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3DEVELOPMENT OF TECHNOLOGICAL EQUIPMENT FOR WELDING HIGH-PRECISION THIN-WALLED PRODUCTS FROM ALUMINUM ALLOYS USING A LASER HEATING SOURCE
Korzhyk V.,
The Paton Electric Welding Institute of the NASU, Kyiv, Ukraine
Kvasnytskyi V.,
NTUU "Sikorskys Kyiv Polytechnic Institute», Kyiv, Ukraine
Peleshenko Sv.,
NTUU "Sikorskys Kyiv Polytechnic Institute», Kyiv, Ukraine
Khaskin V.,
The Paton Electric Welding Institute of the NASU, Kyiv, Ukraine
Illyashenko Ye.,
The Paton Electric Welding Institute of the NASU, Kyiv, Ukraine
Lepilina K.,
NTUU "Sikorskys Kyiv Polytechnic Institute», Kyiv, Ukraine
Aloshyn A.,
The Paton Electric Welding Institute of the NASU, Kyiv, Ukraine
Aloshyn A.
The Paton Electric Welding Institute of the NASU, Kyiv, Ukraine https://doi.org/10.5281/zenodo.7258962
Abstract
The work is devoted to the creation of a technological complex for welding high-precision thin-walled aluminum products using laser radiation under conditions of a controlled atmosphere. The created research and industrial technological complex of equipment is described, which includes a welding vacuum chamber with systems for fastening, moving and welding the workpiece, a welding power source with a plasma module, a control system, vacuuming, gas preparation and purification of waste gases, as well as a glove chamber for manual assembly of product parts under welding. Two welding heads have been designed and manufactured for the welding of high-precision aerospace products from light alloys: a laser and an integrated laser with microplasma heating. The main characteristics of the technological laser and the power source of the microplasma part have been selected.
Keywords: laser welding, co-heating, microplasma, aluminum alloys, thin-walled structures.
For the manufacture of lightweight structures with high strength and corrosion resistance in modern industry, aluminum alloys are widely used. Such structures, first of all, include thin-walled products of the aerospace industry [1]. In the manufacture of such products, the problem often arises of making high-quality permanent joints [2]. For this, both traditional and new welding methods can be used [3]. In the case of manufacturing thin-walled one-piece structures, it is advisable to use such welding methods that provide local thermal heating of the weld zone. For example, laser, plasma or hybrid laser-arc welding methods [4].
To implement such welding methods, it is necessary to develop appropriate technological equipment. For each type of product range to be welded, this equipment may have a separate specialized design. The need to provide good protection of the weld pool [5] is one of the common moments in the creation of technological equipment for welding thin-walled aluminum products. One option for improving protection is the use of a controlled atmosphere chamber, which can also be a vacuum chamber [6]. Thus, it is relevant to create a technological complex for welding thin-walled aluminum products using laser radiation in a controlled atmosphere.
The purpose of the work is to create a technological complex for welding high-precision thin-walled aluminum products using laser radiation in a controlled atmosphere.
To achieve this goal, the following tasks were solved:
- selection of a technological laser, auxiliary power sources (including TIG welding power source), control systems, cooling and gas supply;
- development of heads for welding aluminum alloys using laser radiation;
- development of a controlled atmosphere chamber;
- development of a technological complex for welding aluminum alloys under controlled atmosphere conditions.
As a rule, aluminum products used in aircraft and rocket manufacturing have a wall thickness of up to 23 mm. For welding aluminum alloys of such thicknesses, it is advisable to use a fiber laser with a power of up to 2.0 kW. To improve the quality of welded joints, it is advisable to use concomitant microplasma heating. This will reduce the laser radiation power to 1.0 kW [4]. This will add a TIG welding power source, designed for currents up to 80-100 A, as well as a plasma module that generates a pilot arc with a current of about 10 A.
In order to perform welding of high-precision thin-walled products of the space industry from light high-strength alloys, an installation was designed, which consists of a vacuum chamber with systems for fastening, moving and welding the workpiece, a welding
power source, control systems, vacuuming, gas preparation and exhaust gas purification (Fig. 1). Let's consider the main nodes of this system in more detail.
Fig. 1. The appearance of the research and industrial complex for welding thin-walled products of the space industry from light high-strength alloys.
The vacuum chamber 1 of the welding installation with the help of supports 2 is based on the frame 3, which is installed on shock-absorbing supports 4 (Fig. 2, a). Chamber 1 is connected to the vacuuming, gas preparation and waste gas cleaning systems using flange 5. To change the parts to be welded, chamber 1 provides a hermetic door 6 with a visual observation window 7. The door is fixed on hinges 8 and has locking fasteners 9, which ensure a vacuum-tight fit of the door 6 to the body of chamber 1. In addition to window 7, there is a window for the pyrometric system 10, which is designed to monitor the temperature change of the welded part. In the lower part of the chamber 1, there is a drive 11 for rotating the part to be welded. On the upper wall of the chamber 1 there is a system 12 for guiding the joint of the welding head 13, which is based on one of the 3 interchangeable welding heads designed for the implementation of welding processes (laser welding in a vacuum and controlled argon environment and hybrid laser-microplasma welding). Specialized connectors 14 are used to connect additional vacuum, gas and electrical communications.
Inside the chamber 1, the part 16, which is welded, is based on the rotator 15 (Fig. 2, b). The rotator 15 has a system of vertical movement 17, which serves to change the parts to be welded. In the upper part of the part 16 around the welding zone, there is a gas blowing system 18, which serves to cool the part being welded. Inside the camera 1, under the upper wall, there is a camera lighting system 19. The shape of the chamber 1 ensures easy cleaning of the internal surfaces from welding aerosols and minimizes the number and size of hard-to-reach places where these aerosols can accumulate.
The operation of this installation is as follows (Fig. 2). After the part 16 to be welded is located in the rotator 15, the cover 6 is closed and sealed with fasteners 9. Through the flange 5, air is pumped from the chamber 1. After that, the laser welding process can be carried out in a vacuum or an inert gas (argon) environment. The laser welding process with accompanying microplasma heating is conducted exclusively in an inert gas (argon) environment. Therefore, if necessary, the chamber 1 is filled with argon under the required pressure through the fitting 14.
Fig. 2. 3D model (a, b) and external appearance (c) of the installation for welding high-precision thin-walled products of the space industry from light high-strength alloys in a controlled atmosphere of inert gases.
The part 16 is rotated at the required speed with the help of the rotator 15. By visual observation through the porthole 7 with the help of the system 12, the welding head 13 is guided to the joint being welded with the required accuracy. After that, the welding process is carried out. During the welding process, the temperature of the part 16 is constantly monitored by the pyrometer 10. If the temperature rises above the critical level, the gas blowing system 18 is turned on and excess heat is removed.
After welding, the rotation of the part 16 is turned off, the contaminated shielding gas is removed from the chamber 1, atmospheric air enters the chamber, the door 6 is opened, the rotator 15 with the part 16 is lowered down using the system 17, and the welded part is removed. Contaminated shielding gas is cleaned by a filtration system and can be reused or released into the atmosphere. A new workpiece is placed in place of the welded part in the rotator 15, the rotator rises, the work-piece takes its place in the cooling system 18 and the process is repeated.
To perform welding of high-precision thin-walled products of the space industry from light high-strength alloys, it is advisable to use two replaceable welding
heads - laser and hybrid laser-microplasma. Let's consider them in more detail.
The laser welding head is connected to the optical fiber connected to the technological fiber laser using the connecting adapter 1 (Fig. 3, a). The main components of this head are a collimator 2, a radiation focusing system 3, a flange 4 for attachment to the alignment system, a transition chamber 5, and a nozzle 6.
The radiation of the fiber laser, leaving the optical fiber, falls on the lens 7 of the collimator 2 (Fig. 3, b). This lens is preset and provides a parallel beam of radiation that is directed to the lens 8. This lens focuses the laser beam on the parts to be welded. The position of the focal plane relative to the surface of the parts to be welded can be changed due to the vertical movement of the lens 8 with the help of the focusing ring 9. To seal the transition chamber 5 and protect the focusing lens 8 from welding aerosols, a plane-parallel protective window 10, hermetically installed in the welding head housing, is used. The nozzle 6, located directly above the welding zone, is connected to the vacuum suction when welding in a vacuum or to the argon supply tube when welding in a controlled inert gas atmosphere. This allows you to minimize the harmful effect of welding aerosols on the protective window 10.
Fig. 3. Laser head for welding in a protective argon atmosphere.
The head for hybrid laser welding with accompanying microplasma heating consists of laser part 1 and microplasma part 2 (Fig. 4). The laser part is a housing with an internal channel 3, which is attached to the laser head instead of the transition chamber (Fig. 3) with the help of a union nut 4. The microplasma part in its essence corresponds to the design of a conventional microplasma head, except for the protective nozzle, which
is unnecessary due to the presence of a protective chamber. The main difference is the inclined location of the tungsten electrode 5, which is associated with the need to vertically feed the laser radiation to the product being welded. The connection of electricity, water and gas communications is similar. Focused laser radiation and a compressed microplasma arc are output to the part to be welded through a common nozzle 6.
Fig. 4. Hybrid laser-microplasma head for
The action of the hybrid laser-microplasma welding head occurs in the following way (Fig. 4). After positioning the head along the axis of the welded joint, plasma-forming gas is supplied and another arc is ignited between electrode 5 and nozzle 6, which is blown out of nozzle 6 by a stream of plasma-forming gas in the direction of the part being welded. After that, the main arc is ignited between the electrode 5 and the part, and laser radiation is delivered simultaneously. The process of hybrid laser-microplasma welding is performed. Cooling of the microplasma part of the head during adjustment and welding is permanently on.
Conclusions.
1. A research and industrial technological complex of equipment has been developed, which includes a welding vacuum chamber with systems for fastening, moving and welding the workpiece, a welding power source with a plasma module, a control system, vacuuming, gas preparation and purification of waste gases, as well as a glove chamber for manual assembly of product parts under welding.
2. Two welding heads were designed and manufactured for the welding of high-precision aerospace products from light alloys: a laser and an integrated laser with microplasma heating. The main characteristics of the technological laser and the power source of the microplasma part have been selected.
welding in a controlled inert gas atmosphere.
References:
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