RU2732256C1 - Method of laser welding of metals and device for implementation of method - Google Patents

Abstract

FIELD: methods and devices for metal processing.

SUBSTANCE: invention relates to laser welding of materials. Protective gas is additionally supplied to welding zone through additional annular channel in laser welding head. Long-wave laser beam is fed in pulses with variable duration of pulse and variable duty ratio through detachable nozzle installed in nozzle case. 80 % of shielding gas - nitrogen, argon or helium - is fed into the annular channel, and additional protective gas - 20 % of CO₂ carbon dioxide is supplied to the additional annular channel. Laser radiation power is 3000÷4000 W, speed - 0.0083÷0.05 m/s, pulse duration - 50÷90 ms, duty ratio - 10÷40 ms at welding of materials with thickness of 1–5 mm.

EFFECT: invention makes it possible, during laser welding, to increase the size of the laser beam spot to optimum parameters required for welding of metals.

1 cl, 3 dwg

Description

The method of laser welding relates to the field of processing materials with a laser beam, namely, to the processes of pulsed laser welding.

There is a known method for laser welding of sheet metal (patent RU No. 2638090, IPC V23K 26/20, V23K 28/00, published on 11.12.2017), including the impact of light pulses with a density of 103-104 W / cm ² on metal thin films, when in which pulses of light radiation are created by means of a light source in the form of a translucent bulb filled with an inert gas and electrodes connected to pulse discharge electric energy storage devices, while the pulses of light radiation are focused on metal thin films at the contact point of two transparent rolls rotating in opposite directions , moreover, the repetition rate of the pulses of light radiation is from 10 to 50 Hz, and the speed of rotation of the rolls is selected from the condition that 5 to 10 pulses of light radiation hit the place of pressing the metal thin films. A device for welding thin-film metal products contains light sources and is equipped with transparent rolls rotating in opposite directions, while the light sources are made in the form of translucent flasks filled with inert gas with electrodes inserted through the ends of the flasks and connected to high-voltage discharge capacitors, which are equipped with reflectors focusing pulses of light radiation at the point of contact of metal thin films, while the light sources are located inside the transparent rolls.

However, the known method does not provide welding of thick materials, since the method is intended for welding thin-film products. In addition, the complex structure due to the rolls leads to a slowdown in the welding process and an increase in energy costs, equipment downtime is carried out.

There is a known method for laser welding (patent RU No. 2547987, IPC В23K 26/20, В23K 26/067, published on April 10, 2015), including the radiation of two laser beams along the fusion line from the side of the upper surface of the workpiece, while two laser beams are transmitted through different optical fibers and have focused spot diameters of 0.3 mm or more, wherein the laser beams are emitted in such a way that the leading laser beam of the two laser beams and the back laser beam of the two laser beams are tilted in the welding direction and at an angle with respect to to the direction perpendicular to the upper surface of the workpiece, the leading laser beam being positioned in front of the rear laser beam on the upper surface of the workpiece in the welding direction, and the rear laser beam being positioned behind the leading laser beam on the upper surface of the workpiece in the welding direction, and the angle of incidence of the leading laser beam is greater than that l Incidence of the rear laser beam.

A laser welding method, in which laser welding is performed by setting a gap between the center of the irradiated area of the upper surface of the workpiece that is irradiated with the leading laser beam and the center of the irradiated area of the upper surface of the workpiece that is irradiated with the back laser beam equal to 6 × D _max or less. D _max is the spot diameter, the largest among the diameters D _a of the leading laser beam spot and the diameters D _b of the rear laser beam spot, as well as with the setting of a gap between the center of the outgoing area of the rear surface of the workpiece, from which the leading laser beam exits, and the center of the outgoing area of the rear the surface of the workpiece, from which the rear laser beam comes out, so as to ensure it falls within the range from 2 × D _max to 12 × D _{max with} respect to the largest diameter D _{max of the} spot.

A laser welding method in which the angles of incidence of the leading laser beam and the rear laser beam are in the range of 5 ° to 50 °.

However, the known method is carried out with several beams, which complicates the optical part of the structure and requires a long adjustment of the optics and focus, which makes the process slow, and the device itself is expensive and is intended for welding thin sheets.

A known method for laser welding (patent RU No. 34427, IPC В23K 26/00, В23K 26/02, В23K 26/03, published on 10.12.2003), which can be used in various branches of mechanical engineering, jewelry and medical industries. The method is carried out as follows: building calibration curves of the dependence of the fraction of metal or alloy sprayed by laser radiation with a certain power level, retained by a liquid medium, practically transparent to laser radiation, on the depth of immersion in the liquid medium of the surface of the engraved metal or alloy. Then the cut metal or alloy is immersed in a liquid medium to a depth determined by the calibration curve. The metal or its alloy is penetrated along the welding line with a laser beam. Simultaneously with the translational movement of the laser beam, it is rotated with a radius R.

However, the known method is intended for welding thin products, is difficult to implement, but does not guarantee high strength characteristics of the weld, since the cooling time of the liquid metal is limited (several milliseconds).

A known method for laser welding of sheet metal (patent RU No. 2659503, IPC В23K 26/14 (2014.01) В23K 26/20 (2014.01), published 02.07.2018), the closest in technical essence and taken as a prototype, which can be used for point and seam welding of ferrous and non-ferrous metals with high oxidative activity without the addition of filler material. The laser welding head is fixed under the focusing lens of the laser welding machine, it contains: an annular nozzle for injecting a shielding gas, located on the same optical axis with the laser welding head and a protective chamber for protecting the focusing lens by means of a transverse air flow, while the chamber has an air inlet and air outlet matched to the air inlet in a plane that is substantially perpendicular to said optical axis, said air outlet being oriented in a direction opposite to the advancing direction of the laser welding head.

A method of laser welding using a welding head, characterized in that the laser beam is focused along the optical axis at a focal point located under an annular nozzle, while a shielding gas is injected around said focal point through said annular nozzle, and with the help of a transverse air flow in said shielding the camera is protected by a focusing lens and at the same time the laser welding head is moved along the seam perpendicular to the optical axis.

However, the known method does not sufficiently protect the weld by supplying only a single shielding gas - nitrogen, argon or helium. During the welding process, additional costs are required for cleaning the seam from the metal slag crust formed from the interaction of the liquid melt with the environment (air), the impossibility of welding materials with a thickness of up to 5 mm, as well as the use of filler material, which leads to widening of the weld.

The technical problem to be solved by the claimed method and device for implementing the method is the development of a method for laser welding of materials up to 5 mm thick.

The technical result, which the proposed method of laser welding and the device for implementing the method are aimed at, is to increase the strength and quality of the weld, the accuracy of focusing the laser beam, and to reduce energy consumption.

The technical result is achieved in that in the method of laser welding of metals with a welding head with a nozzle fixed under the focusing lens, including an annular channel for injecting a protective gas, located on the same optical axis with the aforementioned nozzle, in which, simultaneously with the laser beam, the annular channel is supplied with compression jets of shielding gas, new is that the welding zone is additionally supplied with shielding gas through an additional annular channel in the nozzle body, while the long-wavelength laser beam is pulsed with variable power, variable speed, variable pulse duration and variable duty cycle through a removable nozzle installed in nozzle body.

80% of a protective gas - nitrogen, argon or helium - is fed into the annular channel, and an additional annular channel is supplied with an additional protective gas - 20% of carbon dioxide CO ₂ , while the laser radiation power is 3000 W ÷ 4000 W, the speed is 0.0083 m / s ÷ 0.05 m / s, pulse duration - 50 ms ÷ 90 ms, duty cycle - 10 ms ÷ 40 ms when welding materials with a thickness of 1 mm to 5 mm.

The technical result is achieved by the fact that in a device for implementing the method, comprising a welding head with a nozzle fixed under the focusing lens, including an annular channel for injecting a protective gas located on the same optical axis with the aforementioned nozzle, it is new that an additional an annular channel for supplying additional protective gas, concentrically located relative to the above annular channel and a nozzle, in which a converging removable nozzle is installed.

The welding head is equipped with a sensor for setting the nozzle relative to the surface of the elements to be welded and controlling the size between the nozzle exit and the parts to be welded.

To obtain a given shape of a jet of laser radiation, a removable nozzle is made with a diameter in a narrow section of 1 ± 0.02 mm.

The distance from the nozzle exit to the parts to be welded should be equal to half the diameter of the removable nozzle to obtain optimal parameters of the focal spot.

Figure 1 shows a longitudinal section of a welding head.

FIG. 2 is an enlarged view B (Fig. 1) of a removable nozzle in the mode of welding metals with a thickness of 1 mm to 5 mm.

FIG. 3 shows view A of FIG. 1.

The welding head contains an outer casing 1, which is equipped with a cover 2 (Fig. 1). Inside the outer body 1 there is an inner body 3, to which the nozzle body 4 is attached (Fig. 1). Cuffs 5, fixed on the inner body 3 (Fig. 1) are designed to seal the cavity 6. The restricting ring 7 (Fig. 1) serves as a stop between the inner body 3 and the nozzle body 4. A removable nozzle 8 is attached to the nozzle body 4 (Fig. 1 ), which for welding modes of metals up to 5 mm thick has a diameter in a narrow section of 1 ± 0.02 mm. On the outer housing 1, below the nozzle 9, there is a sensor 10 (Fig. 1) for setting and controlling the size between the nozzle 9 and the parts to be welded 11, which is rigidly fixed to the bracket 12.

An annular channel 13 is made in the nozzle body 4, through which a protective gas flows - nitrogen, argon or helium, which is supplied through the fitting 14. Also concentric to the annular channel 13, an additional annular channel 15 is made, through which an additional protective gas flows - carbon dioxide, which is supplied through the fitting 16. The membrane 17 is attached with cuffs 5 (Fig. 1) to the inner surface of the outer housing 1 and the outer surface of the nozzle body 4. Figure 2 shows an enlarged view B (Fig. 1) of the removable nozzle 8 in the mode of welding metals up to 5 mm thick ...

The welding head works as follows.

The welding head is installed at a distance of 0.5 ± 0.02 mm from the parts 11 to be welded to increase the spot size of the laser beam to the optimal parameters required for welding metals. A laser beam is fed into the nozzle 9, which passes through the lens 18. The long-wave laser beam is pulsed to the parts 11 to be welded with a variable pulse duration and variable duty cycle, which passes through the lens 18 and exits through a removable nozzle 8 for melting the metal edges and blowing out the oxide film. During welding (Fig. 1), 80% of shielding gas - nitrogen, argon or helium is supplied to the annular channel 13 through the lower fitting 14 to protect the welded seam 19, as well as an additional 20% of carbon dioxide into the additional annular channel 15 through the fitting 16 for more effectively improve the strength, quality of the weld and reduce the heat affected zone. Shielding gases during the welding process are supplied simultaneously with the laser beam and protect the weld 19 from splashes and exposure to liquid melt with the environment (Fig. 1). Figure 3 shows a view A, where the removable nozzle 8 is inserted and there is a key hole 20 for inserting the removable nozzle 8 with screws.

Removable nozzle 8 (Fig. 1) will allow you to simultaneously clean the place of processing materials from the slag crust and improve the quality of the weld and the strength of the welded joint. The removable nozzle is fixed to the side of the nozzle with 9 screws.

Complete with laser technological complexes, the main technological indicators are provided at the level of: the roughness of the cut surface on titanium alloys not higher than 2 ... 4 microns, on stainless and high-alloy steels not higher than 10 ... 15 microns with a cut width of 0.1 ... 0.21 mm, the depth of the heat-affected zone is not more than 0.2 mm.

Technical characteristics, namely, variable welding speed plays a major role in the implementation of joining two workpieces: welding speed in the range from 0.0083 m / s to 0.05 m / s, since metal welding cannot be carried out below 0.0083 m / s, and in the case of a high variable speed, which is higher than 0.05 m / s, there will be incomplete penetration along the edges of the workpieces, as well as non-penetration of the root of the weld of metals from 2 mm to 5 mm. With a variable pulse duration, which is below 50 ms and a variable duty cycle, which is above 40 ms, the metal welding process is not feasible, since the lower limits do not allow melted metal fusion along the edges of the sheets, which cannot be called a welded joint. In the case when the variable pulse duration is above 90 ms and the variable duty cycle is below 10 ms, this means continuous penetration and non-penetration of the metal weld root from 2 mm to 5 mm.

In the mode of welding metals up to 5 mm, the intensity of laser radiation is set depending on the mode being performed and is 68 J / cm ² and 78 J / cm ² .

The welding head will allow welding up to 5 mm with high productivity, provided by changing modes during the pulse welding process. Shielding gases are supplied to the welding zone simultaneously.

The proposed method of laser welding allows to ensure efficiency, precision of laser welding, strength of the welded seam.

Claims (1)

A method of laser welding of metals, including the use of a welding laser head with a nozzle fixed under the focusing lens, in the body of which an annular channel for a shielding gas is made, and the supply of laser radiation and a jet of shielding gas to the welding zone, characterized in that an additional shielding gas is supplied to the welding zone gas through an additional annular channel made in the nozzle body, and the laser beam is supplied impulsively through a removable nozzle, which is installed in the nozzle, while nitrogen, argon or helium is fed into the annular channel in an amount equal to 80% of the shielding gas, and into the additional annular channel - carbon dioxide CO ₂ in an amount equal to 20% of shielding gas, while welding materials with a thickness of 1 to 5 mm at a laser power of 3000-4000 W, a speed of 0.0083-0.05 m / s, a pulse duration of 50 90 ms, pulse duty cycle 10-40 ms, and during welding, the distance from the nozzle exit to the parts to be welded is set equal to half the diameter removably th nozzles.

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