RU2705827C1 - Method of nonconsumable electrode welding in atmosphere of protective gases - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to a method of welding with nonconsumable electrode in the medium of protective gases and can be used in aerospace engineering, shipbuilding and other industries for connection of parts from aluminum and titanium alloys, as well as alloyed steel. Method of nonconsumable electrode welding in protective gas medium includes supply of two gases: helium and argon, coaxially simultaneously by two flows, forming internal pulse flow from helium, and external constant annular flow from argon, wherein internal flow of helium is additionally compressed in convergent channel, generating compressed arc pulse, and external annular flow from argon, leaving nozzle, forms protective gas curtain.

EFFECT: increase in penetration depth with reduction of welding current, provision of stable and even penetration of edges along the whole length without sagging.

1 cl, 1 dwg

Description

The present invention relates to the welding of metals and alloys, namely to welding with a non-consumable electrode in a protective gas environment and can be used in aerospace, shipbuilding and other industries for joining alloy steel, aluminum and titanium alloys.

A known method of welding in protective gases using helium, argon and mixtures thereof. Gurevich S.M. Reference book for welding non-ferrous metals. - Kiev: Naukova Dumka, 1981. - 608 p.

Common features: the arc welding method is carried out using a non-consumable tungsten electrode and inert shielding gases.

The disadvantages of the method include the following: the use of argon for protection does not provide good penetration and high welding speeds, with an increase in the thickness of the metal there is a high probability of lack of penetration; The disadvantages of using pure helium are the high price and high gas consumption; when using a mixture of argon with helium, special equipment for mixing is required, and the gas flow rate requires adjustment, because Due to the difference in the densities of helium and argon, the argon flow meter does not accurately show the gas flow rate.

The closest analogue taken as a prototype is a method of welding in shielding gases with a variable pulsed supply of argon and helium R.G. Tazetdinov, O.M. Novikov, A.S. Persian, B.A. Khasyanov, E.N. Ivanov, L.T. Plaksina "Arc welding in shielding gases with alternating pulsed supply of dissimilar gases." Welding production 2012 No. 1, p. 38-41.

Common features of the method is the use of protective gases of helium and argon for welding with a non-consumable tungsten electrode.

The disadvantages of the method include the use of complex gas distribution equipment and the impossibility of obtaining pure helium or argon pulses for an arc discharge, since the previous gas will be present in the zone of the welding arc before supplying one of the gases, which means that there will be a mixture of gases in different proportions at every moment in time.

The objective of the proposed invention is to develop a method of welding in protective gases of helium and argon with the optimization of their use and to obtain a better welded joint.

The technical result consists in increasing the efficiency of the use of gases in welding, reducing energy costs, reducing the number of defects in welds and creating favorable conditions for the formation of a weld during crystallization.

The technical result is achieved by the fact that the method of welding with a non-consumable electrode in a protective gas medium comprising supplying two helium and argon gases, according to the invention, the gases are supplied to the welding zone coaxially simultaneously by two streams, forming an internal pulsed stream from helium, and an external constant annular stream from argon, moreover, the internal flow from helium is additionally compressed in the ductus channel generating a compressed arc pulse, and the external annular flow from argon, leaving the nozzle forms a protective gas curtain.

 When the stabilizing helium flow into the arc gap expires with short pulses, not only the penetration depth changes, but also the outline of the weld cross section due to the movement of the metal in the weld pool, the interaction of volume and surface forces, and the size and shape of the weld pool is determined by the quality of the pulses per unit time, the flow rate of the stabilized flow and the obtained thermophysical characteristics of the arc pulses.

Argon is fed into the torch simultaneously with helium in a constant mode and, passing through the annular channel in the burner body around the collet assembly at the nozzle exit, forms an annular gas curtain, providing stable protection of the weld pool and the heat affected zone from external influences. Partial ingress of argon into the arc gap contributes to the stable excitation of the arc at a lower open-circuit voltage of the welding source. The presence of argon in the pauses between helium pulses stabilizes the welding arc and positively affects the crystallization of the weld pool, smoothing the transitions of structural zones, forming a smooth transition from the weld metal to the base metal.

The presence of distinctive features allows us to conclude that the claimed invention meets the conditions of patentability "novelty".

        An additional comparative analysis of patent and scientific and technical information did not reveal sources containing information about the popularity of the set of distinctive features of the proposed method, which indicates its compliance with the criterion of "inventive step".

A diagram for implementing the proposed method is presented in FIG. 1, which presents: a power source (welding unit) 1 cylinder with helium 2; cylinder with argon 3; gas pulsator 4; burner 5; collet assembly 6, tungsten electrode 7; copper sleeve 8; ceramic nozzle 9; pulsed helium flow 10; closed ring curtain of argon 11; welding arc 12 and welded product 13.

The method is as follows. From a cylinder with helium 2 and argon 3, gas is supplied to welding unit 1. After the welding unit is turned on, 1 helium enters the pulsator 4, and argon into the burner 5. Next, the arc 12 is first excited in argon, and then after switching on the pulsator 4 The pulsed helium flow 10 enters the collet assembly 6 of the burner 5 and passes through the baffle of the sleeve 8 around the tungsten electrode 7, increases the flow velocity and, at the output, displacing argon from the arc gap, enters the welding arc 12, generating b more powerful arc discharge. As a result of this, the degree of ionization increases, the electron current increases, the plasma temperature increases, and the arc pressure increases. The use of an arc pulse with a higher concentration and greater heat transfer allows increasing the penetration depth with a decrease in welding current.

The process of penetration by a pulsed helium arc discharge ensures a stable and even penetration of the edges along the entire length without sagging. Helium, having high fluidity, penetrates end-to-end between the edges and provides protection and heating of the reverse side of the seam.

Argon, passing through the annular gap in the burner body 5 in the form of an external annular flow and partially falling into the arc gap between the electrode 7 and the workpiece, initiates ignition of the welding arc 12, and also forms an annular gas curtain 11 at the exit from the nozzle 9, providing high-quality welding protection product baths 13 and zones around it with increased resistance to various environmental influences.

The presence of argon in the pauses (gaps) between helium pulses stabilizes the arc and helps to create conditions for cleaning the weld pool, provides a smooth transition of various structural transformations at the time of cooling of the weld pool.

Thus, a method of welding using protective gases of helium and argon with a coaxial feed: the internal helium flow in a pulsed mode through the boiling channel and the external argon flow with the formation of an annular gas curtain provides a better connection at a lower cost.

The proposed method is implemented when welding samples of aluminum alloy AMg3. It was performed by automatic welding without a lining on a machine equipped with an ADSV-6M machine using a gas pulser of its own manufacture.

Welding modes and conditions:

- welded metal AMg3, sheet thickness 2 mm; without cutting edges with zero clearance;

- non-consumable electrode - lanthanum tungsten, diameter 2 mm;

- filler wire grade AMg3, diameter 1.6 mm.

Shielding gases:

- argon, gas consumption 4-5 l / min;

- helium gas flow rate of 2-3 l / min - supply pulse duration of 0.5 seconds, pause duration of 0.5 seconds.

After welding, an external inspection was carried out, control with measuring instruments, X-ray inspection, metallographic inspection and mechanical tests.

Control Results:

- seam width - not more than 10 mm;

- convexity of the seam 0.3-1 mm;

- the height of the convexity of the root of the seam of 0.4-0.8 mm;

- lack of fusion and cracks are absent, pores are absent.

With the help of this practical example, the possibility of defect-free welding of aluminum alloys with improved weld geometrical parameters, crushed structure, the absence of internal defects, oxide inclusions and microcracks and improved mechanical properties was demonstrated.

Claims (1)

A method of welding with a non-consumable electrode in a shielding gas medium, comprising supplying two shielding gases in the form of helium and argon, characterized in that the gases are coaxially fed simultaneously by two streams, wherein an internal pulsed stream of helium is formed, which is additionally compressed in a confuser channel, and then generated a compressed arc pulse, and an external constant annular flow is formed from argon, through which a protective gas curtain is created at the exit from the nozzle.

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