerged arc welding process is usually carried out as ^so-¬-called Eindrahtschweißverfahren as well as a parallel wire welding and tandem welding process. In parallel wire welding, two or three smaller diameter wire electrodes are melted instead of a common arc wire. The advantage of this process variant is an increase in the Abschmelzleis ^¬ tion, which goes hand in hand with a higher welding speed. Basically, the increase in welding speed limits. In order to weld through the same cross sections, the welding current strengths must be increased. The higher the number of welding heads used and thus the generated arcs in a single melt bath, the stronger influence the magnetic fields of the individual welding electrodes of the multi-electrode arrangement. The so-called penetration depth is given only for the leading in the welding direction of the first arc, the operation of the trailing arcs is greatly attenuated. The result is that as the number of arcs running one behind the other and the overall increase in the total current increases, the welding speed can be increased, but the burn-in loss that occurs as a result of the speed increase is less and less balanced. The welding speed can therefore not be linear with the number of used Increase welding heads. In particular, the influence

Arcs of the individual welding heads so that from a certain number of welding heads used no stable melt bath can be achieved.

A submerged-arc multi-wire welding system is known, for example, from EP 0 116 664 A1.

The document assumes that two-wire submerged arc welding doubles the possible welding speed, triples three wires, and quadruples four wires, although the use of more than four prior art wires is not common.

In practice, however, has proven that a quadrupling of welding speed using four wires is not actually achieved and that the United ^¬ application of four wires is hardly controllable because of a relatively uncontrolled Herten molten bath in practice.

The invention is therefore based on the object to provide a method of the type mentioned, which is also improved in terms of the welding speed to be achieved, the method is basically not on the

 Use of the number of wire electrodes or the welding heads is limited to a multi-electrode arrangement.

The object underlying the invention is achieved by a method having the features of independent claims 1 and 12. Advantageous embodiments of the invention will become apparent from the dependent claims.

According to one aspect of the invention, a method of welding seam joints to metal components using proposed a multi-electrode arrangement with at least two welding electrodes, which are arranged one behind the other in a welding direction, wherein the welding electrodes of the

Multi-electrode arrangement simultaneously produce a common melt bath, the method comprising a control of the welding current of each welding electrode, wherein the first in

Welding direction leading welding electrode with DC or AC or three-phase alternating current is operated and at least a second trailing in the welding direction welding electrode is operated with AC, wherein the AC ^¬ voltage of the second welding electrode is held at least once during each period over a predetermined holding time on a span ^¬ tion , which is at most 50%, preferably at most 20% of the maximum amount of voltage of the first or second welding electrode.

A period in the sense of the invention is a successive positive and negative half-cycle. The period duration is equal to the reciprocal of the frequency of the alternating current.

According to the invention, at least once during each period, the voltage of the welding electrode is maintained at a relatively low level over a predetermined holding time, for example of the order of microseconds, milliseconds, or seconds, which is at most 50%, preferably at most 20% maximum amount of voltage of the first or second welding electrode. The voltage can the example, held on the hold time to zero ^¬. The term "magnitude" in this sense is to be understood mathematically During the period, the voltage has a positive maximum and a negative maximum Between the positive and the negative maximum, a holding time is provided in which the melting rate of the second welding electrode is at most 50%. preferably at most 20% of the possible full Abschmelzleistung. The voltage applied to the AC powered AC welding electrode does not necessarily have a sinusförmi ^¬ ges signal, but the signal may also

be formed rectangular, triangular or sawtooth.

In a preferred variant of the invention it is provided that the voltage of the second welding electrode after each

Half-period over a predetermined holding time is maintained at a voltage which is at most 50%, preferably at most

 20% of the maximum amount of voltage of the first or second welding electrode.

In a preferred variant of the process according to the dung OF INVENTION ^¬ the second welding electrode with a pulsed is

AC voltage operated.

For example, the AC voltage of the second welding electrode can be modulated by means of a function generator.

In a particularly preferred and advantageous variant of the process according to the invention it is provided that a target ^¬ voltage function for the alternating-current characteristic of the two-th welding electrode is predetermined and by means of a

Function generator of a control electronics of a welding ^¬ current generator is traced.

It is both possible to operate the second welding electrode with a single-phase alternating voltage as well as with a three-phase alternating voltage.

In an expedient embodiment of the method according to the invention, it is provided that the multi-electrode arrangement comprises at least three welding electrodes, wherein a third or further welding electrode trailing in the welding direction is held at a voltage at least once during each period over a predetermined holding time which is at most 50%, preferably at most 20%, of the maximum voltage of the respective welding electrode.

According to the invention it is provided that the second, third or each further trailing in the direction of welding Schweißelekt ^¬ rode operated in each case periodically with greatly reduced power ben is, so that this welding electrode is substantially melted only passively during the hold period, namely by the heat of already generated by the leading welding electrode melt bath. , When the holding time of the third or further welding electrode coincides with a multi-electrode drive North ^¬ voltage or at a Mehrelektrodenschweißung with three or more electrodes with the maximum magnitude of the voltage of each of the leading in the direction of welding, preferably an immediate bar adjacent welding electrode is particularly favorable. In this case, the trailing welding electrode is always operated with reduced or no appreciable welding power, when the respective leading welding electrode is operated at maximum power.

The terms "leading" and "lagging" in the sense of the present invention refer to the spatial arrangement of the welding electrodes to each other, since the welding electrodes of a welding electrode assembly in the context of the present invention are moved parallel in time relative to the workpiece. Those skilled in the art will recognize that it is not important in this context whether the welding electrodes are moved with respect to the stationary workpiece or the workpiece with respect to the fixed welding electrodes. In an advantageous variant of the method according to the

Invention in which the seam of the workpiece is added in multiple layers, wherein a first layer is produced in a first welding ^¬ process in a first welding direction and a second layer with the same multi-electrode arrangement in a second welding direction, wherein the first and the second welding ^¬ direction different From one another it can be provided that in each case a switching of the current supply of the first and the trailing welding electrode from AC to DC or vice versa takes place. In an arrangement of two welding electrodes as so-called tandem ^¬ may be provided both welding electrodes from AC to DC or vice versa switch. In an arrangement of three welding electrodes, the average welding electrode must not be switched, in an arrangement of four or more welding electrodes can each be switched, only the first and the last leading to ^¬ hurrying welding electrode. Such

Switching is only useful when the first leading in welding direction ^¬ welding electrode is operated with direct current.

In the context of the invention, it may also be provided to operate the first electrode leading in the welding direction with alternating current as a phase alternating current or as a three-phase alternating current.

Characterized in that the invention provides that in each case a welding position in a first direction and a second Schweißla ^¬ ge is added in a second direction, on the one hand, the welding speed is increased, since a conversion of the electric ^¬ denanordnung of and / or the workpieces is not required On the other hand, the method according to the invention has the advantage that three-axis tension conditions or dreidimensiona ^¬ le voltage curves be avoided. This is automatic less rework, such as calibration, re-rolling or straightening the workpieces required.

Preferably, the method is performed as a method of sub-powder welding using an array of welding heads to provide the welding electrodes, wherein the welding electrodes are formed as wire or tape electrodes. The invention is not limited to submerged arc welding, but other welding methods using the principle of the invention are practicable and in the context of

Invention. Another aspect of the invention relates to an apparatus for welding seam joints to metal components comprising a multi-electrode assembly having at least two

Welding electrodes arranged in succession in a welding direction, wherein the welding electrodes (4) of the multi-electrode assembly (simultaneously creating a common melt bath, at least one welding current generator with means for controlling the welding current of each welding electrode, wherein the first welding direction leading welding electrode with DC or AC or three-phase alternating current is supplied with current and at least one second welding direction trailing welding electrode is energized with alternating current and the welding current generator is designed so that the voltage of the second welding electrode at least once during each period over a predetermined holding time can be maintained at a voltage not exceeding 50%, preferably at most 20% of the maximum amount of voltage of the first or second welding electrode. The invention will be explained below with reference to the accompanying drawing figures.

FIG. 1 shows a multi-electrode arrangement for use with the method according to the invention,

Figure 2 shows the circuit diagram of the secondary part of a welding ^¬ power generator for use in the method according to the invention,

FIG. 3 shows an alternative embodiment of the secondary part of the welding current generator shown in FIG. 2,

FIG. 4 shows a voltage function for the alternating current characteristic of a welding electrode operated according to the method according to the invention,

Figure 5 shows an alternative voltage function for the AC characteristic of the welding electrode and

FIG. 6 shows a further alternative voltage function for the AC characteristic of a welding electrode operated with three-phase AC voltage according to the method according to the invention.

Figure 1 shows a multi-electrode assembly 1 according to the invention, which is part of a device for submerged arc welding. Means for applying welding powder and suction of residual powder and means for guiding the multi-electrode assembly 1 relative to one or more workpieces are not shown in the drawing for reasons of simplicity.

The method according to the invention provides for welding seam joints on metal components using the multi-electrode arrangement 1 shown in FIG Seam joint is added in multiple layers between the components, wherein a first layer is generated for example in a first welding operation in a first welding direction and at least one second layer with a second welding operation in a second welding direction.

The multi- ^electrode arrangement 1 used for this purpose, shown in FIG. 1, comprises three guide tubes 2 with a nozzle 3 and respective wire electrodes 4 emerging from the nozzle 3. The wire electrodes 4 are respectively fed to the relevant nozzle 3 via a feed system (not shown).

A guide tube 2 and a nozzle 3 form a welding head 5a, 5b, 5c in the sense of the present invention.

By means of the multi-electrode arrangement 1, a welding track 6 is produced in a seam joint of a metal component or second metal components, which extends between the points A and B.

The multi-electrode arrangement 1 according to the invention comprises a total of three welding heads, of which a first welding head 5a and a third welding head 5c are arranged symmetrically with respect to a welding head 5b. All wire electrodes 4 of the

Multi-electrode arrangement 1 simultaneously generate an arc during the welding process, with all the wire electrodes 4 simultaneously producing a common melt bath.

The wire electrodes 4 as welding electrodes according to the invention are connected to a welding power source, for example to a welding power generator.

The welding power generator is designed, for example, as a transformer with a primary side 7 and one or more secondary parts 8. The welding power generator further comprises at least one higher-level controller 9 and at least one microprocessor 10, which determines the current characteristic of the current emitted by the secondary part 8. The secondary part 8 is designed so that it can generate both direct current and alternating current of a given characteristic. The secondary part 8 is on the one hand to the workpiece and on the other hand to a

Wire electrode 4 connected as a welding electrode. In the described embodiment, each Drahtelek ^¬ electrode 4 is connected to a secondary part 8. In the event that the secondary part 8 is to generate a wire phase alternating current, preferably each wire electrode 4 is at least two

Abutments 8 connected.

By means of the microprocessor 10 allows you to control the secondary part 8 of the welding power generator so that, for example, a pulsed AC with a predetermined voltage function (target voltage function) can be generated at the respective wire electrode 4.

The microprocessor 10 includes a function generator 11 which digitally generates a predetermined voltage function. The microprocessor 10 controls two ideal switches 12 in the secondary part 8, by means of which, for example, an alternating voltage with the desired voltage characteristic can be generated on the terminals 13 and 14 for the workpiece on the one hand and the wire electrode 4 on the other hand. The alternating voltage is generated, for example as pulsed alternating ^¬ voltage by pulse width modulation, wherein the control of the secondary part 8 is made in the variant shown in Figure 2 as so-called Class-D circuit. The circuit of the secondary part 8 according to the circuit diagram shown in FIG. 3 is designed as a so-called 2Q circuit, in which the ideal switches 12, which may be designed, for example, as transistors, are driven in parallel.

Incidentally, the same components are represented by the same reference numerals in Figures 2 and 3.

In Figures 4 to 6 show different AC voltage saddle ^¬ rakteristiken for the operation of the wire electrode 4 are shown, with the circuits according to Figures 2 and 3

can be generated in principle and are given in the context of the method of the invention, for example, a trailing in the welding direction wire electrode 4.

FIG. 4 shows a pulsed alternating current, the voltage of which, after every half-cycle in the order of magnitude of milliseconds, is kept at a voltage which in the exemplary embodiment shown is zero. The voltage can not exceed 20% of the maximum amount of voltage. This is to be understood as the absolute amount of the voltage regardless of the polarity.

The time period T is, for example, a cycle over 360 ° of a sine wave, in which case the half period is 180 °. The hold time is indicated by t _h in the diagram shown, in which the voltage is plotted over time.

4 shows a pulse current with a square-wave signal with the period / period T. Figure 5 illustrates an alternating current with an approximately sinusoidal signal, a holding time _h t in milliseconds after each half-oscillation or is provided after each half period. FIG. 6 shows the voltage function of a three-phase alternating voltage with three approximately sinusoidal signal waveforms, each signal being kept in the range of zero voltage after every half-cycle in the range of milliseconds. The magnitude of the voltage during the holding time t may not necessarily be zero _h, it must, for example, 50% or 20% or belie ^¬ bige intermediate values between 50% and 0% of the amount of the maxima ^¬ len voltage amount. In the illustrated in Figure 6 functions voltage, the holding times t _h all three phases so temporally adjacent to each other provided that the power of the respective wire electrode between two phases, that is reduced to 240 ° or is zero.

Figures 4 to 6 show, respectively, the voltage function for a wire electrode 4, wherein the 4 to 5, the voltage function ^¬ shows the voltage function for a three-phase alternating current for a single phase and FIG. 6

In the method according to the invention it is provided that, for example, the multi-electrode arrangement 1 is guided from point A to point B with respect to the workpiece, the third welding head designated by 5c comprising the first wire electrode 4 leading in the welding direction, which is operated with direct current. The second trailing electrode wire 4, which is supplied via the second welding head 5b is operated with exchangeable ^¬ current, in which a characteristic of the target voltage functions according to the figures 4 to 6 corresponds.

The third wire electrode 4, which is supplied from the first welding head 5a during a welding from point A to point B, is likewise operated with alternating voltage according to a voltage function according to ^FIGS . 4 to 6. The voltage functions of the trailing wire electrodes 4 (welding heads 5b and 5a) can be controlled so that the holding time of the last in the direction of the welding electrode 4 coincides with a maximum of leading directly in the welding direction wire electrode 4.

When the welding direction is reversed from point B to point A, the first welding electrode 4 leading to the welding direction is fed to the first welding head 5a. In this case, this welding electrode 4 is operated with direct current and the respective trailing welding electrodes 4 with an alternating current, which has a voltage function according to the figures of Figures 4 to 6.

Reference sign list

1 multi-electrode arrangement

 2 guide tube

3 nozzle

 4 wire electrodes

 5a first welding head

 5b second welding head

 5c third welding head

6 welding track

 7 Primary side of the welding power generator

8 Secondary part of the welding power generator

9 control

 10 microprocessor

11 function generator

 12 ideal switch

 13 Clamp for workpiece

 14 Terminal for wire electrode A point A

 B point B

 T period / period

t _h hold time

Claims

claims 1. A method for welding seam joints on metal components using a multi-electrode arrangement (1) with at least two welding electrodes (4), which are arranged one behind the other in a welding direction, wherein the welding electrodes ^¬ (4) of the multi-electrode arrangement (1) at the same time a common melt bath wherein the method comprises controlling the welding current of each welding electrode (4), the first welding electrode (4) being operated with direct current or alternating current or three phase alternating current and at least one second alternating welding current electrode (4) following in welding direction wherein the voltage of the second welding electrode (4) is held at least once during each period over a specified ^differently bene holding time at a voltage which is at most 50% is operated, preferably at most 20% of the maximum magnitude of the voltage of the first or second welding electrode (4 ) is. 2. The method according to claim 1, characterized in that the voltage of the second welding electrode (4) is held after each half period for a predetermined holding time at a voltage which is at most 50%, preferably at most 20% of the maximum amount of the voltage of the first or second welding electrode (4). 3. The method according to claim 1 or 2, characterized in that the second welding electrode (4) is operated with a pulsed alternating voltage ^¬ . 4. The method according to any one of claims 1 to 3, characterized in that the AC voltage of the second welding ^¬ electrode (4) by means of a function generator (11) is modulated. 5. The method according to any one of claims 1 to 4, characterized in that a desired voltage function for the alternating current ^¬ characteristic of the second welding electrode (4) is specified and nachge ^¬ by means of a function generator (11) control electronics of a welding power generator. 6. The method according to any one of claims 1 to 5, characterized in that the second welding electrode (4) is operated with a single-phase AC voltage. 7. The method according to any one of claims 1 to 5, characterized in that the second welding electrode (4) is operated with a three-phase AC voltage. 8. The method according to any one of claims 1 to 7, characterized in that the multi-electrode assembly (1) comprises at least three welding electrodes (4), wherein a third or more trailing in the welding direction welding electrode (4) at least once during each period, preferably after each half-period is maintained at a voltage over a predetermined dwell time which is at most 50%, preferably Hoechsmann ^¬ least is 20% of the amount of the maximum voltage of the respective welding electrode (4). 9. The method according to claim 8, characterized in that the holding time of the third or further welding electrode (4) coincides with a maximum of the voltage of each anticipating in the welding direction, preferably immediately adjacent welding electrode (4). 10. The method according to any one of claims 1 to 9, wherein the seam of the workpiece is added in multiple layers, wherein a first layer in a first welding operation in a first welding direction and a second layer with the same multi-electrode The arrangement (1) is generated in a second welding direction, wherein the first and the second welding direction are different from each other and wherein in a reversal of the welding direction each switching of the energization of the first and the trailing welding electrode (4) from AC to DC or vice versa takes place. 11. The method according to any one of claims 1 to 10, as a method for submerged arc welding, using an array of welding heads (5a, 5b, 5c9 for providing the welding electrodes (4), wherein the welding electrodes (4) as wire or tape electrodes ( 4) are formed. 12. Apparatus for welding seam joints on metal Components comprising a multi-electrode arrangement (1) having at least two welding electrodes (4) arranged in a welding direction one behind the other, wherein the welding ^¬ electrodes (4) of the multi-electrode arrangement (1) at the same time generate a common molten bath, at least one welding current generator with means for Controlling the welding current of each welding electrode (4), wherein the first welding in the welding direction (4) is energized with DC or AC or three-phase alternating current and at least a second in the welding direction trailing welding electrode (4) is energized with alternating current and the welding current generator is designed so that the voltage of the second welding electrode (4) at least once during each period can be maintained over a specified ^differently bene holding time at a voltage which is at most 50%, preferably at most 20% of the maximum Betra- ges the voltage of the first or second welding electrode (4). 13. The device according to claim 11, characterized in that the means for controlling the welding current comprise at least one microprocessor with a function generator.