DE2265065A1 - Arc welding using a consumable electrode - with pulsating stream of carbon dioxide directed onto molten end of the electrode - Google Patents

Abstract

Process fo rarc welding with a consumable electrode, esp. protective gas welding using carbon dioxide gas, the novelty being that the consumable end of the electrode, esp. protective gas welding using carbon dioxide gas, the novelty being that the consumable end of the electrode is subjected to a gas stream with a predetermined frequency of pulsation. The pulsating gas stream pref. has a frequency of 1-200 Hz, esp. 1-50 Hz, and forms a ring round the electrode, the stream pref. being surrounded by a continuously flowing gas curtain. Allows the controlled, predetermined transfer of drops of molten metal from the end of the electrode which is largely independent of the influence of gravity; smaller drops are obtd., reducing the risk of short circuits, and increased penetration results.

Description

MESSER GRIESHEIM GMBH MG 688a

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Ii: ^ I.; i2 ni '^ lxiS 10/17/1975

Password: Pulspneuraarc II
Inventor: Dr. Teske, Hannappel

Process for arc welding with a consumable electrode, in particular for inert gas welding under CO ₂

The present invention relates to a method for arc welding with a consumable electrode, in particular for inert gas welding under CO ₂ When welding with a consumable electrode, the transition of the weld metal from the electrode to the workpiece depends on the welding process used, such as MIG and MAG arc welding, which also includes submerged arc welding.

In immersion arc welding (DIP transfer) with consumable As is known (US Pat. No. 2,886,696), the electrode end becomes the electrode under protective gas (in particular carbon dioxide) periodically immersed in the weld pool. This creates periodic short circuits, so that inevitably a pulsation of the welding current forms. In this known method, the arc is extinguished periodically and the metal transition takes place only when the electrode and workpiece are in contact. This creates a small, easy-to-manage weld pool with good gap-bridging properties. However, if this method is used, for example with sheet metal thicknesses of over 2 to 3 mm, the performance is achieved

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Increase the current strength and thus the amount of wire fed in, which at the same time reduces the short-circuit frequency, i.e. if the number of short circuits per second is increased, the seam appearance deteriorates. aside from that the arc becomes unstable due to the increase in the amperage and the use of carbon dioxide as a protective gas and the welding material is partially spattered.

If, on the other hand, an inert gas or a mixed gas, which for the most part consists of an inert gas such as If argon or helium is used, the so-called spray arc is achieved with increased current and voltage values. which is characterized by the fact that many droplets of material (up to about 500 / sec) are short-circuit-free like spray rain from the wire electrode to the workpiece. The arc with spray transition is stable and connected the small size of the droplets has the advantage that the droplets easily hit a horizontal fillet weld or directed towards an overhead seam. the Concentration of the energy in the central area of the arc and the kinetic energy of those impacting the weld pool Metal droplets cause deep penetration, which, however, is often undesirable for out-of-position welding is because the overheated weld metal formed in large quantities by axial spraying at high current densities is too liquid is; consequently, the management of the weld pool is difficult,

Because of the relatively deep penetration, the application of arc with spray transition to the weld is thicker Cross-sections limited. In the case of thin parts, the deep penetration may lead to holes, so that the weld Such parts using the axial spray transition is difficult, if not impossible. With pulse arc welding it has become possible to take advantage of the benefits

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of the spray arc can also be used with thin metal sheets.

When pulsed arc welding (German patent specification 1 149 472) is used for a short-circuit-free drop transfer required high current strength of the electrode not continuously but only at short intervals (current pulse) fed.

On the problems of material transfer in short arc welding, MIG-VMAG welding, as well as pulsed arc welding will also be in the articles

- "The material transition in MIG and MAG welding" by Dr.-Ing. W Ruckdeschel, Lohhof Reprint from DVS reports, Volume 18 'Inert gas welding ¹ Deutscher Verlag für Schweißtechnik GmbH, Düsseldorf

- "Impulse arc welding" by Karl Schöbel, Frankfurt Special print 13/68 from Elektrotechnische Zeitschrift ETZ-B Volume 2OC1968) Issue 5, VDE-Verlag GmbH, Berlin

- "Contribution to knowledge of the processes involved in short-arc welding von S ^ hI "Dr.-Ing. Folkhard and Dipl.Ing. H. Keller

Special print from the specialist book series' Schweißtechnik ¹ , Volume 40 Deutscher Verlag für Schweißtechnik (DVS) GmbH, Düsseldorf

received.

However, there is a change in the known welding processes of the weld metal transition, whether controlled as with pulsed arc welding or uncontrolled as with spray arc welding can essentially only be achieved by measures relating to the supply of electrical energy, whereby however, the structure of the current sources due to the

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Lichen electrical components such as chokes, pulse power sources and the like may become considerably complicated and expensive.

In addition, it has not yet been possible to control the weld metal transition using CO2 as a shielding gas in the way that pulsed arc welding can achieve, for example, when using an inert gas (argon) or a predominantly inert gas mixed gas. One possible explanation for this is that the contact surfaces of the CO ₂ "arc are smaller than those of the argon arc. This increases the energy concentration at these points. Under argon, the drop is enveloped by the arc, so to speak, and thus heated more evenly - the weld pool is heated over a large area at the same time in contrast to carbon dioxide. Due to the high concentration of energy with CO ₂ , the metal on the underside of the droplet evaporates.

The object of the present invention is to create a welding method in which, in particular when using from C0 ~ as protective gas, a controlled, predetermined droplet transfer can be achieved, which is influenced by gravity is largely independent.

The invention consists in that the melting end the electrode is acted upon by a gas flow pulsating at a predetermined frequency.

The pulsating gas flow advantageously makes it possible to control the weld metal transition without

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Changing the set current and voltage values. For example, when welding with CO ₂ as the shielding gas and with current and voltage values / with red tones, a short circuit usually takes place (values are therefore below the critical range) Workpiece is thrown. The drop does not migrate up to the electrode, as film recordings have shown. Through the pulsating gas flow it is achieved that even with CO ₃ as protective gas, a controlled and predetermined drop transfer is possible, controlled by the frequency of the pulsating gas flow.

Furthermore, the pulsating gas flow makes it advantageous possible to use a weld metal course, in which due to the set Current and voltage values have already detached a certain number of drops from the electrode per unit of time will change. For example, Kn has shown that with the parameters: wire diameter 1 mm, voltage 38 V, current 220 Λ, 13 drops were detached per second.

By means of a pulsating current with a pulse frequency of 21 Hz, with a ratio of pulse duration to pulse pause of 1: 1 and an overpressure of the gas of about 1.5 bar the drop transfer was increased from 13 / sec to 21 / sec. the The droplet transition frequency corresponds approximately to the gas pulse frequency.

By increasing the drop frequency and the associated By reducing the size of the droplets, it is now advantageously possible to carry out a curvature in which the penetration occurs is greater than when welding without gas flow. We also refer to the diagram illustrated in FIG.

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In addition, especially when sweating overhead, exerted a supporting effect on the weld pool by the pulsating gas flow provided according to the invention.

According to a further proposal of the invention, the gas pulses have a frequency of 1 to 200 Hz., Preferably one Frequency between 1 and 50 Hz.

In an advantageous further development it is proposed according to the invention, that the pulsating gas flow acts on the melting end of the electrode in a ring shape. Under becomes annular understood here that the pulsating gas flow is supplied via a nozzle surrounding the electrode which, as an outlet opening, has an annular gap or a plurality of openings which are provided around the electrode.

This advantageously ensures that the gas pulse is applied uniformly from all sides to the melting electrode end acts. Furthermore, it is thereby advantageously achieved that the arc on its outer jacket by the gas pulses is cooled so that a contraction of the arc occurs. This advantageously results in a higher Energy conversion in the arc possible, which in turn results in an increase in the deposition rate.

Furthermore, according to a further proposal of the invention, the pulsating gas flow is from a continuously flowing one Surrounded by gas jacket. In this way, it is advantageous to influence the arc, the electrode and the weld pool as well as the pulsating gas flow through the ambient air prevented.

According to the invention, the pulsating gas stream preferably consists of carbon dioxide. However, it is also possible instead of carbon dioxide like another protective gas

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for example, He, Ar, N _{2 /} Ne or mixtures thereof to be used. The gas jacket surrounding the pulsating gas flow can also consist of one or more of the above-mentioned types of gas.

According to the invention it is further proposed that the pulsating gas flow and / or the gas jacket have a certain Percentage (approximately between 1 and 15%) of oxygen. The surface tension is created by the oxygen in the gas of the drop that forms and thereby facilitates the detachment of the drop. It goes without saying Alloying elements, e.g. rare earths, are also possible in the electrode in a manner known per se provide through which the melting character (detachment of the drop and the like) is improved.

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The invention is illustrated in the following description of exemplary embodiments explained with reference to the drawings:

Illustrated in the drawings:

Fig. 1 shows a device for carrying out the inventive device Procedure;

FIG. 2 shows an enlarged illustration of the burner shown schematically in FIG. 1; FIG.

3 shows the gas pulse device according to FIG. 1 in an enlarged illustration;

4 shows a diagram of the drop frequency as a function of gas pulse frequency and gas volume.

In Fig. 1, the device for carrying out the invention is Method denoted by 10. The device 10 has a schematically illustrated burner device 11, a power source 12 and a gas supply device 13.

The burner device 11 consists essentially of one Torch body 14, a consumable electrode 15 and

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a wire feed unit connected to the electrode 15 16, the drive rollers 17 and a motor 18 having.

The power source 12 consists of a transformer 19, a transducer 20 connected downstream of the transformer 19 and connected to a rectifier 21, as well as a control device 22 with a thyristor 23 and a pulse device 24. The output lines 25 and 26 of the rectifier 21 are connected to the electrode 15 or a workpiece 27. Furthermore, a control circuit is in the current source 12 28 is provided which has a rectifier 29, a thyristor 3 0 and a pulse generator 31 and which is connected to the motor 18 via lines 32 to supply the same.

The device 10 has a gas nozzle 33 which is equipped with a, a pulsating gas flow generating gas pulse device 34 is in connection (line 65). The gas nozzle 33 also has an outlet channel which is directed towards the melting end 36 of the electrode 15. The gas pulse device 34 is connected via a line 37 to a gas supply device 38 - in the exemplary embodiment a bundle of gas cylinders.

Due to the gas flow flowing out of the gas nozzle 33 in a pulsating manner, the drop that forms at the end 36 of the electrode 15 becomes 39 detached and thrown onto the workpiece 27.

In Fig. 2, the burner 40 is shown in an enlarged view, in which the gas nozzle surrounds the electrode 15 Ring nozzle 41 is.

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The burner 40 consists essentially of an electrode guide tube 42, which can be connected to the power line designated by 25 in FIG. 1, a pipe 42 surrounding it and on the same spanned inner part 43, an outer part 44 that encompasses the inner part, which from a two nested sleeves 45 and 46 formed jacket is enclosed. Inner part 4 3 and outer part 44 are at its part facing the melting electrode end 36, it is conically tapered. Furthermore, the inner part 43 on the opposite cylindrical area on the conical part on an external thread 47, which with a Internal thread 4 8 in the outer part 44 is in connection. By rotating the inner part 43 and outer part 44, a more or less large annular gap 49, which over the annular channel provided between the inner and outer parts 43, 4 4 50 and the bores 51, 52 with the line 65 (Fig. 1) is connected for the pulsating gas flow. This configuration advantageously ensures that the pulsating gas flow is uniformly applied to the electrode end 36 acts. The angle 53 is advantageously approximately 5 ° to 75 °, preferably approximately 10 to 30 °. In the embodiment according to 2, an angle 53 of 15 ° has proven to be advantageous exposed.

The pulsating gas flow is surrounded by a second gas flow For this purpose, an annular channel 54 is provided in the burner according to FIG. 2, which through corresponding recesses in the sleeve 45 and 46 is formed. The annular channel 54, which is connected to the interior 56 of the burner via bores 55, is connected to the gas supply device (FIG. 1) via a line 57.

The components 42, 43 and 44 and 45 and 46 are against each other fixed in a common torch holder 59.

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In FIG. 3 that is illustrated schematically in FIG. 1 Gas pulse device 34 is shown, which in the exemplary embodiment has a piston 61 moved back and forth in the cylinder 60 which is connected to an electric motor 64 via the rod 62 and the eccentric wheel 63.

The cylinder 60 is on the one hand with the gas supply device 38 via line 37 (Fig. 1) and on the other hand via the output line 65, in which a check valve 66 is arranged, with the gas nozzle 33 or 41 in connection. By changing the speed of the motor 64 is the Adjustable gas pulse frequency. The pulse intensity can be adjusted by changing the pre-pressure in line 37.

A diagram is illustrated in FIG. 4.

On the left ordinate 70 is the drop frequency in Hz, on the right ordinate 71 the gas quantity of the pulsating gas flow in l / min and on the abscissa 72 the gas pulse frequency plotted in Hz.

The curve 73 in the diagram illustrates the drop frequency as a function of the gas pulse frequency; the curve 74 the amount of gas depends on the gas pulse frequency.

The diagram shows that without gas pulses (frequency '- O) there is a short-circuit-free drop transition of 13 Hz -is. This results from the following parameters:

current 220 A tension 38 V Gas from line 57 CO ₂ ; 15th Wire diameter 1 mm Wire type GRIDUCT

GRIDUCT S-V 10 batch 5885 (type designation of registration)

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Wire feed 10.65 m / min

Torch feed 100 mm / min

As the diagram shows, when the electrode wire end is applied with a pulsating gas flow in compliance with the above parameters and the following characteristic values for the pulsating gas flow, the drop frequency is greater namely proportional to the pulse frequency and the amount of gas the pulsating gas flow. With an increase in the gas pulse frequency from 10 Hz to 20 Hz, the drop frequency of about 17 Hz to 21 Hz, i.e. the frequency of 13 Hz present without a pulsating gas flow by 4 Hz (with a pulse frequency of 10 Hz) or. increased by 8 Hz (with a pulse frequency of 20 Hz).

The characteristic values for the pulsating gas flow are:

Gas type CO-

overpressure of the gas

in line 37 1.5 bar

Pulse duration td = ₂ y (see) f = gas pulse

frequency in Hz

Pulse pause tp = ₂ y (see)

Gas quantity 9 = Vf 6Ο 1Ο ~ ³ (l / min)

where V = stroke volume 6.5 cm

As studies have also shown, the drop frequency is also due to changes in the overpressure in the line 37 variable. At an overpressure of 2 bar and a gas pulse frequency of 22 Hz, a drop frequency of 22 Hz is reached, so one drop is advantageously detached per gas pulse even with these setting values.

The diagram also shows that the drop transition

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is controllable and controllable by the frequency of the pulsating gas flow.

In addition to gas-shielded welding under CO ₂ , the invention can also be advantageously used in arc welding under a different shielding gas, in plasma welding and in build-up welding.

Furthermore, the invention can also advantageously be used in combination with the pulsed arc welding described above, With the invention it can be achieved that the pulse current is smaller than the previous pulse currents and thereby the structure of such current sources is simplified. The invention also relates to welding processes applicable with discontinuous wire feed.

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Claims (1)

- 14 - / ■ - ■. Expectations Process for arc welding with a consumable electrode, in particular for gas-shielded welding under CO ₂ , characterized in that the consumable end of the electrode is of a predetermined frequency pulsating gas flow is applied. Method according to claim 1, characterized in that the pulsating gas stream has a frequency between approximately 1 and 200 Hz, preferably approximately between 1 and 50 Hz. Method according to Claim 1 or 2, characterized in that the pulsating gas flow is annular applied to the end of the electrode. Method according to one of claims 1 to 3, characterized in that the pulsating gas flow of is surrounded by a continuously flowing gas jacket. STPH / Be / Tr
10/17/1975
MG 688a 609821/0370 Blank page