RU2332285C2 - Method of welding in protective gas with gas-dynamic removal of contamination layer from welding zone - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention pertains to welding of metals, particularly to methods of welding in a protective gas. A protective gas is supplied to the welding zone, and a pulse current is applied to the electrode. Simultaneously, a stream of auxiliary gas is directed to the contact zone of the electrode with the surface of the object. The auxiliary gas is supplied through a burner tip at 5 MPa pressure, in the form of an impact jet. Labour intensiveness of the process is reduced due to removal of the dielectric contamination layer from the surface of the object directly during the welding process.

EFFECT: reduced labour intensity of the welding process.

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Description

The invention relates to the field of metal welding, in particular to methods of welding in protective gas.

It is known that welding in shielding gas is widely used to restore faulty engine parts, transmissions, and chassis of automotive vehicles made of sheet steel, cast iron, non-ferrous metals, and alloys [1]. However, the surfaces of the parts to be welded are often covered with a layer of various contaminants: old coatings, residues of fuel and lubricants, corrosion products, bitumen deposits, soot. By their physical properties, these contaminants are dielectrics that prevent the excitation of the welding arc and the conduct of the welding process. The main disadvantage of the process of welding in shielding gas is that the parts at the welding site must be thoroughly cleaned of the layer of contaminants to ensure reliable contact of the welding electrode with the part. The operation to clean the welded surfaces from contamination is complex and time-consuming, requiring a lot of time and the use of special equipment [2]. A known method of cleaning the surface of products, taken as a prototype, however, it can be used as a preparatory operation before welding, painting, etc. and requires time, the use of additional energy-intensive equipment and special tools [3].

An object of the invention is to reduce the complexity of the process of welding in shielding gas.

The technical problem is solved due to the fact that simultaneously with the supply of a current pulse to the electrode and the shielding gas to the welding zone in the local zone of contact of the electrode with the surface of the part, the auxiliary gas flow under pressure of 5 MPa in the form of shock jets is directed through the tip of the burner.

The drawing shows the process of thermal destruction and removal of the contaminant layer from the welding zone with kinetic energy of the auxiliary gas stream, where it is indicated: pos. 1 - burner nozzle, pos. 2 - electrode, pos. 3 - contamination layer, pos. 4 - detail, pos. 5 - microprotrusions, pos.6 - channels for the passage of electric current, pos.7 - thermally destroyed pollution layer, pos.8 - shielding gas, pos.9 - auxiliary gas, pos.10 - burner tip.

The method of welding in protective gas with gas-dynamic removal of the layer of contaminants from the welding zone is as follows. In the initial period of the welding process, electrode 2 at the moment the contamination layer 3 is touched is supplied with a high current pulse with maximum parameters: current strength 800–900 A, voltage 60–80 V, pulse duration t _u = 1.5 ms, necessary for channel formation the passage of electric current 6 (breakdown of the dielectric) between the electrode 2 and part 4 through the microprotrusions 5. (figa). During thermal breakdown of the dielectric, the passage of current is accompanied by the release of "Joule heat", as a result of which the pollution layer is thermally destroyed (Fig. 1b). To remove the thermally destroyed layer of contaminants 7 in the local contact zone of the welding electrode 2 with the surface of the part 4 through the tip of the torch 10, at high pressure (≈5 MPa), an auxiliary gas stream 9 is introduced, which is simultaneously supplied shock jets, which, through the kinetic energy of the gas-dynamic pressure remove products of the thermally destroyed layer of contaminants from the welding zone (figv, 1d).

With the beginning of a stable welding process (Fig. 1d), the current and voltage automatically decrease to the operating mode, however, the heat generated by the welding arc and the thermal conductivity of the metal being welded are sufficient for further thermal destruction of the pollution layer in the welding zone. In this case, the removal of the thermally destroyed layer occurs by jets of auxiliary gas according to the scheme described above (Fig. 1c, 1d), and additionally by the gas-dynamic pressure of the welding arc.

Example 1. The restoration of parts with unprepared surfaces was carried out by welding, using a multifunctional welding complex that provides welding of parts made of cast iron, aluminum alloys, structural and alloy steels, in the MMA, MIG / MAG, TIG modes. By pulsed-arc welding, the KamA3-740 engine cylinder blocks (material - SCh-21 grade cast iron) were restored, having cracks on the side surfaces. Welding was carried out without cleaning the welded surfaces from old paint and a layer of contaminants. As filler material used wire Sv-08G2S with a diameter of 1.6 mm; welding speed 38 m / h, shielding gas — СО ₂ (flow rate 8–9 l / min), auxiliary gas — CO ₂ (supply pressure to the weld pool zone 5 MPa), welding current strength 80–100 A, arc voltage 18 V , current strength per pulse 600-700 A, pulse duration 2.0 ms, pulse frequency 50 imp / s, angle of inclination of the welding torch 70-80 °.

Example 2. Splices of cracks, holes, gaps in cabs, metal bodies, car frames and tracked vehicle bodies were welded. The surfaces of the listed parts were covered with a layer of old paint and solid particles of impurities (asphalt-bitumen substances), the total thickness of the layer of impurities was 0.5-0.7 mm. Cracks were welded in the following modes: pulse current amplitude of 750 A, current strength in pause of 160 A, arc voltage of 23 V, pulse frequency of 100 pulses / s, pulse duration of 2.5 ms, and welding speed of 19 m / h. Welding wire Sv-08G2S with a diameter of 1.2 mm, shielding gas - СО ₂ (feed pressure into the zone of the weld pool 5 MPa).

Thus, without the laborious preliminary operation — mechanical cleaning of the surfaces being welded from the dielectric layer — the welding process is ensured.

MMA - manual welding with a coated electrode,

MIG - inert gas welding with electrode wire,

MAG - welding in an active gas medium with electrode wire,

TIG - arc welding with non-consumable electrode in an inert gas.

Literature

1. Molodyk N.V., Zenkin A.S. Recovery of machine parts. Directory. - M.: Mechanical Engineering, 1989.

2. Volovik E.L. Handbook for restoration of parts. - M .: Kolos, 1981.

3. Description of the invention to the copyright certificate SU 1421249 A1, H05H 1/00. "Method for cleaning the surface of products", 10/30/1985, 5 l.

Claims (1)

A method of welding in shielding gas with gas-dynamic removal of a layer of contaminants from the welding zone, characterized in that simultaneously with the supply of a current pulse to the electrode and the protective gas to the welding zone, a flow of auxiliary gas is directed under a pressure of 5 MPa through the torch tip in the form of shock jets.