WO2000024543A1

WO2000024543A1 - Welding method using a laser beam method in combination with two mig methods and device for carrying out said method

Info

Publication number: WO2000024543A1
Application number: PCT/EP1999/008051
Authority: WO
Inventors: Ulrich Dilthey; Uwe Reisgen; Armin Wieschemann
Original assignee: Ulrich Dilthey; Uwe Reisgen; Armin Wieschemann
Priority date: 1998-10-24
Filing date: 1999-10-25
Publication date: 2000-05-04
Also published as: DE19849117A1; DE19849117B4

Abstract

The invention relates to a welding method using a laser beam method in combination with two MIG methods. The aim of the invention is to provide a method and a corresponding device with which large gap widths in thick metal sheets (1) can be bridged. To this end, the two MIG methods are variably and independently carried out with respect to their respective position to the laser beam (7) and their respective adjustments and process parameters and their position in relation to each other. At the same time, components of the entire method are introduced into the welding method in such a manner that the two light arcs interact with the laser beam (7) to produce a common plasma.

Description

Welding process using a laser beam process together with two MSG processes and device for carrying out the process

The present invention relates to a welding method according to the preamble of claim 1 and an apparatus for carrying out the method according to the preamble of claim 6.

Such a welding method is known from DE-Ul-296 06 375. In a first exemplary embodiment, wire is fed to the process via a separate wire feed, which wire is melted by the laser beam directly or in the weld pool on the workpiece surface.

This procedure uses a significant proportion of the precious laser energy to melt the supplied wire.

This leads to a loss of possible feed speed.

The disclosure there also suggests the combination of the laser head with an arc welding device in connection with a protective gas atmosphere. However, this idea is based on the focusing of the laser beam and the arc in the common point of action. thats why

ERSATZBUVTT (RULE 26) the laser head is fixed to a common welding head together with the arc welding device.

Furthermore, a further variant with a second welding filler device is disclosed, which can also be understood as a pure cold wire feed. In this case, too, the energy required for melting the cold wire supplied must be diverted from the energy flow of the laser beam or the first arc and is therefore no longer available for generating the plasma.

In addition, this document also discloses a plurality of welding accessories which are attached to a common welding head in the form of an arc or plasma welding torch with or without an inert gas supply and are moved together with the latter.

Here, the welding head, together with any two MSG processes, forms a single rigid unit that is maintained during operation.

This also applies to a welding process according to JP 60-106 688 A, since the positions of the different tungsten electrodes relative to one another cannot be changed there either.

In addition, the disclosure of this document is based on the wrong idea that the depth of penetration of the laser increases due to the arcs arising in front of and behind the laser beam.

Furthermore, a combined method of laser welding and MIG is known from US Pat. No. 4,507,514. The method disclosed there is based on the incorrect assumption that the burn-in depths of the laser can be added to the burn-in depth of the MIG arc. However, since there are interactions between the energy flows within the melting bath arise that lead to at least partial absorption of energy, this assumption should not be possible. With this method, however, the relative setting between the laser beam and the electric arc, once set, is always retained.

In all of these known methods, the bridging of larger gap widths is problematic, particularly in the case of thick sheets, since either the amount of welding wire required per unit of time is too small or, as in the case of JP 60-106 688 A, is not possible at all or because it is necessary to generate a the necessary large-sized melt pool cannot provide the necessary energy or because the processes within the plasma or melt pool are without possibilities to intervene.

It is therefore an object of the present invention to eliminate the above disadvantages and to provide a method and an associated device with which even large gap widths on thick sheets can be bridged.

This object is achieved by the invention with the features of claim 1 and claim 6.

The advantage of the invention is that the arc pressure, which acts on the jointly formed plasma, can be controlled or regulated multidimensionally according to time and place. The regulation can be done individually for each MSG process.

According to the invention, there is therefore a controlled use of the arc pressure to increase, among other things, the welding speed, the gap width that can be bridged and the welding depth, and to control the path energy. It is assumed that the arc pressure is proportional to the current strength of the respective MSG process.

Since the two MSG torches act on the common plasma from different directions, the arc pressure can be varied via the at least two MSG torches in the sense of a welding process that is almost independent of the sheet thickness and gap width.

However, this means that the arc pressure via the variably adjustable amperage on the one hand and via the geometrical conditions assigned to one of the MSG torches is the decisive influencing variable for the overall process.

All three processes work in a single process zone.

For this purpose, the three processes must be so close together locally that even a single weld pool is formed with the formation of a single plasma. Nevertheless, the arc parameters of the two MSG processes are independent of one another and thus allow the multidimensional influencing of plasma and molten pool.

The influencing takes place essentially contactlessly solely via the arc pressure, which can be varied according to location and time. The invention is therefore essentially based on the management of the MSG processes independently of one another. However, it is a hybrid process with multi-dimensionally variably adjustable arc printing.

With regard to the geometrical arrangement of the two MSG processes, the tendency of the individual arcs to incline towards the laser beam due to the electric fields would also have to be taken into account. In view of the common process zone, the burner arrangement can also be spatially small.

Since it is assumed in the following that the arc penetration is deeper than the so-called keyhole depth given corresponding process parameters, the coupled hybrid process according to this invention allows the welding speed and the welding depth to be increased under the conditions that occur with large gap widths - present on thick sheets.

A keyhole depth that is less than the arc penetration is therefore essential for this fundamental consideration.

It is therefore a question of the geometrical arrangement of the MSG burners, on the one hand, and, on the other hand, of the energy supplied in each case, which is applied to the common plasma via the MSG burners.

This is the only way to set the arc penetration so that it reproducibly goes deeper than the keyhole depth.

As a result of this measure, the welding speed increases with the welding depth, since a large part of the laser energy that is coupled in is no longer absorbed in the melt as before, but rather serves to melt the solid phase.

At the same time, the energy supply via the two MSG processes is significantly greater than via just a single MSG process, so that the amount of additional melt supplied to the melt pool per unit time can be increased. This results in the better bridging of large gap widths even with thick sheets. It must be assumed that the weld metal in the area of the seam root needs edges that abut against each other since the laser does not carry its own melted material. As a result of the common process zone with common plasma, a sufficient amount of molten material is made available to the laser via the MSG processes, so that on the one hand even thick sheets can be welded through to the opposite surface, while at the same time one up to from the common process zone the opposite side of the continuous weld seam grows.

On the other hand, since most of the laser energy is needed to generate and maintain the steam channel in a melt pool, this portion of the laser energy can no longer be used to increase the energy without the additional energy flows that are coupled into the common process zone via the two MSG processes Welding speed available. The increased degree of absorption of the laser energy in the melt is principally compensated for by the disproportionate supply of energy as a result of the second MSG process.

However, the laser energy is not used to melt the supplied wire, but rather for through-welding and thus for the even root connection of the weld seam on the opposite seam side.

Both MSG processes are operated independently of each other. In principle, the procedures can not be synchronized; the mutual sources are regulated separately.

Depending on the materials and sheet thickness involved, different types of arcs, different wire diameters and different wire materials can also be used and use different positions of the MSG torch with regard to the welding direction.

Are the MSG burners e.g. positioned perpendicular to the welding direction, the largest gap bridging can be achieved. If the burners are set piercing and leading to the laser beam, the oxide skin, e.g. when welding aluminum is relevant, break up in order to also be able to bridge large gap widths.

Due to the leading or trailing arrangement of the MSG burners, the weld pool is stretched both in the welding direction and transversely to the welding direction, so that in addition to reduced pore formation, large gap widths can also be bridged.

In addition, the total amount of wire required can be divided in terms of unequal feed speeds for the two MSG torches. This measure can be advantageous, for example, for connecting sheets of different thicknesses.

Furthermore, the melt can also be influenced metallurgically via various wire materials.

The method according to the invention is based on the coupling of the laser beam with at least two MSG burners. The method thus offers not only the known advantages that result from the combination of a laser beam with a MSG burner, but also an additional degree of freedom, which is also expressed in a spatially variable influence on the common process zone.

The invention does indeed require greater mechanical expenditure through the use of further MSG burners. This effort is offset by the following advantages: - Bridging significantly larger gap widths compared to the laser MSG process with its own MSG burner and compared to the laser beam process with additional wire;

- Significant increase in the welding speed and increase in the welding depth compared to the laser beam process with and without filler material with the same output power P ^L and compared to the laser MSG process with a MSG torch and compared to MSG arc processes with and without two-wire technology;

- Significant reduction in heat input - this minimizes the thermal load on the component due to reduced path energy compared to the laser beam process with filler material and compared to the laser MSG process with an MSG torch and with all conventional arc processes;

- Significant increase in the melting rate compared to the laser beam process with filler material, the laser MSG process with an MSG burner and compared to all conventional arc processes if no bath protection is provided;

- Better controllability of the melt and targeted influencing of the seam formation through variable arrangement and adjustment of the individual processes.

In addition to the increased process stability and energy coupling, other advantages relating to the separation of the arc processes are important, such as the division of the required filler material into two MSG processes. On the one hand, this causes the melt bath, which may be very wide, to be stretched or elongated, which prevents the melt from sagging and opens up the possibility of bridging larger gap widths. On the other hand, through targeted settings of all three welding processes, and this includes in particular the coordination of the leading and trailing MSG process, sheet metal connections at high speeds with different joint geometries

(Fillet weld, butt weld, etc.) and joint preparation in one layer and secure the bath without any defects.

It is essential for the method according to the invention that, in comparison to the laser MSG process with an MSG burner at the same current strength, the achievable melting performance of two thin wires is greater than in the case of a single thick wire with a comparable cross-sectional area, since the larger surface area with two thin electrodes, better energy coupling at the electrode-side arc starting point is guaranteed. For this reason, when using the laser beam process with two MSG torches, a higher welding speed can be achieved with reduced heat input.

Are wire speeds of 20m / min. or more necessary, e.g. with larger sheet thicknesses with appropriate joint preparation, you are usually within the limits of the performance of individual power sources. This is especially true at wire speeds of well over 20m / min. to. By using a second power source, wire speeds of 40m / min can be achieved. achieve, which greatly expands the range of applications and offers an alternative solution for a variety of welding tasks by the invention. Compared to the laser MSG process with a MSG torch, another advantage is the increase in the sheet thickness that can be fully welded in one layer by the second arc process, which is to be adjusted afterwards and which then contributes to filling up the joint with its filler material .

Furthermore, it is to be expected that the method according to the invention, in addition to the possible uses in the welding of Steel can also be used with other materials, such as aluminum and its alloys.

Decisive for the implementation of the method according to the invention is the arrangement of the individual welding torches on a preferably common machining head and this must allow the absolutely free positioning of the MSG torches relative to one another and the free positioning of the focusing unit of the laser beam in such a way that, depending on the application, there are variable distances between them the arcs and the focal spot of the laser beam can be adjusted. The processing head must take the following boundary conditions into account:

- Individual adjustability of the individual processes - Free positioning of the processes to each other

- modular construction

- compact dimensions, good accessibility

- Pivots of the MSG torch in the working point of the laser beam (optional) - Optical protection by Crossjet for blowing away the welding fumes, splashes, etc.

- Protection of the machining head by splash plate

- Process gas supply via burner nozzles and / or process gas nozzle - Reproducibility through scaled axis setting

The invention is explained in more detail below on the basis of exemplary embodiments.

Show it :

Fig. . 1 shows a first exemplary embodiment of the invention with two trailing MSG burners

Fig. . 2 representation of Fig.l from the perspective of line II-II

Fig. 3 shows a further exemplary embodiment of the invention with a leading and a trailing MSG burner Fig.4 A device for performing the method Fig.4a View of Fig.4 from the line IVa-IVa Fig.5 Representation of the economic aspects of the method according to the invention Fig.6a-c Cross-sectional images of the welds with different weld preparations

Fig.l shows a welding process using a laser beam process together with two MSG processes. A Y seam according to FIG. 6b is shown in the view along the line I-I. The feed speed is directed to the left. The laser beam is focused precisely in the vertical leg of the Y and ensures a common melting zone in the area of the joint edge of the two sheets. As can be seen from Fig. 2, two MSG processes run after the preceding laser beam. The two MSG processes are shown in the illustration. Fig.l one behind the other and are guided with respect to their respective arrangements for the laser beam and their respective settings and process parameters in their positioning to each other on the one hand variable and independent and on the other hand as individual components of the overall process so coupled into the welding process that the two arcs together with the laser beam generate common plasma.

The laser beam is aligned so that it practically reaches to the lower end of the vertical bar of the "Y". Therefore, the seam root of the jointly generated welding bead is just melted by the laser beam. However, it is to be expressly included in the invention if a very narrow, non-welded zone 4 is formed between the lower end of the seam root 2 and the underside 3 of the sheet 1 to be welded. What is essential is a distance a between the process zones of the two MSG processes and the process zone of the laser beam, which is so small that all three processes together produce a common plasma with a common weld pool.

Since the laser does not carry its own material, it is advisable with this Y-seam to guide the laser onto the mutually abutting edges of the closely adjacent sheets 1, 1 '. However, since there is a common process zone between the two MSG processes and the laser beam process, in which the arc pressure significantly influences the time course of the melt pool parameters, the two MSG processes can influence the weld pool three-dimensionally via their respective relevant arc pressure.

It is taken into account that in laser beam welding the energy transport between the laser beam source and the material takes place exclusively through the almost coherent radiation. The arc, on the other hand, transfers the heat of welding through a high electrical current that flows to the workpiece via an electrically conductive plasma state, also known as an arc column.

Laser radiation is suitable for different processing methods of different materials. The low input of energy into the material at high processing speeds is characteristic. As a consequence, laser beam welding leads to a comparatively narrow, heat-affected zone with a large ratio of weld depth to seam width. Laser beam welding is therefore characterized by a deep welding effect, while the gap bridgeability that can be achieved is small due to the small beam diameter. As a result, the electrical efficiency in this method is generally below 10%. In many cases, however, this is offset by the high welding speed due to concentrated heat input. In contrast, the arc welding process results in lower processing speeds due to the much lower energy density; the focal spot of the arc on the surface of the material is correspondingly larger than that of the laser beam. As a result, the seams are wider than in laser beam welding, so that the energy introduced and the gap bridging capacity are greater with a comparable weld depth. Arc technology therefore offers the advantage of high energy efficiency with low investment costs. However, since the welding depth is limited, the seam, which can only be produced using an arc welding process, is characterized by a low ratio of seam height to seam width. The arc welding process alone allows only low welding speeds in connection with the high thermal load on the component.

Since the development of modern arc sources has also resulted in a multitude of control technology options, the simultaneous use of arc welding processes with laser welding processes has produced synergistic effects, which has led to an increase in the degree of freedom during the welding process.

In the present process coupling, the laser beam (C0 ₂ -, Nb: JAG, diode laser etc.) and arc (MSG) act simultaneously in an interaction zone of plasma and melt and influence or support each other. The possibility according to the invention of variable settings and positioning of the two MSG processes and the laser beam process can therefore achieve synergy effects which at least partially compensate for the disadvantages of the respective other methods.

The invention also makes use of the knowledge that in the coupled process according to this invention the Arc supplies heat to the weld metal in the upper vicinity in addition to the laser beam, which gives the weld seam a cup-shaped shape. The mutual influencing of the processes can have different strengths and characteristics depending on the arc or laser process used and the process parameters. The thermal load on the component can be kept low. Depending on the selected ratio of the power contributions, the laser or arc character can predominate.

Due to the variable and independent setting of the process parameters and the positioning of the MSG processes, the arc welding process can significantly increase the gap bridging ability. This results in the possibility of significantly increasing the tolerance range for edge preparation. In addition, the energy input of the arc into the processing volume also allows the cooling conditions to be controlled. Via the ionized plasma, the laser beam facilitates the ignition of the arc, stabilizes the arc welding process and energy deposition in the material depth. A greater welding depth or speed is therefore achieved by improving the energy coupling. It is thus possible to increase performance and energy efficiency without having to forego the advantages of using filler material, so that e.g. the structural structure can be influenced metallurgically.

Furthermore, the thermal load on the component is reduced by a significant reduction in the path energy compared to all known welding processes in which filler metal is used. Therefore, the thermally induced component distortion and possibly the internal stresses in the component after welding are significantly reduced. In addition, due to the larger tolerance range with regard to the quality of the edge preparation, the effort for the component preparation by mechanical processing of the edge geometry trie, by tensioning and stapling, as well as for the subsequent thermal straightening operation.

This applies in particular to large pieces of sheet metal and high welding speeds, since this limits the weldable sheet thicknesses for butt joints with a gap (I, Y, V seam etc.) or for fillet welds with a gap (HV, HY, DHY seam, etc. .) is canceled or significantly shifted upwards by the laser power and the intensified weld pool of the two MSG processes. Since with the addition of more filler material via the further MSG process, additional energy is also supplied to the common weld pool and the common plasma, the weldable sheet thickness can be higher.

Furthermore, in the case of butt joints (I, V, Y seam), the gap bridging ability depends on the size of the weld pool. As a result of the enlarged melt pool dimensions, larger melt pool volumes can therefore be realized, so that the known problems such as seam collapse, seam sag, penetration notches or pore lines are avoided even with large gaps to be bridged. This also applies to fillet welds where the gap bridging ability is limited by the maximum permissible weld pool size depending on the sheet thickness.

Furthermore, the welding speed can be increased both for butt welds and for fillet welds, since this is limited by the permissible arc power for the same laser power. As a result of the arc power of the additional MSG process, the welding speed can therefore be increased.

Furthermore, since the material feed rate increases without increasing the wire feed speed V ^D as a result of the second MSG process, the consequences of excessive wire speed, such as seam sinking, penetration notches or seam sag, are reliably avoided. 3 shows an embodiment with a leading MSG process 5, a trailing MSG process 6 and a laser beam process 7. It is also important here that the two arcs of each MSG process generate a common plasma together with the laser beam, and that the arc pressure of the two MSG processes is variable and independent of one another based on the respective settings and the process parameters and the positioning of the MSG torches.

At the same time, however, all components of the overall process are coupled into the welding process in such a way that the two arcs together with the laser beam generate a common plasma.

4 shows a preferred embodiment of a processing head for a laser beam process and two MSG burners.

The two MSG burners are adjusted to each other and to the laser beam using a total of ten axes. Two axes, a vertical rotatory axis ® and a vertical translatory axis serve to position the MSG torch together in relation to the laser beam. In this way it is possible, for example, to use the ® axis to arrange one MSG burner in the leading function and the other MSG burner in the trailing function to the laser beam. In this arrangement, the distance between the wire tip and the focal point can be varied within the range required for the method. A rotation of the axis ® from this position by 90 degrees leads to an arrangement of the MSG torch perpendicular to the welding direction and thus enables welding with two leading or trailing MSG torches, depending on the welding direction. With the vertical axis ® it is initially possible to roughly position both MSG burners relative to the focal point of the laser beam according to the focal length used. With four of each of the remaining eight axes, the individual MSG burners can be adjusted exactly to each other and to the laser beam. The axis ® represents the vertical inclined axis for translatory adjustment of the first MSG burner along its longitudinal axis. This also applies analogously to the axis © with respect to the second MSG burner. The axes ® and © provide two rotary axes. These arc-shaped axes are used for rotary adjustment of the first MSG burner so that the fulcrum coincides with the focal point of the laser. The axis © lies horizontally and is used for the rotary adjustment of the first MSG burner, the pivot point penetrating the adjustment arch of the axis ® vertically. This also applies to the axes ® and ® for the second MSG burner.

In addition, the axes ⁽ D and ® are provided for translational adjustment of the first and second MSG burner.

Corresponding scaling ensures a reproducible setting for all axes.

The rotatory axes ® and ® are used to adjust the first and second MSG torches along a vertical arc that is centered at the focal point of the laser beam. The fulcrum of the adjustment therefore coincides with the focal point of the laser. It is therefore possible to vary the entry angle of the MSG arcs into the workpiece or their inclination to the (vertical) laser beam via these axes.

With the horizontal axes © or ® for rotary adjustment of the first or second MSG torch, the MSG torch can be moved further from the focal point of the, depending on the position of the axis ® to the side or in the welding direction Guide the laser away or bring it closer to it. The pivot points of the axes © and ® penetrate the adjustment arch of the axis ® vertically.

With the two horizontal axes ® and ®, the first and the second MSG torch can also be translationally moved further away from the focal point of the laser or closer to it, again depending on the position of the axis ® laterally or in the welding direction .

The adjustable axes are e.g. with setting or

Locking screws with fine thread, possibly micrometer screws. Of course, it is also possible to use more complex numerically controlled stepper motors or the like instead of manual drives.

The processing head thus allows both welding torches to be positioned in a reproducible manner in almost any arrangement with respect to the laser beam. Each wire of each MSG burner is connected to its own power source, which can be controlled separately, and is guided by its own wire feed system to the common processing head. The arcs create a common plasma and a common weld pool with the laser beam at a small distance. In addition, it can be provided that the adjustment range of the MSG burner to the laser beam is so large that separate melting baths are also created in order to use this device to carry out the conventional laser MSG process without a common melting bath and without a common plasma.

6a-c show different weld preparations.

Regardless of the respective weld preparation, the process according to this invention allows welding through even with large sheet thicknesses to the opposite achieve overlying sheet metal surface, the seam width on the sheet metal side where the welding torches sit goblet-shaped increases towards the outside, while the respective laser beam leads to welding through to the seam root, which also has a good connection to the adjacent sheet metal zones there.

Reference list

Sheet metal 'sheet seam underside zone leading MSG burner trailing MSG burner' trailing MSG burner laser beam seam root distance

Claims

claims

. Welding process under execution of a laser beam process together with two MSG processes, characterized. that the two MSG processes with regard to their respective arrangements for the laser beam as well as their respective settings and process parameters and their positioning with respect to one another are performed variably and independently of one another and, on the other hand, are coupled into the welding process as individual components of the overall process in such a way that the two arcs generate a common plasma together with the laser beam.

2nd Welding method according to claim 1, characterized in that at least one MSG process precedes and at least one MSG process runs.

3. Welding method according to claim 1, characterized in that all MSG processes are running.

4. Welding method according to claim 1, characterized in that all MSG processes run.

5. Welding method according to one of the preceding claims, characterized in that at least one of the MSG processes can be replaced by a plasma MSG process.

6. Device for carrying out the method according to any one of the preceding claims, characterized by a processing head with a laser beam unit and with at least two MSG burners arranged next to the laser beam unit so that the processing zones of the laser beam unit and the MSG burner essentially coincide.

7. The device according to claim 6, characterized in that two MSG burners are provided.

8. The device according to claim 6 or 7, characterized in that the MSG burners are adjustably mounted in at least one of the following axes:

Axis ®: vertical axis for rotary adjustment and joint positioning of the MSG torch to the laser beam;

Axis ®: vertical axis for translatory adjustment and joint positioning of the MSG torch to the laser beam;

- Axis ®: axis inclined to the vertical for translational adjustment of the first MSG burner along its longitudinal axis;

MSG burner along its longitudinal axis;

Axis ®: Arc-shaped axis for the rotary adjustment of the first MSG burner, the fulcrum coinciding with the focal point of the laser; Axis ®: Arc-shaped axis for rotary adjustment of the second MSG burner, the fulcrum coinciding with the focal point of the laser;

Axis ©: horizontal axis for rotary adjustment of the first MSG burner, the pivot point penetrating the adjustment arch of the axis ® vertically;

Axis ®: horizontal axis for rotary adjustment of the second MSG burner, the pivot point penetrating the adjustment arc of the axis ® vertically;

Axis ®: horizontal axis for translational adjustment of the first MSG burner;

Axis ®: horizontal axis for translatory adjustment of the second MSG burner.

9. The device according to claim 8, characterized in that the MSG burners are mounted adjustable in all axes.

10. The device according to claim 8 or 9, characterized in that all axes have a scaling.

11. Device according to one of the preceding claims, characterized in that the process gas is supplied via the MSG burner and / or at least one process gas nozzle.

2. Device according to one of the preceding claims, characterized in that crossjets are provided to protect the optics.