Patent Application
20110011836
The instant invention relates to a method for plasma keyhole welding of a workpiece using at least one process gas, wherein the gas composition and/or at least one gas volume flow rate of the process gas are temporally changed, and to a corresponding device.
Welding refers to the bonding of components by material engagement using heat and/or pressure, if applicable using additional welding materials. Fusion welding methods are used, for the most part, for metals, but also in the case of the welding of glass or for thermoplastic synthetic materials. In the case of fusion welding, welding is typically carried out by means of a locally limited melt flow without using force and thus without pressure. As a rule, the bonding of the components takes place in the form of weld seams or spots.
The gas-shielded arc welding forms one group of welding methods comprising particularly advantageous characteristics, among which the plasma welding takes a special place. The plasma welding is part of the tungsten protective gas (WP) methods, in the case of which a plasma jet serves as heat source. The plasma jet is generated by means of ionization and constriction of an arc, is directed onto a workpiece and is moved along a desired weld seam course, for example. The constriction of the plasma jet to an almost cylindrical gas column (as a rule by means of a water-cooled copper nozzle, mostly with the aid of a so-called focusing gas) results in a higher energy concentration than in the case of conventional welding methods, such as the TIG welding, for example. Up to three gases or gas mixtures can thereby be supplied via concentric nozzles in a plasma burner, which concentrically surrounds the electrode, among them the plasma gas, the focusing gas for constricting the plasma jet and the protective gas. In the case of the common methods, the plasma jet and the focusing gas are enveloped by protective gas. Among others, the use of protective gas serves the purpose of protecting the melt from oxidation during the welding process. The plasma welding is a welding method, in the case of which a constricted arc is used. In the case of plasma welding by means of a transferred arc, the arc burns between the electrode, which does not melt, and the workpiece. By constricting the arc, higher energy densities are reached than in the case of common arc welding comprising a non-melting electrode, the so-called TIG welding.
The plasma keyhole welding represents an alternative of the plasma welding. As a high performance welding method, it allows for the processing of greater sheet thicknesses with small thermal distortion and high welding speeds and is currently mainly used for the joining of chromium-nickel steels by means of welding technology. Today, this technology is furthermore resorted to when particular demands are made on the quality of the weld seam with reference to through-welding, weld shape and weld appearance. As a rule, it is used up to a sheet thickness of 8 to 10 mm. The main areas of application lie in the chemical plant construction, the aerospace industry as well as in the tank and pipeline construction.
In the case of plasma keyhole welding, the plasma jet passes through the entire workpiece thickness at the onset of the welding process. The melting bath, which is created by the melting of the workpieces, is thereby pushed to the side by the plasma jet. The surface tension of the melt prevents a falling through the keyhole. Instead, the melt flows together again downstream from the weld eye, which forms, and solidifies to the weld seam.
In the case of plasma keyhole welding, likewise as in the case of plasma welding, up to three gas flows are used as process gas. The plasma gas is located in the interior. Due to the high energy density in the interior, the plasma gas forms the plasma jet. As a rule, the plasma gas is surrounded by a protective gas, the main object of which is to protect plasma jet and processing location from undesired impacts from the environment. In many cases, a so-called focusing gas is furthermore also used, which supports the constriction and orientation of the plasma jet and which is normally guided between plasma and protective gas.
The process-reliable embodiment of the keyhole is an indispensable requirement for the use of the plasma keyhole welding. Basic requirement for this are an accurate weld edge preparation, which is connected with high requirement of time, and a corresponding positioning of the components as well as the accurate maintaining of the weld parameters. In response to deviations from these basic conditions, e.g. by variable clearances and offsets as well as switches in geometry, which cause a changeable heat conduction into the component, can lead to the insufficient full permeation welding, the formation of spillings, the appearance of undercuts or to the sagging of the weld pool. Exactly in the case of the most commonly welded unalloyed and low-alloyed steels (such as construction steel), these process instabilities appear to in increased extent also due to the high variations of the chemical composition (alloy) as well as due to a low surface tension and viscosity.
The use of the plasma keyhole welding is thus currently possible for the component preparation only with cost and time-intensive efforts. The maximally realizable welding speed further reduces considerably with an increasing sheet thickness; especially the stability of the welding process furthermore also decreases. The difficulty of a stable keyhole embodiment, which dominates in particular in the case of plasma keyhole welding of construction steel, thus currently limits the industrial practicability of the method in this field to a considerable extent.
Different approaches are known to improve a secure and stable embodiment of the keyhole under praxis-relevant conditions, such as, e.g., long arcing times, different sheet surfaces, non-optimal ground connection, fluctuations in the alloy composition and the like.
It is known to pulse the plasma gas in response to the generation of plasma arcs. For instance, EP 257766 A2 discloses a method, in the case of which the plasma gas flow and/or the welding current is modulated to such a high degree that an intermitting perforation of the material or spot welding can be attained.
Optical, pneumatic and/or electric parameters can be monitored during the welding process for the constant control of the keyhole embodiment. For instance, the brightness of the plasma jet passing through, the pressure resulting from its kinetic energy and/or the electric conductivity of its portion escaping on the rear side of the workpiece (so-called permeation current) can be used as control variable for the full permeation welding. The keyhole embodiment is then held so as to be constant over a variation of the welding current. For this, the welding current is mostly adjusted to a basic level and can be raised to an increased value (pulse level), if applicable, so as to supply more energy to the component. However, due to the fact that the thermal load capacity of the plasma gas nozzle limits the maximal welding current, the capability of the plasma burner cannot be used completely in the base current phase, because a “reserve” for the pulse level is to be provided in each case.
To increase the maximal welding speed and/or the maximally weldable sheet thickness, EP 689896 A1 discloses a method, in the case of which the volume flow rate of the plasma gas and thus its energy density is changed periodically at a constant frequency via the mentioned welding process.
JP 08039259 A also contains a method for periodically varying the plasma gas in response to plasma and plasma keyhole welding in pulsed operation.
U.S. Pat. No. 3,484,575 A discloses a periodic change of the composition of the protective gas in response to welding by changing at least one volume flow rate.
DE 102007017223 A1 and DE 102007017224 A1 disclose methods for plasma keyhole welding, wherein a gas mixture is in each case used as plasma gas and/or as protective gas. At least one gas composition or at least one gas volume flow rate, respectively, are temporally changed several times during the welding process, whereby a temporally changing back pressure is exerted onto the melt and said melt is thus oscillated. Through this, the process stability increases in response to the joining of the melt downstream from the keyhole and the kinematics of the keyhole formation is changed advantageously. The energy density of the plasma jet can furthermore be varied by means of the temporally changeable composition or the temporally changeable gas volume flow rate of the focusing gas, respectively.
The instant invention is thus based on the object of providing a method and a device for plasma keyhole welding, by means of which the process stability and handling, in particular the stability of the keyhole embodiment is improved and/or the maximally realizable welding speed is increased.
This object is solved by means of the features of the independent patent claims. Advantageous embodiments result from the respective dependent claims and from the following description.
With reference to the method, the posed object is solved in that, in a method for plasma keyhole welding of a workpiece using at least one process gas, wherein the gas composition and/or at least one gas volume flow rate of the process gas are changed temporally, the gas volume flow rate and/or the gas composition of at least one process gas are temporally changed during a welding process as a function of at least one basic condition of the welding process according to the invention.
In the context of this application, “process gas” (also referred to as “welding gas”) refers to one of the gases used in response to the plasma keyhole welding, such as a plasma gas, a focusing gas and/or a protective gas or forming gas, for example.
A “temporal change” of the gas composition and/or of the gas volume flow rate comprises in particular a gradual, continuous and/or and increase, decrease and/or modulation, which can be described by means of a mathematical function, in particular also a periodic change of a component of a gas composition. The frequency, the phase, the amplitude and/or the base line of a periodically changing gas composition and/or of a periodically changing gas volume flow rate can be varied due to changed basic conditions.
“Workpiece” refers to one or a plurality of elements, in particular metallic elements, which are processed by means of plasma keyhole welding.
A corresponding change can take place in the context of a control cycle or can be input by a user, if applicable on the basis of read indicated values or on the basis of a corresponding signal. The basic conditions can hereby also relate to a plurality of or to all used process gases, that is, they can cause a corresponding temporal changes, but provision can also be made, however, for certain known or measured basic conditions to selective act on individual process gases. It is emphasized in this context that the temporal change during the welding process can be carried out in particular by means of an automatic regulation. The person of skill in the art will clearly define these changes of simple set-up or optimizing processes, respectively, at the onset of a welding process, in the case of which a composition and/or a volume flow rate of a process gas can also be changed and, as a rule, can be adapted once to the weld conditions and to the material.
In the event that the melt is oscillated by adaptation to basic conditions, for example by changing a (periodically modulated) volume flow rate, the process stability increases in a particularly advantageous manner in response to the joining of the melt downstream from the keyhole. By means of the method according to the invention, the kinematics of the keyhole formation is changed (adaptively) in adaptation to the currently available conditions. The maximally realizable welding speed can be increased through this, without significantly increasing the energy input per unit length, that is, the application of energy into the workpiece based on the length of the weld seam, thus causing a smaller distortion of the material, which is to be welded.
Advantageously, the basic conditions comprise characteristics of the workpiece as well as parameters of the welding process, in particular the change thereof. The characteristics of the workpiece can be geometric and/or (physico-)chemical characteristics. Among others, the geometric characteristics include the material thickness, the clearances, deviations in the weld seam preparation and the offset between elements of the workpiece. The chemical characteristics can be alloy or material characteristics (e.g. phases of steel), which impact the welding process.
Advantageously, the parameters of the welding process and/or the characteristics of the workpiece are determined by means of optical, pneumatic and/or electric characteristics of the plasma jet (brightness/pressure or conductivity, respectively). However, it is also possible to determine the characteristics of the focusing gas or of the protective gas or to determine the behavior of the welding process via other parameters, such as, for example, welding stress or characteristics of the melt. In particular in the event that characteristics of the plasma jet change, a reaction can the take place by means of a suitable adaptation of a gas volume flow rate. For instance, the quality of a plasma jet, for example, can be assessed by measuring the permeation current between a workpiece and a forming gas rail, which is affixed therebelow. The volume flow rate of a gas can then be adapted as a function of the measured values. If, for example, the width of a weld gap increases in a predictable or unpredictable manner, a larger portion of the plasma jet passes through the weld gap. The energy quantity available for the welding process decreases, the permeation current increases. In the event that a change is made to a gas volume flow rate on the basis of the detected change of the permeation current, the energy density of the plasma jet can be increased, so that the energy introduced into the workpiece increases. In response to a change of an alloy composition, the keyhole can widen or constrict due to an improved or worse fusibility of the material. Through this, a larger or smaller portion of the plasma jet passes through the keyhole accordingly. The permeation current is increased or decreased. To constrict a keyhole, which is too large, or to widen a keyhole, which is too small, a change of a gas volume flow rate can then be carried out on the basis of the permeation current, whereby the energy density of the plasma jet can be decreased or increased.
A change of the composition of a process gas is possible by means of an increase or decrease of the absolute or relative shares of individual gases of a mixture. For example, a first gas comprising a first, constant volume flow rate and a second gas comprising a second, pulsing volume flow rate can also be provided, whereby the composition of the mixed process gas, which results therefrom, changes accordingly in a pulsing manner. With this, allowances can be made, for example, for changing material compositions. For example, variable mixtures of inert with active process gases can be used, which make it possible to positively impact the welding process in terms of an improvement of the plasma jet quality, the melting deposition rate, the seam surface, the avoidance or limitation of a formation of spillings, of disadvantageous undercut formations or high gas contents in the weld metal deposit. In particular by means of an adaptive change of the composition of the plasma gas, its heat conductivity and its enthalpy can be impacted in consideration of the basic conditions.
Advantageously, the basic conditions comprise characteristics of the workpiece as well as parameters of the welding process, in particular the change thereof. The characteristics of the workpiece can be geometric and/or (physico-)chemical characteristics. Among others, the geometric characteristic include the material thickness, the clearances, deviations in the weld seam preparation and the offset between elements of the workpiece. The chemical characteristics can be alloy or material characteristics (e.g. phases of steel), which impact the welding process. A differentiation can be made between predictable (known) and unpredictable (unknown) changes, which can relate to the geometric as well as to the chemical characteristics. For example, a known, continuous increase of the thickness of the workpiece or of a known change of the material composition by adapting the composition of a gas can cause a particularly stable welding process.
Advantageously, the at least one process gas, the gas volume flow rate of which is temporally changed, comprises a plasma gas, a focusing gas and/or a protective gas. By means of a corresponding modulation of the plasma gas, the energy density of the plasma jet, for example, and thus the energy introduced into the workpiece, can be impacted. The change of the volume flow rate of the focusing gas causes a higher or weaker focusing of the plasma jet and thus also a modulation of the energy density. By impacting the volume flow rate of the protective gas, the protective effect against oxidation can be adapted, provided that this is required, for example due to a larger melting volume or a change of the material composition, and/or the stability of the welding process can be improved. All of the process gasses interact in response to the adjustment of the back pressure to the melt. Said melt can be oscillated by this, for example.
Advantageously, the parameters of the welding process and/or the characteristics of the workpiece are determined by means of optical, pneumatic and/or electric characteristics of the plasma jet. In the event that the characteristics of the plasma jet change, in particular due to unpredictable changes of characteristics of the workpiece, which is to be welded, a reaction can then take place by means of a suitable adaptation of a gas composition. For instance, the quality of a plasma jet, for example, can be assessed by measuring the permeation current between a workpiece and a forming gas rail, which is affixed therebelow. The composition of a gas can then be adapted as a function of the measured values. If, for example, the width of a weld gap increases in a predictable or unpredictable manner, a larger portion of the plasma jet passes through the weld gap. The energy quantity available for the welding process decreases, the permeation current increases. In the event that a change is made to a gas volume flow rate on the basis of the detected change of the permeation current, the energy density of the plasma jet can be increased, so that energy introduced into the workpiece increases. In response to a change of an alloy composition, the keyhole can widen or constrict due to an improved or worse fusibility of the material. Through this, a larger or smaller portion of the plasma jet passes through the keyhole. The permeation current increases or decreases. To constrict a keyhole, which is too large, or to widen a keyhole, which is too small, a change of a gas volume flow rate can then be carried out on the basis of the permeation current, whereby the energy density of the plasma jet can be decreased or increased.
Advantageously, the at least one process gas, the composition of which is temporally changed, comprises a plasma gas, a focusing gas and/or a protective gas. By means of a corresponding modulation of the plasma gas, the energy density of the plasma jet, for example, and thus the energy introduced into the workpiece, can be impacted. The change of the composition of the focusing gas causes a higher or lower focusing of the plasma jet and thus also a modulation of the energy density. By impacting the composition of the protective gas, the protective effect against oxidation can be adapted, provided that this is required, for example due to a larger melt volume or a change of the material composition. All of the process gases interact in response to the adjustment of the back pressure to the melt. Said melt can be oscillated by this, for example.
According to an advantageous embodiment of the invention, at least one of the process gases, in particular the plasma gas, the focusing gas and/or the protective gas encompasses at least one gas from the group of argon, helium, nitrogen, carbon dioxide, oxygen and hydrogen. Gases or gas mixtures, which contain at least one gas from the mentioned group, are accordingly preferably used as plasma gas and/or as focusing gas and/or as protective gas. The determination of the suitable gas or of the suitable gas mixture, respectively, takes place as a function of the weld object, in particular in consideration of the base material, which is to be welded, and possible filler materials, as mentioned above, in adaptively changing compositions.
Advantageously, the clean gases as well as two, three and multi-component mixtures are used. A particularly selective adaptation to the weld object is effected through this.
In many cases, doped gas mixtures can also prove to be particularly advantageous, wherein doped gas mixtures encompass dopings with active gases in the vpm range. Preferably, the doping takes place in the range of less than 2.5, in particular 1.0 volume percent, for the most part less than 0.1 volume percent.
Advantageously, active gases, such as, e.g., oxygen, carbon dioxide, nitrogen monoxide, nitrous oxide (dinitrogen monoxide) or nitrogen can be used.
According to a particularly advantageous embodiment of the invention, the volume flow rate and the composition of at least one process gas, in particular of the plasma gas, the focusing gas and/or the protective gas can be temporally changed. In the event that the melt is oscillated by adaptation to basic conditions, for example by changing a volume flow rate in a pulsing manner, the process stability increases in a particularly advantageous manner when the melt joins downstream from the keyhole. By means of the method according to the invention, the kinematics of the keyhole formation is changed (adaptively) in adaptation to the currently available conditions. In the event that a gas volume flow rate is provided in a pulsing manner, a pulsing of the plasma jet can be effected. Through this, the maximally realizable welding speed can be increased without significantly increasing the energy input per unit length, that is, the application of energy into the workpiece based on the length of the weld seam, thus causing a smaller distortion of the material, which is to be welded. A change of the composition of a process gas is possible by means of an increase or decrease of the absolute or relative shares of individual gases of a mixture. For example, a first gas comprising a first, constant volume flow rate and a second gas comprising a second, pulsing volume flow rate can also be provided, whereby the composition of the mixed process gas, which results therefrom, changes accordingly in a pulsing manner. With this, allowances can be made, for example, for changing material compositions. For example, variable mixtures of inert with active process gases can be used, which make it possible to positively impact the welding process in terms of an improvement of the plasma jet quality, the melting deposition rate, the seam surface, the avoidance or limitation of a formation or of spillings, of disadvantageous undercut formation of high gas contents in the weld metal. In particular by means of an adaptive change of the composition of the plasma gas, its heat conductivity and its enthalpy can be impacted in consideration of the basic conditions.
It is pointed out here that the simplest possibility for changing a gas volume flow rate is to either change the flow or to turn on or turn off, respectively, a second gas flow comprising the same gas composition. Accordingly, the gas composition can be changed by mixing different gases, which are provided in volume flow rates, which are temporally changeable to one another. A change of a gas composition can be accompanies by a volume flow rate change when a different gas is turned on, for example.
Advantageously, the welding current is furthermore temporally changed, in particular it is welded with pulsed current. A welding with a direct or alternating current is also possible. By means of a corresponding change, in particular by adaptation to the mentioned basic conditions, an additionally improved adaptation to the weld object can be effected by impacting the application of energy.
A further advantageous embodiment of the invention hereby provides for a welding to be carried out by means of pulsing welding current (pulsed current), wherein each period is comprised of a pulsed current phase (high current phase) and a base current phase (low current phase). A welding current, which is provided in a pulsed manner, increases the process reliability in addition to the mentioned measures.
According to an advantageous development, the mentioned temporal changes of the gas volume flow rate, of the composition of at least one process gas and/or of the welding current are carried out so as to be tuned to one another. Preferably, a temporal change of the gas composition, of a gas volume flow rate of at least one process gas and/or of the welding current takes place as a function of at least one further temporal change of a gas composition, of a volume flow rate and/or of a welding current.
It is to be insinuated that a change “as a function of at least one further temporal change” can include a change, which is in-phase, phase-shifted, rectified or directed oppositely, provided that this is advantageous.
In the case of welding by means of pulsing welding current (pulsed current), the plasma gas volume flow rate, the focusing gas volume flow rate and/or the protective gas volume flow rate, for instance, can be temporally changed synchronously or phase-shifted to the course of the pulsed current, whereby an adaptation to the respective energy, which is introduced into the material, can take place. In addition to the volume flow rate change, a corresponding composition change can also take place. And, vice versa, in addition to a composition change, a corresponding volume flow rate change can also take place.
Provision can further be made, for example, for the focusing gas to be changed synchronously to at least a further provided process gas, in particular synchronously to the plasma gas (the gas volume flow rate on its part is impacted by basic conditions). This serves, in particular, to prevent turbulences and possible disadvantageous mixing between plasma gas and focusing gas. By means of a corresponding change, the energy density of the plasma jet can be varied in a particularly advantageous manner, in that its focusing is changed adaptively.
In an analogous manner, the gas volume flow rate of the protective gas, for example, can be changed temporally as a function of the gas volume flow rate of the plasma gas and/or of the focusing gas. In addition to the mentioned prevention of turbulences, the protective gas can be provided so as to be adapted to the remaining volume flow rates by changing the volume flow rate thereof.
The change of the composition can take place in an advantageous embodiment synchronously to the change of the gas volume flow rate. In other cases, however, it can also be advantageous to change gas volume flow rate and compositions in a phase-shifted manner to one another. It is also possible to pulse gas volume flow rate and composition comprising different frequencies.
Advantageously, the temporal change of the gas composition, of a volume flow rate of at least one process gas and/or of the welding current takes place periodically at a frequency in the range of between 1 and 200 Hz, in particular between 12 and 200 Hz, in particular between 15 and 100 Hz, preferably between 20 and 80 Hz. The temporal change (according to the invention) as a function of a basic condition then takes place in the form of a change of this frequency (or also of the amplitude, of the phase or of the base line). The advantages of the invention also present themselves in a distinctive manner up to frequencies of 200 Hz, particularly distinctive up to 100 Hz and in particular up to 80 Hz. It turned out in particular for the plasma gas that the plasma contracts almost continuously due to its inertia in the case of frequencies, which lie above the afore-mentioned lower limits. The contraction leads to an increase of the energy density and, as a result, to an increase of the sheet thickness, which can be welded, or to an increase of the maximum welding speed, without significantly increasing the energy input per unit length.
In an advantageous development, the modulation comprising the afore-mentioned (low) frequencies is superimposed with a further, high-frequency pulse comprising a frequency of up to 10000 Hz, preferably of up to 80000 Hz. This can either be a pure volume pulsing, but provision can also be made for a corresponding pulsing of the composition or a combined pulsing of volumes and composition. Advantageously, however, only a high-frequency pulsing of the gas volume flow rate takes place in addition to the low-frequency pulsing. Plasma gas and/or focusing gas and/or protective gas can be affected by the additional high-frequency pulsing. This additional high-frequency pulsing can take place during the entire period of the (low-frequency) pulsing or only during a certain time period within the period. The frequencies for the high-frequency pulsing of the gas volume flow rate and/or of the gas composition lie in the range of from 100 to 10000 Hz, preferably in the range of from 250 to 8000 Hz and particularly preferably in the range of from 500 to 5000 Hz. For example, a low-frequency gas volume flow rate of the plasma and/or of the focusing gas can be superimposed in a particularly advantageous manner on a low-frequency gas volume flow rate of the plasma and/or of the focusing gas in the high phase and/or in the low phase. A corresponding superimposition can advantageously also take place so as to be adapted to changing basic welding conditions.
Advantageously, the temporal change of gas volume flow rate, of a composition of at least one process gas and/or of the welding current is at least partly illustrated by means of a rectangle profile. In a particularly advantageous manner, the temporal change runs according to a modified rectangle profile, which encompasses slanted shoulders. Another advantageous embodiment of the invention provides for the temporal change of the volume flow rate and/or of the composition to be illustrated at least partly by means of a triangle profile or a sinusoidal profile.
A device according to the invention for plasma keyhole welding, which encompasses an electrode, means for supplying the electrode with welding current, at least one nozzle and gas provision means for providing at least one process gas with a gas volume flow rate and a gas composition, wherein a plasma jet can be generated by means of the electrode and the at least one process gas and wherein at least one gas volume flow rate and/or at least one gas composition can be temporally changed, characterized by means for changing a gas volume flow rate and/or a gas composition of at least one process gas during a welding process as a function of at least one basic condition of the welding process.
The device according to the invention is suitable for carrying out the method according to the invention in a particular manner. The means for changing the gas volume flow rate can thereby in particular be magnetic valves or piezoelectric valves or corresponding pumps or mixers, which operate in a pulsed manner.
The welding process can be optimized in a particularly advantageous manner in an object-specific manner by suitably selecting the combination possibilities of the embodiments according to the invention.
Advantageously, a corresponding device further encompasses means for determining basic conditions and/or basic condition changes of the welding process and/or means for regulating at least one gas composition on the basis of such basic conditions and/or basic condition changes. Advantageously, a corresponding device further encompasses means for determining basic conditions and/or basic condition changes of the welding process and/or means for regulating at least one gas volume flow rate on the basis of such basic conditions and/or basic condition changes. Equipment, which is already present in the device, for example those for optically, pneumatically and/or electrically assessing the plasma jet, can serve as means for determining basic conditions. In particular the means for regulating can thereby be a part of a superordinate regulating device or of a corresponding arithmetic unit.
With reference to further features, embodiments and advantages of the device according to the invention, reference is made expressly to the explanations with reference to the method according to the invention.
The invention as well as further embodiments of the invention will be defined in more detail below by means of the exemplary embodiments illustrated in the figures. In detail:
A device for plasma keyhole welding according to the state of the art is illustrated in
A plasma jet 7 forms under the impact of the stress on the electrode 2 in the presence of the plasma gas 5. It is illustrated in the figure, how the plasma jet 7 permeates through the workpiece 8 through a keyhole 9 from an inlet 8′ in the direction of an outlet side 8″. Provision is made on the outlet side 8″ of the plasma jet 7 for an electric conductor 10, which is not defined in detail, which can be embodied as part of a forming gas rail. Ducts 11, 11′, which are ducts for water cooling and/or for ducts by means of which a protective gas or a corresponding further process gas can be provided, are embodied in the electric conductor 10 and/or in the corresponding forming gas rail. The electric conductor 10 is connected to the positive pole of the welding current source 12 via lines 14 and 16, the workpiece 8 via lines 14 and 15.
A measuring or evaluation unit 19, symbolized herein as a computer, which measures the currents I1 and I2 between the electrode 2 and the workpiece 8 or the conductor 10, respectively, via measuring lines 17 and 18, is furthermore illustrated in
In the partial
It is shown in
A gas component A is continuously pulsed with a sinusoidal course in
In a similar manner,
It is to be insinuated that, even though frequencies, which are not superimposed, are illustrated in
In the partial
It is shown in
In a similar manner,
It is to be insinuated that, even though
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 027 784.6 | Jul 2009 | DE | national |
| 10 2009 027 785.4 | Jul 2009 | DE | national |
| 09 013 534.4 | Oct 2009 | EP | regional |
