RU1776516C - Method of gas-shielded arc welding - Google Patents

Abstract

Usage: for arc welding with a non-consumable electrode with filler filing in shielding gases of parts of small thicknesses (up to 5 mm) of aluminum alloys, steels and other materials. The essence of the method: welding of parts of small thicknesses is carried out with a pulsating arc by a non-consumable electrode, and the welding arc is pulsed by a magnetic field generated by alternating current. In this case, the period of change in the magnetic field strength is at least 0.7 of the period of change in the welding current, and the duty cycle of the magnetic field pulses is selected in the range from 3 to 8.1 tables, 3 ill.

Description

The invention relates to welding and can be used for arc welding with a non-consumable electrode with filler filing in shielding gases of parts of small thicknesses (up to 5 mm) of aluminum alloys, steels and other materials.

A known welding method in which to ensure uniform formation and prevent burns during welding of small thicknesses using a pulsating welding current (Welding Handbook, edited by A.I. Akulov, v.1, Moscow, Engineering, 1978, p.145 -150).

However, the known method does not provide for the elimination of cracks, slag and oxide inclusions and porosity in the welds.

The closest in technical essence and achieved effect to the claimed is a method of arc welding controlled by a longitudinal magnetic field generated by alternating current, in which to improve the quality of welds, including the elimination of cracks, slag and oxide inclusions, the porosity of the welding the arc and metal of the weld pool are affected by an alternating longitudinal electromagnetic field (V.P. Chernysh et al., Welding with electromagnetic stirring. Kiev, Technique, 1983, pp. 11-20).

A disadvantage of the known method is the inability to perform welding of small thicknesses without burn-throughs, cracks, porosity and oxide and slag inclusions.

The aim of the invention is to improve the quality of welded joints of parts of small thicknesses by eliminating burns, cracks, porosity, oxide and slag inclusions.

The goal is achieved in that in the method of arc welding in shielding gases with a non-consumable electrode with filler metal supply, in which parts of small thicknesses (up to 5 mm) are welded by a pulsating arc, the welding arc is pulsed by a magnetic field.

XI X |

About joint venture

ON

generated by alternating current, while the period of variation of the magnetic field is at least 0.7 of the period of variation of the welding current, and the duty cycle of the pulses of the magnetic field is selected from 3 to 8.

As a result of the analysis of known methods of arc welding, when conducting patent research, technical solutions with a combination of features similar to the distinguishing features of the proposed method were not found.

The proposed method provides a positive effect, since it eliminates the formation of coolants, cracks, oxide and slag inclusions, porosity and improves the quality of welded joints.

The change diagram is shown in the drawings: in Fig. 1 - constant welding current, in Fig. 2 - alternating welding current, in Fig. 3 - magnetic field strengths in time.

The method consists in acting on a pulsating arc of alternating and direct currents and the metal of the weld pool and filler wire with a longitudinal magnetic field of N. The magnetic field is created by alternating current and is supplied in a pulse with a period of Tm. The period of variation of the welding current is Tcv. In this case, Tm 0.7 TSv, and the duty cycle of the magnetic field pulses is selected in the range from 3 to 8,

Point A on the current waveform corresponds to the beginning of a direct current pulse imp, point B to the end of the current pulse, the beginning of burning of the arc on duty dd, point C to the beginning of the end of one cycle of welding current change. Points Ai, Bi and Ci are respectively for alternating current. Point D corresponds to the beginning of a magnetic field pulse, point E corresponds to the end of a magnetic field pulse and the beginning of a pause, point F corresponds to the end of a cycle of a magnetic field change.

At 7 Tcv, non-uniform melting of the filler metal is observed and there are cases of cracks and oxide inclusions in the welds due to the short time of exposure to the magnetic field during periods of current pulses, when the magnetic field acts on the weld pool, and during periods of the arc when magnetic field facilitates the process of uniform melting of the filler metal

At Tm S 0.7 Tgv, there are no defects in the welds, since at the moments of pulses of the welding current l at the moments of burning of the pilot arc it is guaranteed to be provided by the action of the magnetic field on the weld pool and the molten filler metal.

Magnetic field impulse rate

determined from the relation o -. Exp

It has been experimentally established that with a pulse duration of Ti in the range of 0.6-0.8 s, and a pause of fn 0.1-0.2 s, effective grinding of the primary structure of the weld metal and oxide inclusions is ensured.

When the pulse duration is 0, b, 8 s, and pauses O, K mp 0.2 s, primary structure is not crushed

5 of the weld metal, which leads to the formation of cracks, especially at the end portions of the weld. In addition, complete destruction of oxide films is not ensured. In welds, oxide inclusions with a length of more than 3.0 mm are observed when welding parts with a thickness of 2.0 mm.

Example. Did automatic argon arc welding with a tungsten electrode of circular joints with a diameter of 80

5 mm, for which circular flat billets with a diameter of 80-0.1 mm thick were welded into flat billets 400x400x2 mm in size with a central hole of diameter 80 + 0.2 mm from aluminum alloy AMGB

0 2.0 mm. The welding current was varied from 90 A in the pulse to 40 A (duty arc). The welding speed (VCB) was 10 m / h. The pulse and pause durations were 0.5 s. To implement the method, a device consisting of a solenoid nozzle and a thyristor synchronous AC chopper was used. A magnetic field was applied with a frequency of 1.54-1.0 Hz and a duty cycle of ff 3-8.

0 To obtain comparative data, welding was also performed according to the prototype method.

Evaluation of welding methods was carried out on the basis of measuring the total length of oxide films and the presence of cracks. The presence of oxide films and cracks was determined by the results of X-ray diffraction, and the presence of external cracks and burns was visually determined using a magnifier with

0 tenfold increase.

The effect of magnetic field parameters on the quality of welds is shown in the table.

As can be seen from the table in the welds made according to the proposed method, there are no cracks, and the total length of oxide films is 5-6 times less than when welding by a known method

The proposed welding method provides efficient mixing

VA in the weld pool, destroys the oxide film on the surface of the filler wire, ensures uniform melting and leads to an increase in the quality of welds. This reduces labor costs for correction of defects by 1.5-2.0 times and increases the reliability of welded joints.

 FORMULA AND SECTION

Method of arc welding in shielding gases, in which the welding of parts of small thicknesses is performed by a pulsating non-melting arc

characterized by the fact that, in order to improve the quality of welded joints by eliminating burns, cracks, porosity, oxide and slag inclusions, the welding arc is pulsed by a magnetic field generated by alternating current, while the period of change in the magnetic the field is taken at least 0.7 from the period of variation of the welding current, and the duty cycle of the magnetic field pulses is selected in the range from 3 to 8.

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