SU1694360A1 - Method and apparatus for argon arc welding of aluminium and its alloys by asymmetrical current with non-consumable electrode - Google Patents

Description

one

(21) 4623661/27

(22) 12/21/88

(46) 11/30/91. Bul №44

(72) D.V.Gukov, V.A.Dvinin and V.P. Nagnibed

(53) 621.791.75 (088.8)

(56) USSR Copyright Certificate No. 1623844, cl. At 23 K 9/10. 1988

(54) METHOD OF ARGON-ARC WELDING BY ASYMMETRIC CURRENT BY NON-SWIMMING ELECTRODE OF ALUMINUM AND ITS ALLOYS AND DEVICE FOR ITS IMPLEMENTATION

(57) The invention relates to welding and may be applied in various industries. The purpose of the invention is to improve the quality of welded joints. The essence of the welding method is that before using the welding current source, it is set up to work with products of a certain alloy of different thickness. With

this, by means of a tuned device, for each of the entire range of effective values of the welding current, fix the corresponding value of the constant component of the current. By a smooth variation of the constant component at a constant current value of the welding current, a stable mode is found in the current oscillogram, close to the occurrence of half-waves of current of reverse polarity. During operation, the arc melting capacity required for the product to be welded is set by combined regulation of the effective value and constant component of the welding current and welding is performed. The device includes a welding transformer with counter-parallel thyristors in the secondary winding, an exciter-stabilizer arc, a set of resistors connected to a multistage two-section switch. 2 sec. f-ly, 2 ill.

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The invention relates to welding and can be applied in various fields of industry.

The purpose of the invention is to improve the quality of welded joints of products from aluminum and its alloys.

FIG. 1 is a schematic diagram of a device for argon-arc welding; Fig. 2 shows the zone indicated by dashed lines, the ratios between the effective value of g and the constant component of the welding current 0. These values are fixed with the help of a trimmer during the implementation of the method for their technical products.

AD1 aluminum of various thickness, Weld edges before welding are cleaned, and the welding conditions are as follows: welding speed 10 ± 2 m / h; EVL electrode with a diameter of 4 mm; nozzle inner diameter 15 mm; argon consumption 18-20 l / min; arc gap length 3 ± 1 mm.

The device for argon-arc welding (Fig. 1) consists of a welding transformer 1 (type TD-500), the secondary winding of which includes counter-parallel thyristors 2 (of the type T-500) with the opening time control circuits 3, high-voltage pulsed exciter - stabilizer 4 arcs (type VSD-01), including

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in the welding chain. Its pulses are synchronized with the moment of opening of thyristors 2 by voltage across the arc gap. Additional trimmer 5 includes a two-section multistage switch b and a set of trimming resistors 7 (type PPZ-43 0-6.8 kΩ), the number of which is equal to twice the number of steps of the switch Parallel arc gap connected resistor 8.

The resistor 8 (Fig. 1) is applied in the example of a specific implementation of the device for creating a current path supplying the thyristor control circuit 3 with a low conductivity of the arc gap; maintaining the thyristors 2 in the open state until the conduction of the arc gap is created by impulse of the driver-stabilizer 4 of the arc. This is necessary, since without the preliminary opening of the thyristors 2, the possibility of pulse injection by the stabilizer-stabilizer 4 of the arc is constructively excluded, since it is controlled by the voltage across the arc gap.

When using thyristor control circuits 3 with auxiliary thyristors, the power of unproductive losses in the resistor 8 does not exceed 2 W,

It is possible to implement a device without a resistor 8, for example, using thyristor control circuits 2 powered by the primary voltage of a welding transformer and an arc stabilizer 4 exciter controlled by a pulse for opening thyristors 2.

For ease of understanding the operation of the device in the example of a specific implementation, the simplest control circuits of thyristors 3 and the simplest method of controlling the stabilizer-pathogen 4 (arc voltage) are applied. This necessitates a resistor 8.

Fig. 1 shows thyristor control circuits 3, each of which consists of series-connected resistors 9 (of the MLT-2 type 2000 m) and a zener diode 10, consisting of three series-connected zener diodes of the D815E, D815G, D815G types (35 V), connected by the free anode of the Zener diode 10 to the cathode of the thyristor 2. The free output of the resistor 9 is connected to the anode of the thyristor 2. The capacitor 11 (type MBM, 0.5 µF, 63 V) is connected in series with the distor 12 (type KN102B, 30 V). By a free cathode, a dynistor 12 is connected to the control electrode of the thyristor 2. The free capacitor 11 is connected to the anode of the zener diode 10.

Each circuit is connected to a section of the tuning device 5 by a common point of the capacitor 11 and the dynistor 12, and the anode of the zener diode 10.

Each section of the switch b is connected to its contacts by the adjusted resistors 7 connected to one control circuit 3 of its movable contact 13 and the free terminals of the adjustment resistors 7. The other leads resistors 7 are connected to the fixed contacts 14 of the switch 6. In any position of the switch 6 with control circuits thyristors 3 are connected two trimmers

5 resistors 7 not used in other positions of the switch 6, each of which determines the opening time of the thyristors 2, and together they determine the effective value and the constant component of the welding current.

In order to implement the method, before using the asymmetric current source, it is tuned using a trimmer and measuring devices.

5 devices - an oscilloscope with a shunt connected in series in the welding circuit to control the omission of a half-wave current of reverse polarity, an ammeter of the magnetoelectric system with a shunt in the circuit

0 welding to measure the DC component of the welding current 0 and ammeter of the electrodynamic system, specially calibrated for operation with a current transformer, the magnetic circuit of which

5 has an air gap, which excludes the saturation of a ferromagnet, for measuring the variable component of current I.

The adjustment is made in the following sequence: set the switch 6 to the left end position; select the effective current value d, which is assigned to this position of the switch; Include a welding machine, ignite an arc on a thick aluminum plate; change the values of the trimming resistors 7, connected to the thyristor control circuits in this position of the switch 6, akim. equality to

0 - Vlt + lf.

The welder selects the thickness of the aluminum alloy plates for which adjustment will be made corresponding to the arc melting capacity, and

5 produces welding in a convenient mode (with the usual welding speed, arc length, using the specified electrode diameter and nozzle inner diameter). In this case, the presence of gaps of the half-wave current of oGps polarity is monitored.

waveform welding current. In the case of their presence, the values of the adjusted resistors 7 are smoothly changed so that, with a constant current value d, (i.e., maintaining equality d Vl + IQ) increases, the constant component of current 10 of natural polarity, i.e. . due to the difference in thermophysical properties of the non-consumable electrode and the product being welded.

If there are no gaps in the HALF-WAVE, the constant component 10 is reduced while the current value remains constant (a negative value of the constant component of the welding current is also possible). The selection is continued until such a constant component of the welding current 0 is established at a given effective value of it, d, which corresponds to a stable mode, close to the occurrence of half-waves of current of reverse polarity.

The omissions of the half-wave current may not occur in the following cases: electrode contamination, in which case it is necessary to burn contamination by initiating an arc on the coal plate; an excessively small diameter of the electrode, causing a high force effect of the arc and severe deformation of the surface of the weld pool and St. loans, with this dramatic deterioration of the conditions for cleaning the surface of the welding bath from oxides — while increasing the diameter of the electrode; low effective current value at specified other mode parameters — to apply the method, you need to change the mode parameters, for example, reduce the welding speed; a large thickness of oxides and contaminants on the surface of the metal being welded - for the application of the method it is necessary to be small, the same thickness of oxides and contaminants for products of different thicknesses, which is achieved, for example, by machining the welded surfaces of the products before welding.

Switch 6 is then set to the second (left) position and similarly adjusted for a larger effective value of the current by other trimming resistors 7 connected to the control circuit 3 in the second position of the switch 6. Thus, the whole range of modes is adjusted according to the number of steps of the switch.

The method was implemented in argon-arc welding with an asymmetric current with a non-consumable electrode with a diameter of 4 mm of products made from technical aluminum AD1 (whose weldable surfaces were cleaned before

welding) under the following conditions: welding speed 10 ± 2 m / h: burner nozzle inner diameter 15 mm; arc length 3 ± 1 mm: argon flow 18-20 l / min. The ratio between the constant component and the effective value of the welding current envy is selected according to the relationship shown in Fig. 2 (the area bounded by the dotted lines). If these conditions are observed, the oscillograms of the welding current show the absence of gaps of the half-wave current of the reverse polarity, and the welds are of good quality.

Compared to the prototype, the method implemented by the device for argon-arc-welding, improves the quality of welded joints by using modes with the highest possible amount of current of reverse polarity, which contributes to increasing the strength of welded joints. The absence of gaps in the half-wave current of reverse polarity does not cause fluctuations in the magnitude of the welding spattering current of the filler material at current surges caused by transients after the passage of the half-wave current. In this case, the welder does not require special knowledge and time to adjust the two quantities. It uses one combined regulator to select the desired arc melting capacity.

Introduction to the method of additional operation — setting up a source of sverbchny current by means of a trimmer, which is made once before operating the source, is economically feasible, since it reduces by more than 4 times the time required to establish the required welding current parameters, which is spent repeatedly labor productivity, improves the quality of welded joints.

A method and apparatus for carrying out the most effective e plant conditions when working with similar aluminum alloys of various thicknesses, for example, at the electric workshop, where welding of commercially pure AD1 aluminum busbars is mainly used. The use of several trimmers makes it possible to implement a method for welding various aluminum alloys.

Claims (2)

The formula is from 5 p o g e and 1. The method of argon-arc welding with an asymmetric current with a non-melting electrode of aluminum and its alloys, in which an arc is ignited, is set to the required welding current parameters for a specific product and welding at high currents and low speeds, characterized in that, in order to improve the quality of welded joints and facilitate the operation of the welding current source, the required welding current parameters are determined before using the welding machine for welded products made from one alloy and having different thickness, at the same time the constant component is smoothly changed at a constant current value of the welding current until a stable mode is obtained cooking close to the occurrence of the omissions of the half-wave current of reverse polarity, then fix for each of the effective values of welding current for a certain thickness, select the corresponding value of the constant component of the current, and during welding set the required parameters of welding current for a product of a certain thickness combined regulation of the effective value and constant component of the welding current. ,   3rd i jffi Kl 2. A device for welding by an asymmetric current with a non-consumable electrode of aluminum and its alloys, consisting of a welding transformer, the secondary circuit of which includes counter-parallel thyristors with control circuits of a high-voltage pulsed arc stabilizer exciter connected in series to the welding circuit, characterized by that it is equipped with a trimmer, including a two-part multistep switch and a set of trimming resistors that control the average current and reverse polarity, the number of which is equal to twice the number of switch stages, with the trimmer resistors being connected to one fixed contact with the fixed contacts of the switch, and each switch section with the adjusting device resistors connected to its contacts is connected to one of the thyristor control circuits with its movable contact and common point of the free pins of the trimming resistors-adjusters. YES) -BO FIG. 2