A device for arc welding bipolar rectangular current pulses

 

(57) Abstract:

The invention relates to welding equipment and can find application in the welding of aluminium and its alloys non-consumable electrode in inert gases. Output terminals of the main (5) a power source connected to the input terminals (8, 9) of the inverter. Output terminals (10, 11) of the thyristor inverter is connected to the arc gap. Additional source (6) DC one of its output terminals (10) is connected via a switch (7) from the output terminals (10, 11) of the inverter, and the other output terminal of the additional source (6) DC is connected to one of the input terminals (8) of the inverter. This embodiment allows the device to ensure the expansion of technological capabilities by way of separate regulation of the amplitude of the pulses of direct and reverse polarity. 5 Il.

The invention relates to welding equipment, namely, to the device power supply AC arc welding (mainly aluminium and its alloys non-consumable electrode in inert gases).

A device for arc welding with alternating current of a rectangular shape, including a step-down transformer, the power thyristor framework winding of the transformer, and outputs are connected in anti-parallel with respect to each other and in series with the power thyristor bridge and the load, i.e. the welding arc.with. 1542721 the USSR, MKI B 23 K 9/00, 9/10; publ. 15.02.90, bull. N 6). Among the advantages of such devices include simplicity of design and the separate regulation of the duration of the current pulse forward and reverse polarity. At the same time, it also has certain disadvantages. First, the highest frequency of the alternating current provided by the device is limited to the value of 25 Hz, for which changes in the process of adjusting the duration of half-periods is possible only in the direction of decreasing. Secondly, the proposed device provides only the modulation of the welding current in General, except for the separate regulation of the amplitude of the current pulse forward and reverse polarity.

Closest to the invention to the technical nature of the system is taken as a prototype.with. 1551484 the USSR, MKI B 23 K 9/00; publ. 23.03.90, bull. N 11). This device includes a main DC power source and the main thyristor inverter, as well as additional constant current source connected to the arc gap through will complete the highlighted its stability and weld quality. However, the design of the installation is also not possible to separately adjust the amplitude of the current pulse forward and reverse polarity, which significantly narrows the range of the parameters of welding and its technological capabilities.

The present invention is to improve the quality of welding thin materials by reducing the number of burn-through, increasing productivity welding of thin-walled products and increase durability nonconsumable electrodes.

The technical result is to expand the technological capabilities of the device for arc welding bipolar rectangular current pulses due to the separate regulation of the amplitude of the current pulse forward and reverse polarity.

The technical result is achieved in that a device for arc welding bipolar rectangular current pulses, including primary and secondary sources of direct current and thyristor inverter, whose input is connected to the main source, and access to the arc gap, an additional constant current source to one of its output terminals connected through a switch with the output terminals of the inverter, and the other output terminal of the addition, the address of the main and additional sources of DC power runs thus, that for one complete cycle of operation of the inverter main power supply generates in the welding circuit bipolar rectangular current pulses of equal amplitude, and an additional source it generates a unipolar rectangular pulses within a part of the operating cycle of the inverter corresponding to the pulse straight or reverse polarity (depending on switch position). In the result of summation of the pulses generated by the primary and secondary power sources, the curve of the welding current is an asymmetrical amplitude bipolar current pulses of rectangular shape. The magnitude of the current pulse forward and reverse polarity is set by setting the primary and secondary sources, DC, and their duration is set by the setting control unit thyristors of the inverter. Thus, the proposed device makes it possible to separately control both the activity and the amplitude of the current pulse forward and reverse polarity, which allows for more fine tuning of the equipment and makes welding more flexible. This provides you with additional control preplasma the ability of the arc as the cat is obedennyi applicant analysis techniques, including searching by the patent and scientific and technical information sources and identify sources that contain information about the equivalents of the claimed invention, has allowed to establish that the applicant is not detected similar, characterized by signs, identical to all characteristics of the claimed invention, and the definition from the list of identified unique prototype, as the most similar set of features analogue, has identified a set of essential towards perceived by the applicant to the technical result of the distinctive features in the claimed object set forth in the claims.

Therefore, the claimed invention meets the requirement of "novelty" by applicable law.

To verify compliance of the claimed invention to the requirement of inventive step, the applicant conducted an additional search of the known solutions, in order to identify characteristics that match the distinctive features of the prototype of the characteristics of the claimed invention, the results of which show that the claimed invention is not necessary for the expert in the obvious way from the prior art.

Therefore, the claimed invention meets the requirements of the e chart current items and curve of the arc current.

The device (Fig. 1) contains a thyristor inverter, comprising SCRs 1 to 4, the main DC power source 5 and an additional constant current source 6, a switch 7.

The output terminal of the main DC power source 5 is connected to the input terminals 8, 9 of the inverter. Terminal "minus" additional constant current source 6 is connected through the switch 7 with the output terminals 10, 11 of the inverter. Terminal plus an additional constant current source connected to input terminal 8 of the inverter. (And possibly another connection additional constant current source 6 to the inverter: the positive polarity through the switch 7 to terminals 10, 11 and the terminal minus - terminal 9). The output terminal 10 of the inverter is connected with a non-consumable electrode 12 and the output terminal 11 with the material being welded 13.

The device is in working condition and works as follows.

The base 5 and an additional 6 DC sources are connected to the light voltage and configured on the specified values of the current pulse forward and reverse polarity. Jumper switch 7 is set to the position "m", if you want more value current pulses of the opposite polarity is on power supply is shown in Fig. 2. In Fig. 3 shows a graph of the current through the thyristors 1, 4 up to an additional power source, and Fig. 4 is a graph of the total current through the thyristors 1 to 4. Chart measuring the arc current is shown in Fig. 5.

Let at time t1open the thyristors 1 and 3, through which, and through arc discharge, current flows from the main power source 5 (Fig. 2). Thus, the additional current source 6 will flow through the open thyristor 1 (Fig. 3) and an electric arc, and the current in the arc current pulse of reverse polarity is equal to the sum of the load currents of the primary 5 and 6 additional sources of DC (Fig. 5).

For time t2after completion of the switching processes (the switching nodes of Fig. 1 not shown), unlocks the thyristors 2 and 4, through which current flows from the main power source 5 (Fig. 2). When this current additional constant current source 6 flows through the thyristor 4, bypassing the arc gap. The magnitude of this current is equal to the amount of current short circuit the secondary circuit of the additional constant current source 6 and more current flowing from the secondary power source 6 through the thyristor 1 in the time period t1- t the primary DC source 5 (Fig. 5).

If you want to perform the welding arc with equal amplitude currents in pulses of direct and reverse polarity jumper 7 is set in the neutral position "n". The value of the arc current pulse forward and reverse polarity is equal to a load current of the primary DC source 5 (Fig. 2).

If you require larger values of the current in the pulse polarity, the jumper switch 7 should be set to the position "p". Thus, the additional current source 6 on straight polarity will flow through the open at this point, the thyristor 4 and the arc gap, and the reverse polarity, passing an arc through the open at this point, the thyristor 1. In the first case, the magnitude of the arc current in the pulse polarity is equal to the sum of the load currents of the primary 5 and 6 additional sources of direct current and pulse reverse polarity - load current of the main DC power source 5.

The welding arc is excited by any known method, and after the welding of quenched by disconnecting the unit from the mains, or any other known method.

When welding thin materials it is necessary to apply a variant according to which ri "m"). This preplasma ability of the arc is smaller, which reduces the possibility of burn-through and improves the quality of welding thin materials. At the same time, the arc will be quite stable due to the relatively large magnitude of the current pulses of the opposite polarity. In addition, at this ratio of current in pulses of direct and reverse polarity provides good conditions for cathodic cleaning aluminum materials from the oxide film, when welding thin sheet blanks is of paramount importance.

When welding thin sheet blanks when needed most preplasma ability of the arc, it is necessary to apply a variant according to which the magnitude of the arc current is less than the pulse polarity (jumper switch must be in position "p"). Thereby increasing the welding performance and increases the permissible current load on the nonconsumable electrode.

Testing of the developed device has shown the following.

The welding arc is easily excited and the device is illuminated over the entire range of changes in the duration (in experiments 1 to 20 ms) and current value (in the experiments from 20 to 300 A) pulse forward and reverse polarity. The current is regulated in castroni primary and secondary sources, DC (5 and 6). The application of the proposed device when welding thin-sheet aluminum alloys allows you to virtually eliminate the burns and, thereby, improve the quality of welded joints and welding thick plate of aluminum material provides increased depth of penetration, durability nonconsumable electrode and the performance of the process.

The above data confirm that the implementation of the use of the invention the following cumulative conditions: a tool embodying the claimed invention in its implementation, is intended for use in industry, namely in the field of welding, mainly aluminium and its alloys;

for the claimed invention as it is characterized in the claims, confirmed the possibility of its implementation using the above welding tools;

a means of embodying the invention in its implementation may be able to meet perceived by the applicant of the technical result.

Therefore, the claimed invention meets the requirement of "industrial applicability".

A device for arc welding of different rectangular impulit which is connected to the main source, and access to the arc gap, characterized in that the additional constant current source to one of its output terminals connected through a switch with the output terminals of the inverter, and the other output terminal of the additional constant current source connected to one of the input terminals of the inverter.

 

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