Welding method and welding apparatus

Abstract

A corresponding welding apparatus 1 having a welding method and a heat source 4 and a welding filler as a welding wire 8 is proposed. By using the welding method and the welding apparatus 1, a welding quality that is as high and uniform as possible can be achieved easily and without depending on the skill of the welder. According to the present invention, the welding wire 8 is fed into the molten pool 26 in an intermittent feeding cycle C, preferably with a reversing feeding speed v, and during the execution of the welding method, the actual value t1_ist of the time interval t1 of the first period Z1 of the feeding cycle C in which the welding wire 8 is not in contact with the molten pool 26 is measured, and / or the actual value t2_ist of the time interval t2 of the second period Z2 of the feeding cycle C in which the welding wire 8 is in contact with the molten pool 26 is measured, and it is proposed that at least one parameter of the feeding speed v of the welding wire 8 is changed depending on the actual value measured during the feeding cycle C and a preset target value.

Description

Technical Field

[0001] The present invention relates to a welding method in which energy is applied by a non-consumable electrode as a heat source within a region of a welding location on a work piece to form a molten pool, a welding wire independent of the heat source is fed into the molten pool, and the welding wire is melted within the region of the molten pool by the energy applied to form a weld joint on the work piece. Further, the present invention relates to a welding apparatus including a welding torch having a non-consumable electrode as a heat source for applying energy to a welding location on a work piece to generate a molten pool, a feeding device for feeding a welding wire independent of the heat source into the molten pool, and a control device for controlling the feeding device, wherein the welding wire is meltable within the region of the molten pool by the energy applied from the heat source to form a weld joint on the work piece.

Background Art

[0002] Including, the present invention relates to such a welding apparatus including a welding apparatus having a heat source for applying energy to a welding location on a work piece to form a molten pool. In this case, independent of the heat source, a separate additive is fed into the molten pool as a welding wire. Similarly, to form a weld joint on the work piece, the welding wire is melted by the energy of the heat source. Examples of this are, for example, known TIG welding (tungsten inert gas welding) in which a non-consumable electrode made of tungsten or a tungsten alloy is used as a heat source, similarly known plasma welding in which a non-consumable electrode is used, or known laser welding in which a laser optical device is used as a heat source.

[0003] In the case of TIG welding, an arc is generated between the electrode and the workpiece. By means of this arc, on the one hand, a molten pool is formed on the workpiece and, on the other hand, the welding wire is melted. In the case of laser welding, a laser beam is generated by a laser optical device, a molten pool is formed by the laser beam, and the fed welding wire is melted. A combination consisting of TIG welding and laser welding is also known and is called TIG / laser hybrid welding.

[0004] In this case, the molten pool is generated, on the one hand, by the energy of the arc and, on the other hand, by the energy of the laser beam. In all cases, the filler material is fed separately as a welding wire. Generally, this feeding is carried out by a feeding device.

[0005] A welding method using a consumable electrode in which the welding wire is used directly as an electrode, such as known MIG / MAG welding, can be distinguished from the above welding methods. In this case, no separate filler material is required and the electrode simultaneously forms the welding wire. This method is not included in the present invention.

[0006] In the case of TIG welding, a welding current is passed through the electrode in order to form and maintain an arc between the electrode and the workpiece. In order to avoid contact between the molten part and the surrounding air, an inert shielding gas (usually argon or helium) is generally also used. Furthermore, a heating current may be passed through the welding wire in order to electrically heat the welding wire and promote melting of the filler material.

[0007] In many cases, the welding wire is fed to the welding location by a feeding device. In this case, generally, a preset or settable, mostly constant value is used for the feeding speed. This value may depend on the value of the welding current set in some cases. However, in this case, it frequently occurs that the welding wire is immersed too deeply in the molten pool or the welding wire moves too far away from the molten pool without contacting it. In both cases, as a result, the welding quality deteriorates and may cause a non-uniform weld joint or a defect in the weld joint. This occurs especially when the welding torch is manually operated. This is because a predetermined influencing parameter that affects the energy acting on the welding wire cannot always be accurately maintained by the welder. For example, the distance from the welding torch to the workpiece or the angle between the welding wire and the electrode is included in the influencing parameter. For example, in the case of welding with a more complex geometric structure and / or when the welding speed is different, such defects may occur even when a robot operates the welding torch.

[0008] To solve this problem, it is already known from WO 2010 / 082081 to detect a change in the voltage between the welding wire and the workpiece using a heating current that energizes the welding wire. When the voltage exceeds a preset limit value, the heating current is reduced to a very small value for a predetermined period to avoid rapid melting of the welding wire. A new contact between the welding wire and the workpiece (exactly, the molten pool) is detected by the remaining small heating current. In such a case of contact, a short circuit occurs. As a result, the voltage between the welding wire and the workpiece becomes zero. When a new contact is confirmed, the heating current energizing the welding wire is increased again. Therefore, this method can only be used for hot wires (where the welding wire is further heated by the heating current), but not for cold wires (not by such a heating current).

[0009] In Japanese Patent Publication No. 60-36860, in order to change the position of the welding wire relative to the workpiece, the potential generated around the electrode is evaluated. The potential can be measured as the voltage between the welding wire and the workpiece, and can be used to derive the immersion position of the welding wire into the molten pool from the measurement. Therefore, in order to set the optimal immersion position, the position of the welding wire relative to the workpiece, precisely the distance from the welding wire to the workpiece, is controlled. This method is based on the fact that the molten pool and the welding wire are always in contact. However, in reality, the welding wire and the workpiece are always in contact, and the detectable voltage is very small and within a very narrow range. As a result, this method is sensitive to the influence of disturbances and has low reliability. Moreover, In order to adjust the position of the welding wire relative to the workpiece and the welding torch, additional controllers and actuators are required.

[0010] Furthermore, U.S. Patent Application Publication No. 2020 / 246902 relates to a MIG / MAG welding method in which the sum of a plurality of periods is changed during welding. However, since this method is a MIG / MAG welding method, it does not sufficiently address the problems specific and unique to the TIG welding method.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0012] An object of the present invention is to provide a welding method and a corresponding welding apparatus having a heat source and a welding filler as a welding wire, which can achieve a welding quality as high and uniform as possible easily and without depending on the skill of a welder.

Means for Solving the Problems

[0013] According to the present invention using the above welding method, this problem is solved by feeding the welding wire into the molten pool in an intermittent feeding cycle, preferably with a reversing feeding speed, and during the execution of the welding method, measuring the actual value of the time interval of the first period of each feeding cycle in which the welding wire is not in contact with the molten pool, and / or measuring the actual value of the time interval of the second period of each feeding cycle in which the welding wire is in contact with the molten pool, and changing at least one set parameter of the feeding speed of the welding wire depending on the actual value measured during the feeding cycle and a preset target value. Preferably, the overall average feeding speed of one feeding cycle and / or the positive average feeding speed of one feeding cycle and / or the negative average feeding speed of one feeding cycle are used as parameters of the feeding speed. In this case, one feeding cycle consists of a first period having a positive feeding speed of the welding wire and a second period having a subsequent zero or negative feeding speed. Therefore, according to the welding method of the present invention, the parameters of the feeding speed can be continuously adjusted in order to adjust the target value. Thereby, a uniform welded joint having high quality can be formed with little influence from the above changing parameters. Some of the above parameters may be changed.

[0014] According to the present invention, the time interval of the first period of each feeding cycle is measured as an actual value, and the target value for this first time interval is used as a target value. Or, the time interval of the second period of each feeding cycle is measured as an actual value, and the target value for this second time interval is used as a target value. Or, the total consisting of the time interval of the first period and the time interval of the second period of each feeding cycle is measured as an actual value, and the target value for the droplet detachment frequency is used as a target value. For example, when it is confirmed that the actual time interval of the first period is longer than a preset target value, in order to adjust this target value, the parameter of the feeding speed of the welding wire is changed. For example, the average feeding speed can be changed, especially increased, for each cycle, or the positive average feeding speed can be changed, especially increased, for each cycle. Conversely, for example, when it is confirmed that the actual time interval of the first period is shorter than a preset target value, the average feeding speed or the positive average feeding speed of the welding wire is decreased. Thereby, it is possible to maintain the time interval of the first period when the welding wire is not in contact with the molten pool to be substantially constant over the entire welding method. Naturally, instead of the first period, the second period when the welding wire is in contact with the molten pool may be used. This second period substantially corresponds to the period existing between two consecutive first periods. The total consisting of the time interval of the first period and the time interval of the second period (which corresponds to the droplet detachment frequency) may be used.

[0015] For example, at the start of each feeding cycle, the feeding speed for a set boost period is set to a predetermined first value, and after the elapse of the boost period, it is decreased from the first value to a predetermined second value, whereby the average feeding speed or the positive average feeding speed can be changed. In this case, the first value, and / or the ratio between the first value and the second value, and / or the length of the boost period can preferably be set depending on the error between the measured actual value and the preset target value. Thereby, the average feeding speed or the positive average feeding speed can be easily changed, and the undesirable effect caused by the inertia of the welding wire can be beneficially reduced.

[0016] Preferably, energy is applied to the work piece via an electric arc generated between the non-consumable electrode and the work piece. For this reason, the present invention can be used in known WIG welding. Alternatively or additionally, energy may be applied to the work piece by a laser beam generated from a laser optical device. Thereby, the present invention can be used in laser welding methods or laser hybrid welding.

[0017] The actual value of the time interval of the first period and / or the actual value of the time interval of the second period are measured continuously or intermittently. For example, intermittent detection can be performed in the time steps of the control described below. Thereby, continuous detection is not required.

[0018] Preferably, a preset target value is adjusted by changing at least one parameter of the feeding speed. For this reason, feedback control can be used. Thereby, a very accurate adjustment of the target value becomes possible. Therefore, a uniform welding quality can be achieved without being affected by disturbances.

[0019] For example, the target value can be set depending on the diameter of the welding wire and / or the material of the welding wire and / or the electrical welding parameters, particularly the welding current and / or the shape of the joint of the welded joint. Therefore, various influencing parameters can be considered when selecting the target value. For this reason, the method can be flexibly adapted to predetermined conditions. The target value can be set by the welder, for example via a user interface, or selected from existing values.

[0020] Preferably, the potential is taken out with the welding wire, and the actual value of the time interval of the first period and / or the actual value of the time interval of the second period are obtained from the time evolution of the taken-out potential. Thereby, it can be easily detected how long and when the welding wire is in contact with the work piece.

[0021] For example, a measurement voltage between the welding wire and the workpiece and / or a measurement current passed through the welding wire are measured, and the actual value of the time interval in the first period and / or the actual value of the time interval in the second period are obtained from the measurement current and / or the time change of the measurement current, whereby the potential can be extracted. A ground potential where the potential exists around the welding wire may be formed between the welding wire and the workpiece.

[0022] Furthermore, according to the welding apparatus described above, the problem of the present invention is that the control device is configured to operate the feeding device so that the welding wire can be supplied to the molten pool in an intermittent feeding cycle, preferably with a reversing feeding speed. During the welding method executed by the welding apparatus, the measuring device is configured to measure the actual value of the time interval in the first period of each one feeding cycle in which the welding wire is not in contact with the molten pool, and / or the actual value of the time interval in the second period of each one feeding cycle in which the welding wire is in contact with the molten pool. The control device is configured to operate the feeding device so as to change at least one set parameter of the feeding speed of the welding wire depending on the actual value measured during the feeding cycle and a preset target value.

[0023] Preferred configurations of the welding apparatus are described in claims 10 to 14.

[0024] Hereinafter, the present invention will be described in detail with reference to FIGS. 1 to 4 showing exemplary, schematic and non-limiting preferred configurations of the present invention.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0026] In FIG. 1, the welding apparatus 1 is shown as a TIG welding apparatus. The welding apparatus 1 has a welding power source 2 and a welding torch 3. A heat source 4 is disposed in the welding torch 3 as a non-consumable electrode 4a, for example, a tungsten electrode. However, within the scope of the present invention, instead of or in addition to the non-consumable electrode 4a, the heat source 4 may have a laser optical device (not shown). However, for simplicity, hereinafter, the present invention will be described exclusively based on TIG welding. Of course, laser welding or the TIG / laser hybrid welding described at the beginning can also be used in the same manner.

[0027] In the illustrated example, the welding torch 3 is connected to the welding power source 2 by a hose cable 5. Further, a shielding gas cylinder 6 is provided. A general container valve for adjusting the flow rate of, for example, the shielding gas in the shielding gas cylinder 6 is not shown. Further, a feeding device 7 is provided to supply the welding wire 8 as a welding additive to the welding location 25. The feeding device 7 may be part of the welding power source 2, but may also be configured as an independent device. A welding wire spool 12 is disposed in the feeding device 7. The welding wire 8 is fed out from the welding wire spool 12 during welding and supplied to the welding location 25 at a feeding speed v. To generate the feeding speed v, the feeding device 7 has a suitable and sufficiently high-performance driving device 7a.

[0028] Furthermore, a control device 13 for controlling the welding device 1 is provided. Within the scope of the present invention, the control device 13 is at least configured to operate the feeding device 7, particularly the drive device 7a, to set the feeding speed v of the welding wire 8 to a desired value. Within the scope of the present invention, as will be further described in detail below with reference to FIG. 3, the welding wire 8 is supplied to the welding location 25 in an intermittent feeding cycle. In this case, the feeding cycle C has a first period presenting a positive feeding speed v and a second period Z2 presenting a zero feeding speed or a negative feeding speed (during reverse wire feeding). As is known, the control device 13 can have appropriate hardware and / or software. However, preferably, the control device 13 is also configured to control the welding method executed by the welding device 1. Therefore, in addition to controlling the feeding speed v, the control device 13 can also perform open-loop control or closed-loop control on the welding parameters of the welding process being executed, such as the welding current Is, the welding voltage Us, the frequency of the welding current Is or the welding voltage Us, the amount of shielding gas supplied, etc. Of course, a plurality of independent control devices communicating with each other via an appropriate communication link may be provided to exchange control variables. However, for the present invention, the control of the feeding speed v is important. Therefore, below, the description will mainly focus on the control device 13 only.

[0029] The welding device 1 may also be provided with a user interface 14 that communicates appropriately with the control device 13. The welder can select, via the user interface 14, a predetermined welding process having, for example, a welding program or preset welding parameters (e.g., an impulse welding process having a predetermined welding current Is and a predetermined frequency). Also, specific settings can be manually selected or changed. For example, conventionally, the feeding speed v of the welding wire 8 has generally been preset by the welder or selected from available values and has usually been constant.

[0030] Through the hose cable 5, all necessary media, energy, and control signals can be sent to the welding torch 3, such as electrical energy (current, voltage), cooling medium (if the welding torch 3 is cooled), control wires for controlling the welding process, shielding gas from the shielding gas cylinder 6, or the welding wire 8. Generally, a hose is provided as the hose cable 5. Individual pipes and media are passed through this hose. However, of course, a plurality of separate hoses or pipes may be provided.

[0031] The counter electrode (usually the positive electrode) is in contact with the workpiece 10 to be welded via the contact conductor 9. In many cases, the contact conductor 9 is also called the grounding wire. To enable the welding wire 8 to be fed to the electrode 4a at the welding location 25 in the desired position and direction, a welding wire feed tube 11 may be arranged on the welding torch 3. The welding wire feed tube 11 may be connected to the welding wire tube 22. The welding wire 8 is individually guided through the welding wire tube 22, that is, from the outside of the hose cable 5 to the welding wire feed tube 11. However, the welding wire feed tube 11 does not necessarily have to be arranged on the welding torch 3 and may be arranged at any other suitable location, such as on a welding robot. The feeding device 7 also does not necessarily have to be arranged on the welding power source 2 and may be arranged at any other suitable location, such as on a welding robot.

[0032] Generally, a contact sleeve (not shown) is disposed on the welding torch 3. The contact sleeve surrounds and is in electrical contact with the electrode 4a and is usually connected to the welding power source 2 (usually the positive electrode) via the welding current line 24 laid in the hose cable 5. The electrode 4a projects from the welding torch 3 at the end of the welding torch 3. Shielding gas that surrounds the welding location 25 having the molten pool 26 (as shown in FIG. 3) and shields it from the ambient atmosphere can flow out from the welding torch 3 around the electrode 4a. The welding wire 8 is supplied to the welding location 25 at an intermittent feed cycle C (optionally by reverse wire feeding) during welding. Reverse wire feeding means that a positive feed rate is applied during the first period Z1 and a negative feed rate is applied during the second period Z2. Since the basic configuration and basic functions of such a welding apparatus 1 and various variations thereof are known, they will not be described in detail here.

[0033] As already explained, instead of or in addition to the illustrated electrode 4a, a laser optical device (not shown) may be provided as the heat source 4. In this case, in addition to or instead of the arc 27 (see FIG. 2), heat is applied to the workpiece 10 by the laser beam. In the case of pure (i.e., without using the electrode 4a) laser welding, the wires 24, 9 are not necessary as is known. This is because there is no need to strike an arc. Nevertheless, the configuration of the welding apparatus 1 is basically the same. In particular, even in the case of laser welding, the welding wire 8 is fed to the welding location 25 by the feeding device 7.

[0034] Figure 2 shows in detail the welding torch 3 within the region of the tip of the non-consumable electrode 4a existing at the welding location 25 on the workpiece 10. To strike or maintain the arc 27 between the electrode 4a and the workpiece 10, a welding current I_s (e.g., within the range of 100 A) that is energized to the electrode 4a via the welding wire 24 is generated from the welding power source 2. To strike the arc 27, known methods, such as high-frequency arc striking or arc striking by bringing the workpiece 10 into contact with the electrode 4a and then lifting the electrode 4a, can be used. When the current I_s energizes the electrode 4a, as shown in Figure 2, a substantially static electric field 28 is formed around the electrode 4a as is known.

[0035] This substantially static electric field 28 causes a potential distribution around the electrode 4a as illustrated by the equipotential lines 28a in Figure 2. Basically, the value depends, among other things, on the welding current, cooling of the electrode, shielding gas, arc length (distance A), etc., but can be regarded as known. The potential P can be detected as an electrical variable, for example, by a suitable potential detection device 30 as the measured voltage U_m or as the measured current I_s. For this purpose, the potential detection device 30 can have, for example, a voltmeter 29. The measured voltage U_m can be taken with respect to the reference potential by the voltmeter 29. In Figure 2, the voltage values with respect to the potential P of the workpiece 10 are illustrated by the equipotential lines 28a. This potential P is fed to the welding power source 2 and is thus taken out via the welding wire 8 existing within the substantially static electric field and detected by the voltmeter 29. For this purpose, it is not necessary to energize the welding wire 8 with a specific measurement current. Also, the heating current that can heat the welding wire 8 hardly interferes with the detection of the potential P. Therefore, the potential P can be taken out both when using a cold wire and when using a hot wire.

[0036] As illustrated in FIG. 3, instead of the measurement voltage Um, the measurement current Im resulting from the potential P, which energizes the welding wire 8, can likewise be measured. For this purpose, for example, the terminal resistance 34 can be connected between the welding wire 8 and the work 10. The current that can be measured to detect the potential P as the measurement current Im flows through the terminal resistance 34. In this case, as shown in FIG. 3, the potential detection device 30 has a suitable ammeter 33. However, of course, instead of the measurement current Im and the measurement voltage Um, another electrical variable related to the potential distribution may likewise be detected or calculated. For example, the resistance or power may be calculated from the measurement voltage Um and the measurement current Im. Therefore, within the scope of the present invention, all of these methods are included in the method of extracting the potential P.

[0037] As shown in FIG. 3, the potential detection device 30 can be arranged, for example, in the welding power source 2. In the welding power source 2, furthermore, the reference potential of the work 10 can be extracted, for example, via the contact conductor 9 for contacting the work 10 or the proprietary wiring. It is beneficial to use the contact conductor 9 because additional wiring can be omitted. When using the contact conductor 9, the potential detection device 30 can be connected, for example, to the terminal (ground connector) of the contact conductor 9 in the welding device 1. To detect the electrical variable indicating the potential P, for example, the measurement voltage Um, it is only necessary to additionally provide the potential detection device 30 in the welding device 1. For this reason, the electrical contact at the welding wire 8 can be easily realized, for example, as a sliding contact within the feeding device 7. In some cases, the terminal resistance 34, which may also be part of the potential detection device 30, can be provided between the welding wire 8 and the work or the contact conductor 9 or another reference potential.

[0038] Whether the welding wire 8 is in contact with the molten pool 26 formed by the arc 27 from the electrode 4a or whether the welding wire 8 is not too far separated from the molten pool 26 can be easily confirmed from the electrical variables (measured voltage U_m, measured current I_m, etc.) representing the potential P based on the generated potential distribution. When the welding wire 8 comes into contact with the molten pool 26, a short circuit occurs. As a result, the measured voltage U_m measured by the voltmeter 29 decreases to zero (or almost zero), or the measured current I_m measured by the ammeter 33 decreases to zero (or almost zero). The same also holds true for the variables derived therefrom. When the welding wire 8 is not in contact with the molten pool 26, on the contrary, a predetermined measured current I_m or a predetermined measured voltage U_m depending on the height of the potential P is measured.

[0039] To generate a predetermined reference potential, in some cases, an additional auxiliary power source (not shown) may be provided in the measurement circuit of the potential detection device 30. This is useful for application, for example, when no electric field is generated around the heat source 4 or only a weak electric field is generated, such as in the case of pure laser welding where the heat source is the laser optical device 4a. By using the auxiliary power source, measurable potentials that can be used for measurement are always available without depending on the potential P of the electric field. The auxiliary power source can be configured, for example, as a high-resistance voltage source. The auxiliary voltage can be applied by the high-resistance voltage source. Therefore, in the case of TIG welding, for example, even before the arc 27 is struck, the potential P can be detected, and whether the welding wire 8 is in contact with the workpiece 10, particularly whether a short circuit has occurred, can be confirmed based on the potential P.

[0040] According to the invention, a measuring device 31 is further provided which is configured to measure the actual value t1_ist of the time interval t1 of the first period Z1 (during which the welding wire 8 does not contact the molten pool 26 or the workpiece 10) of each feeding cycle C during the execution of the welding method. Alternatively or additionally, the measuring device 31 may be configured to measure the actual value t2_ist of the time interval t2 of the second period Z2 (during which the welding wire 8 contacts the molten pool 26 or the workpiece 10) of each feeding cycle C. The time intervals t1, t2 and the periods Z1, Z2 are shown in FIG. 4.

[0041] As shown in FIG. 2, the measuring device 31 can be configured as an independent device having suitable hardware and / or software and communicating with the control device 13 via a suitable communication connection. However, as shown in FIG. 3, preferably, the measuring device 31 is incorporated in the control device 13. According to the invention, in order to adjust at least one set parameter of the feed rate v of the welding wire 8 depending on the measured actual value t1_ist and / or a preset target value, the control device 13 is configured to operate the feeding device 7, in particular the drive device 7a.

[0042] Based on the potential distribution generated, it can be easily determined from the electrical variables (measuring voltage U_m, measuring current I_m, etc.) representing the potential P whether the welding wire 8 is in contact with (there is a short circuit) or not too far away from (there is no short circuit) the molten pool 26 formed by the arc 27 from the electrode 4a. In this case, as shown based on FIG. 4, the time interval t1 of the first period Z1 (without short circuit) or the time interval t2 of the second period Z2 (with short circuit) can be measured from the time course of the detected electrical variables representing the potential P.

[0043] In the upper diagram of FIG. 4, the time course of the detected potential P is illustrated. In this case, this course corresponds to the course of the actual value P of the potential P measured by the potential detection device 30. Depending on the variable to be measured, this course can be, for example, the course of the measured current Im or the course of the measured voltage Um. In the central diagram, the associated time course of the target value Psoll of the potential P is shown. In the lower diagram, the associated time course of the feed rate v of the welding wire 8 is shown. Thus, it can be seen that the welding wire 8 is fed into the molten pool 26 with a feed rate v that changes over time in an intermittent feed cycle C. The feed rate v is set to a predetermined positive value, here the values v1, v2, in each first period Z1 of each cycle C (in FIG. 4, for the sake of simplicity, only the first cycle C is shown). In the illustrated example, a feed rate v = 0 is used in the subsequent second period Z2 of the cycle C. Instead, as shown by the dashed line for two feed cycles C, a reversing wire feed may be used. In the case of this reversing wire feed, a negative feed rate v is used in each second period Z2. In this case, the negative feed rate corresponds to the retraction of the welding wire 8 away from the molten pool 26, and the positive feed rate v corresponds to the movement in the direction of the molten pool 26.

[0044] The welding wire 8 is not in contact with the molten pool 26 during each first period Z1. Therefore, the first period Z1 corresponds to a period without short circuit in which the potential P_ist measured by the potential detection device 30 is greater than zero or greater than a set value representing a short circuit. The second period Z2 existing between each of the two first periods Z1 corresponds to a short circuit period in which the potential P_ist measured by the potential detection device 30 is zero or takes a value representing a short circuit. The measuring device 31 can measure the actual time interval t1 of the first period Z1, that is, the length of the period without short circuit, from the trend P_ist of the actual value. Instead, the measuring device 31 can also measure the actual time interval t2_ist of the second period Z2, that is, the length of the short circuit period, from the trend P_ist of the actual value. The total time interval of the feeding cycle C may be measured. This corresponds to the sum of the time interval t1_ist of the first period Z1 and the time interval t2_ist of the second period Z2. This is also called the so-called droplet detachment frequency. In FIG. 4, the actual droplet detachment frequency f_ist and the desired target value f_soll of the droplet detachment frequency f are illustrated for one feeding cycle C.

[0045] For example, a predetermined threshold value P_sw representing a short circuit can be set for the potential P. The threshold value P_sw can be, for example, zero or a value slightly greater than zero. In FIG. 4, a threshold value P_sw slightly greater than zero is illustrated. For example, the actual value t1_ist of the time interval t1 can be measured by measuring the time between the point in time ZPa when the measured potential P_ist (for example, the welding current I_s or the welding voltage U_s) exceeds the set threshold value P_sw and the subsequent point in time ZPb when the measured potential P_ist newly falls below the set threshold value P. Similarly, the time t2 between the point in time ZPb when the measured potential P_ist falls below the set threshold value P and the point in time ZPc when the measured potential P_ist exceeds the set threshold value P_sw again can be measured. In the upper diagram of FIG. 4, these points in time ZPa-ZPc are illustrated for a first cycle consisting of a first period Z1 and a subsequent second period Z2. However, of course, the measurement is carried out continuously during the execution of the welding process, that is, for a large number of feeding cycles C. The actual value f_ist of the droplet detachment frequency f corresponds to the time between the point in time ZPa and the point in time ZPc.

[0046] In this case, preferably, the actual values t1_ist, t2_ist of the time intervals t1, t2 are measured continuously, but may also be measured discretely, i.e., at set specific intervals. That is, the measurement of the actual value P_ist, for example the measurement of the measured voltage U_m or the measured current I_m, is preferably also carried out continuously or discretely. The discrete detection can be carried out, for example, in the time steps of the control which will be explained in more detail below. In the central figure, it can be seen that a predetermined constant time t1_soll (or t2_soll) is preset as the target value. According to the invention, the control device 13 is configured to operate the feeding device 7 appropriately. As a result, at least one parameter of the set feeding speed v of the welding wire 8 is adjusted for each feeding cycle C during the welding process so that the desired target values t1_soll, t2_soll or f_soll are obtained.

[0047] For example, the overall average feeding speed vm of each one feeding cycle C and / or the positive average feeding speed vmZ1 of each one feeding cycle C and / or the negative average feeding speed vmZ2 of one feeding cycle C (when the wire feeding is reversed) can be used as parameters of the feeding speed v. In FIG. 4, the average feeding speed vm, the positive average feeding speed vmZ1 and the negative average feeding speed vmZ2 are illustrated for the first feeding cycle C.

[0048] For example, the time interval t1 of the first period Z1 of each feed cycle C can be measured as the actual value t1. In this case, the target value t1_soll for the first time interval t1 is used as the target value. Similarly, the time interval t2 of the second period Z2 of each feed cycle C can be measured as the actual value t2, and the target value t2_soll for the second time interval t2 can be used as the target value. The actual value f_ist of the droplet detachment frequency f may be measured. This corresponds to the sum consisting of the time interval t1 of the first period Z1 and the time interval t2 of the second period Z2 of each feed cycle C. In this case, the target value f_soll for the droplet detachment frequency f can be used as the target value. In all three cases, one or more of the above influence parameters of the feed rate v can be changed in order to adjust each target value.

[0049] For this purpose, an appropriate controller, for example a PI controller or a PID controller, can be beneficially provided in this control device 13. The controller is configured to calculate a control quantity S for the feed device 7, in particular the drive device 7a, from the respectively measured actual values, for example the actual value t1_ist of the time interval t1 of the first period Z1 (or the measured actual value t2_ist of the time interval t2 of the second period Z2), and a preset, preferably constant, target value, for example t1_soll, t2_soll or f_soll. At this time, in order to adjust the feed rate v, as shown in FIG. 3, the control device 13 appropriately operates the feed device 7 with the calculated control quantity S.

[0050] Thereby, by continuously adjusting the set parameters, such as the average wire feed speed vm and / or the positive average wire feed speed vmZ1 and / or optionally the negative average wire feed speed vmZ2, the short - circuit period t2 or the non - short - circuit period t1 can be adjusted to the desired value. Therefore, it is possible to automatically correspond to the variable influencing parameters mentioned at the beginning (for example, the variable distance X between the electrode 4a and the workpiece 10, the variable angle α between the electrode 4a and the welding wire 8 - see Figure 2 or the variable welding speed G in the direction of the weld joint 32 - see Figure 3). This improves the quality of the welding, especially during manual welding. For example, when the welding speed G is unconsciously increased by the welder, the amount of filler material in the molten pool 26 decreases, so generally the non - short - circuit period t1 is automatically extended. In this case, by the control of the present invention, for example, the average wire feed speed vm is increased and thus automatically adapted to the increased welding speed G (and vice versa).

[0051] The target value t2_soll for the short - circuit period t2, the target value t1_soll for the non - short - circuit period t1, and the target value f_soll for the droplet detachment frequency f can be regarded as known and can be stored in the control unit 13, for example, as constant values. The target values can also depend on the diameter of the welding wire 8 and / or the material of the welding wire 8 and / or the electrical welding parameters (for example, the welding current I_s or the welding voltage U_s). Therefore, corresponding target values can be automatically set depending on the actual welding parameters (which can be regarded as known due to the selected welding program). Furthermore, the target values can also depend on the joint shape (fillet joint, V - joint, etc.) of the weld joint 32 to be formed.

[0052] For example, a function for a target value can be stored in the control device 13 depending on at least one variable (for example, welding voltage I_s). At this time, the control device 13 can calculate the target value from the function. When the target value depends on a variable, the function can be stored, for example, as a characteristic curve. When the target value depends on a plurality of variables, the function can be stored, for example, as a characteristic map. Naturally, if necessary, the welder may further perform manual adjustment, for example, via the user interface 14. For example, the initially set target value can be increased or decreased by the welder in a preset (for example, percentage-based) step width.

[0053] In FIG. 4, it can be seen that the duration of each feeding cycle C and the height of the feeding speed v change automatically during control, and here in particular decrease. In the first cycle shown, the error, that is, the difference Δt1 between the actual value t1_ist and the target value t1_soll, is relatively large, while the error is reduced by adjusting the feeding speed v until the actual values t1_ist, t2_ist reach the preset target values t1_soll, t2_soll. This is illustrated in the last cycle and the cycle before it in FIG. 4. In these cycles, the error is controlled to a sufficiently small value, in particular zero.

[0054] As shown in the figure below Figure 4, in order to change the average feed rate vm or the positive average feed rate vmZ1, the feed rate v is first set to a higher positive first value v1 during the boost period tu at the start of each feed cycle C, and after the boost period tu has elapsed, it is beneficial to be reduced to a positive second value v2 < v1 that is lower than the positive first value v1. Furthermore, this has been demonstrated to be beneficial in counteracting the inertia of the welding wire 8 and the welding torch 3. In this case, the first value v1, and / or the ratio between the first value v1 and the second value v2, and / or the length of the boost period tu may depend, for example, on the error Δt1 between the actual value t1_ist and the target value t1_soll measured at each respective actual point in time or actual time step (or the error Δt2 between the measured actual value t2_ist and the target value t2_soll). As can be seen based on the illustrated cycle, the larger each difference Δt1, Δt2 is, the higher the first value v1 and / or the longer the period tu. Thus, the ratio between the first value v1 and the second value v2 may depend, for example, on the error Δt1 (or error Δt2) during control.

[0055] However, setting the boost period tu with a high feed rate v1 is only optional, and the average feed rate vm or the positive average feed rate vmZ1 can also be changed, for example, only by changing the value v2.

[0056] As described above, the present invention is not limited to the WIG welding described, and can also be used in laser welding or WIG / laser hybrid welding or plasma welding.

Claims

1. To form a molten pool (26), energy is applied by a non-consumable electrode (4a) as a heat source (4) to the region of the welding location (25) on the workpiece (10), and a welding wire (8) separate from the heat source (4) is fed into the molten pool (26). In a welding method in which the welding wire (8) is melted within the region of the molten pool (26) by the applied energy to form a welded joint (32) on the workpiece (10), the welding wire (8) is fed into the molten pool (26) in an intermittent feeding cycle (C), preferably with a reversed feeding speed (v), during the execution of the welding method, the actual value (t1_ist) of the time interval (t1) of the first period (Z1) of each feeding cycle (C) during which the welding wire (8) is not in contact with the molten pool (26) is measured, and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) of each feeding cycle (C) during which the welding wire (8) is in contact with the molten pool (26) is measured, at least one set parameter of the feeding speed (v) of the welding wire (8) is changed depending on the actual value measured during the feeding cycle (C) and a preset target value, the time interval (t1) of the first period (Z1) of each feeding cycle (C) is measured as the actual value (t1_ist), and the target value (t1_soll) for the first time interval (t1) is used as the target value, or the time interval (t2) of the second period (Z2) of each feeding cycle (C) is measured as the actual value (t2_ist), and the target value (t2_soll) for the second time interval (t2) is used as the target value, or the sum consisting of the time interval (t1) of the first period (Z1) and the time interval (t2) of the second period (Z2) of each feeding cycle (C) is measured as the actual value (f_ist), and the target value (f_soll) for the droplet detachment frequency (f) is used as the target value. A welding method characterized by this is provided.

2. The average feeding speed (vm) of the entire feeding cycle (C) and / or the positive average feeding speed (vmZ1) of the feeding cycle (C) and / or the negative average feeding speed (vmZ2) of the feeding cycle (C) are used as parameters of the feeding speed (v). The welding method according to Claim 1 is characterized by this.

3. At the start of each feed cycle (C), during a set boost period (tu), the feed rate (v) is set to a predetermined first value (v1), and after the elapse of the boost period (tu), by decreasing from the first value (v1) to a predetermined second value (v2), the average feed rate (vm) or the positive average feed rate (vmZ1) is changed. The first value (v1), and / or the ratio between the first value (v1) and the second value (v2), and / or the length of the boost period (tu) is preferably set depending on the error (Δt1, Δt2) between the measured actual values (t1_ist, t2_ist) and the preset target values (t1_soll, t2_soll). The welding method according to claim 1 or 2, characterized in that.

4. The energy is applied to the workpiece (10) via an electric arc (27) formed between the non-consumable electrode (4a) and the workpiece (10), and / or The energy is applied to the workpiece (10) by a laser beam formed by a laser optical device. The welding method according to any one of claims 1 to 3, characterized in that.

5. The actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) are measured continuously or discretely, and / or The preset target value is adjusted by changing at least one parameter of the feed rate (v). The welding method according to any one of 1 to 4, characterized in that.

6. The target value is set depending on the diameter of the welding wire (8) and / or the material of the welding wire (8) and / or the electrical welding parameters, in particular the welding current (I_s) and / or the shape of the joint of the welded joint (32). The welding method according to any one of claims 1 to 5, characterized in that.

7. Preferably, the potential (P_ist) is taken out by the welding wire (8). The actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) are obtained from the time evolution of the taken-out potential (P_ist). Measure the measured voltage (U_m) between the welding wire (8) and the workpiece (10) and / or the measured current (I_m) passing through the welding wire (8), and determine the actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) from the time progression of the measured voltage (U_m) and / or the measured current (I_m), thereby extracting the potential (P_ist). Preferably, the ground potential is formed between the welding wire (8) and the workpiece (10). The welding method according to any one of claims 1 to 6, characterized in that.

8. A welding torch (3) having a non-consumable electrode (4a) as a heat source (4) for applying energy to a welding location (25) on a workpiece (10) to form a molten pool (26), A feeding device (7) for feeding a welding wire (8) separate from the heat source (4) to the molten pool (26), wherein the welding wire (8) is melted within the region of the molten pool (26) by the energy applied from the heat source (4) to form a welded joint (32) on the workpiece (10). A feeding device (7). In a welding apparatus (1) including a control device (13) for controlling the feeding device (7). The control device (13) is configured to operate the feeding device (7) such that the welding wire (8) can be fed to the molten pool (26) in an intermittent feeding cycle (C), preferably with a reversing feeding speed (v). During the welding method performed by the welding apparatus (1), measure the actual value (t1_ist) of the time interval (t1) of the first period (Z1) of each feeding cycle (C) in which the welding wire (8) is not in contact with the molten pool (26), and / or measure the actual value (t2_ist) of the time interval (t2) of the second period (Z2) of each feeding cycle (C) in which the welding wire (8) is in contact with the molten pool (26). A measuring device (31) is provided and configured as follows. The control device (13) is configured to operate the feeding device (7) to change at least one set parameter of the feeding speed (v) of the welding wire (8) depending on the actual value measured during the feeding cycle (C) and a preset target value. The actual value (t1_ist) is the time interval (t1) of the first period (Z1) of each feed cycle (C), and the target value is the target value (t1_soll) for the first time interval (t1), or, The actual value (t2_ist) is the time interval (t2) of the second period (Z2) of each feed cycle (C), and the target value is the target value (t2_soll) for the second time interval (t2), or, The actual value (f_ist) is the sum consisting of the time interval (t1) of the first period (Z1) and the time interval (t2) of the second period (Z2) of each feed cycle (C), and the target value is the target value (f_soll) for the droplet detachment frequency (f), characterized by the welding apparatus (1).

9. The parameter of the feed rate (v) includes the average feed rate (vm) of the entire feed cycle (C), and / or the positive average feed rate (vmZ1) of the feed cycle (C), and / or the negative average feed rate (vmZ2) of the feed cycle (C), characterized by the welding apparatus (1) according to claim 8.

10. In order to change the average feed rate (vm) or the positive average feed rate (vmZ1), at the start of each feed cycle (C), the control device (13) sets the feed rate (v) to a predetermined first value (v1) during the set boost period (tu), and the feed rate (v) is configured to decrease from the first value (v1) to a predetermined second value (v2) after the elapse of the boost period (tu), The first value (v1), and / or the ratio between the first value (v1) and the second value (v2), and / or the length of the boost period (tu) are preferably set depending on the error (Δt1, Δt2) between the measured actual value (t1_ist, t2_ist) and the preset target value (t1_soll, t2_soll), characterized by the welding apparatus (1) according to claim 8 or 9.

11. The heat source (4) has a non-consumable electrode (4a) for forming an electric arc (27) between the electrode (4a) and the workpiece (10), and / or, The heat source (4) has a laser optical device for generating a laser beam, characterized by the welding apparatus (1) according to any one of claims 8 to 10.

12. The measurement device (31) is configured to continuously or discretely measure the actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2). This measurement device (31) is preferably incorporated into the control device (13), and / or, The control device (13) has a controller configured to calculate a control amount (S) for the feeding device (7) from the measured actual value and a preset target value. The welding apparatus (1) according to any one of claims 8 to 11, wherein the control device (13) is configured to operate the feeding device (7) by the calculated control amount (S) in order to adjust the target value.

13. The measurement device (31) has a potential detection device (30) configured to extract the potential (P) generated around the heat source (4) with the welding wire (8). The measurement device (31) is configured to obtain the actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) from the time change of the extracted potential (P_ist). Preferably, the potential detection device (30) has a voltmeter (29) for detecting the measurement voltage (U_m) between the welding wire (8) and the workpiece (10), and / or an ammeter (33) for detecting the measurement current (I_m) passing through the welding wire (8). The measurement device (31) is configured to obtain the actual value (t1_ist) of the time interval (t1) of the first period (Z1) and / or the actual value (t2_ist) of the time interval (t2) of the second period (Z2) from the time change of the measurement voltage (U_m) and / or the measurement current (I_m). The welding apparatus (1) according to any one of claims 8 to 12, wherein an auxiliary power source is provided, and the ground potential can be generated between the welding wire (8) and the workpiece (10) by this auxiliary power source.

14. The target value depends on the diameter of the welding wire (8) and / or the material of the welding wire (8) and / or the electrical welding parameters (I_s, U_s) and / or the shape of the joint of the welded joint (32). The welding apparatus (1) according to any one of claims 8 to 13.

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