Effective Application of Laser Welding Technology in Automotive Manufacturing
Laser welding technology has the characteristics of high efficiency and good flexibility of welding process, in the process of automobile manufacturing, it can be used for welding of automobile body and welding of various types of automobile parts, reduce the overall weight of the automobile body, improve the precision of body assembly, meet the demand for automobile manufacturing lightweight and safety performance improvement, and at the same time, it can also reduce the cost of automobile manufacturing in the assembly cost and stamping cost, and improve the degree of integration of the car body. Therefore, how to actively and effectively apply laser welding technology has become the current automobile manufacturing enterprises need to consider the issue, the following will be a specific discussion on the application of laser welding technology.
1. Overview of laser welding technology
1.1 Laser welding technology principle
Laser welding, its essence belongs to the melt welding technology, with the laser beam as the main energy source, through a certain impact, complete the welding work of the weldment. The laser beam needs to be generated through the optical oscillator to achieve, high-power laser beam on the metal surface, can quickly vaporize the metal, when the molten metal liquid wrapped vaporization holes, can be in the stress reaction and heating and cooling methods, the formation of weld, and ultimately complete the welding of the metal. It should be noted that the laser beam has different densities at different powers, the depth of the weld also has an impact on the depth of the weld, as the laser beam density increases, will increase the depth of fusion, the weld is deeper. On the contrary, it will reduce the degree of depth of fusion, the depth of fusion is shallower.
1.2 Advantages and disadvantages of laser welding technology
Laser welding technology has the advantage of playing an important role in the current automobile manufacturing. Mainly in the following aspects: the actual welding is subject to a small range of heat influence, and the amount of deformation is also lower. Welding quality and precision is higher, can guarantee the aesthetic degree under the premise of quality assurance. Specific welding operation is more flexible, high efficiency, can meet the needs of enterprises. Construction noise is small, and has a good energy-saving effect. Applicable to brittle texture, high strength and high melting point material welding.
However, laser welding technology also has certain defects, which are as follows: high requirements on the welding position and the need to pay attention to the range of welding requirements. It is not suitable for materials with large thickness. When the welding material has high thermal conductivity, the welding effect will be affected. Energy conversion efficiency is low, while the solidification time of the weld channel is faster, to a certain extent, restricting the welding effect.
2. The practical application of laser welding technology
2.1 Laser self-melting welding
In laser welding technology, laser self-melting welding refers to two or more welding parts, in the melting and cooling process after cohesion into a whole, complete the effective welding. In the laser self-melting welding does not need to add flux can be completed welding, can save welding costs. Specific operation, under the action of the laser beam, so that the surface temperature of the welded part of the boiling point in a short period of time, the metal vaporization will generate a hole, as shown in Figure 1, in the recoil pressure of the metal vapor and the liquid metal surface tension, gravity to reach a state of equilibrium, the hole is no longer deepened, in the depth of a stable hole after the closure of the completion of the laser deep fusion welding. At present, in the automobile manufacturing, laser self-melting welding application is more extensive, often used in the body of the welding, group welding and parts of the welding. At present, the Volkswagen brand's Maiteng, Touguan and Sprint products, in the side of the welding in the fusion welding method. In some models of the logo and Citroen, the welding of the door is also used in the laser self-fusion welding. In addition, according to the type of welding seam classification, there are generally a variety of types such as single linear welding seam, plural and non-linear welding seam, etc. Due to the simplicity of the production process of single welding seam, it is now widely used.
Volkswagen in Germany in 1985, the earliest laser welding for Audi model chassis welding, Toyota in Japan in 1986, the use of add wire laser welding method for the body side frame welding. North America's high-volume application of laser welding technology in 1993, when the United States in order to improve the competitiveness of the United States automobile with the Japanese automobile and put forward the 2mm project. So far, almost all of the world's leading automobile manufacturers have adopted a large number of laser welding technology, involving automobile structural parts including the body side frame, door panels, windshield window frames, wheel cover panels, floor panels, intermediate pillars and so on.
The United States is also the earliest high-power lasers introduced into the automobile industry, in the United States automobile industry center in Detroit area there are dozens of laser processing station, used for automobile metal parts of the cutting and welding of gears, so that automobile restyling from 5 years to 2 years shortened. General Motors has used more than twenty laser processing production line, the United States Ford Motor Company used Nd: YAG laser combined with industrial robots to weld the sedan body, greatly reducing manufacturing costs, in 2000 the three major U.S. automobile companies have 50% of the resistance spot welding production line was replaced by laser welding production line.
In Japan, the successful application of laser welding in the production line for the world's attention, such as in the automobile body manufacturing in the implementation of laser welding of thin steel plate stamping molding of new methods, and now most of the world's automobile manufacturers to follow suit. Many famous automobile companies in the world have built special laser welding production lines: Thyssen Steel's car floor welding production line, Volkswagen's gear laser processing production line, Mercedes-Benz automobile factory's 18 plants in 8 of the plant installed laser processing equipment.
2.2 Laser Filler Welding
In laser welding technology, the principle of laser fillet welding is to add a specific welding material to the weld seam and form a welded joint by melting the filled welding material with the laser beam. Laser fillet welding has obvious advantages over traditional non-fillet welding methods, both in terms of expanding the range of laser welding and in terms of being able to weld thick plates at a lower power level and with a higher welding effect. It should be noted that, in the application of laser filler wire welding, not only to melt the wire, but also to melt the base material, so that the production of small holes in the base material so that the wire and the base material for the full fusion, to generate a new mixed melt pool. Mixed molten pool and the wire, the base material has a clear difference, can improve the base material itself exists some performance shortcomings, in the use of reasonable composition of the wire as filler material, to ensure that the weld has a high degree of wear resistance and corrosion resistance.
2.3 Laser arc composite welding
In laser welding, the principle of laser arc composite welding is to combine the laser heat source and the arc, in a molten pool together, and then realize the welding. The welding principle is shown in Figure 2, and the welding method is characterized by small deformation, high speed and high adaptability.
In the German Audi company series car production, laser arc composite welding process is applied to the most critical all-aluminum body welding. The car body is the second generation of the luxury Audi A8 series, which is designed for impact safety and resistance to twisting and deformation. The laser arc composite weld meets all the requirements and exhibits strong toughness, high strength and large depth of fusion. In order to meet the high customer expectations for this car, every detail has to be perfected to ensure the build quality of the car. The narrow weld seams of laser hybrid welding can be used for workpieces with high demands on appearance, then the corners at the top of the body frame do not have to be filled with plastic strips. In the field of light vehicle manufacturing, all the requirements mentioned above as well as some special conditions have to be met, and the manufacturing process of an all-aluminum body is even more stringent with regard to these requirements.
2.4 Laser remote welding
In laser welding technology, laser remote welding can be processed over long distances with the help of a high-speed scanning vibration lens to weld parts with laser beams of different powers. Because of its unique technical advantages, it is currently used in a large number of Mercedes-Benz panoramic sunroof and Volkswagen, Audi's side welding. In the current application of laser remote welding in automobile manufacturing, has the following advantages:
(1) has a strong positioning accuracy, can realize fast welding, to meet the manufacturing needs of automobile enterprises.
(2) Can be combined with different structural strength for welding, to realize the needs of different weld shapes.
Laser remote welding has high demands in terms of materials and equipment. When the thickness of the parts is large, it is impossible to reduce the depth of the weld, and the shear strength at the weld is low.
2.5 Laser brazing
In laser welding technology, laser brazing technology has the advantages of beautiful shape and strong sealing, and high strength of weld seam. The specific principle is to focus the laser beam on the surface of the welding wire, after melting the welding wire to fill in the welded parts, to brazing layer to complete the welding. Although this method is similar to fusion welding, the base material is not melted in practice. Therefore, the melting point of the brazing material needs to be lower than that of the base material, and effective soldering is realized by liquid brazing material. The principle is shown in Figure 3.
Laser brazing is currently used to weld luggage compartment lids in Volkswagen, Haima, Chery and Audi, and is also used from time to time to join roof and side panels in Cadillac, Porsche, Ford and Volkswagen. When using this technology, it is important to note that the welding process can be affected by many factors, especially the process parameters. For example, the welding speed, laser power and spot diameter need to be adjusted and designed in conjunction with the actual welding to ensure the effectiveness of laser brazing.
Equipment for laser brazing usually requires a brazing processing lens integrated into the robot arm. The laser beam is focused on the joints of the plates, melting a welding wire (e.g. copper-silicon wire) and thus joining the parts together. The success of this process is that it achieves a joint strength close to that of a weld, and it produces an aesthetically pleasing weld seam. The welds produced by laser brazing are known for their high sealing properties, smoothness and cleanliness. As a result, the brazed product requires little rework. For example, the bodywork can be painted directly after cleaning.
The usefulness of Laserline diode lasers in the field of laser brazing is highly valued worldwide. More than 800 LDF diode lasers are in successful long-term use in automotive body assembly applications around the world. High-quality laser brazing is not only characterized by high weld strength and low heat impact, but also by high demands on the aesthetics of the weld joint. A major processing advantage of the semiconductor laser is that it produces a stable molten pool. In addition, the three-spot module developed by Laserline offers further advantages in brazing applications: even when welding hard-to-braze hot-dip galvanized steel sheets, this technology enables high-quality weld joints without compromising on welding speed.
Laser brazing has long been a mainstream process in the production of car bodies. However, the increasing use of galvanized steel in car bodies has led to a number of problems: increased particle spattering during brazing and ripples at the wire joints, which have to be avoided by reducing the processing speed. laserline has developed a breakthrough solution to this problem: by using a multi-spot module, with the side spots in front of the main spot, the galvanized layer can be removed from around the weld first, making it possible to remove the galvanized layer from the weld. This makes it possible to remove the galvanized layer around the weld seam first, thus ensuring a smooth brazing process without having to reduce brazing speed. This process has been well received in the industry.
Conventional zinc galvanizing diode laser brazing uses single-spot technology. The laser source is integrated into the brazing robot. Due to the stabilization of the molten pool produced by the diode laser, laser cladding of silver or brass substrates is possible. The welds are aesthetically pleasing and of high quality. The operational stability of LDF diode lasers has been proven in series production by comparing a 4 kW YAG laser with a 6 kW diode laser for the brazing of a Volkswagen Touran in Wolfsburg, Germany.
3. Conclusion
For the automobile manufacturing industry, different laser welding technology has different utilization value. Different parts of the car to choose a reasonable welding method, is conducive to improving the overall quality of automobile manufacturing, and in the welding cost, welding efficiency to meet the needs of automotive enterprises. For this reason, this paper analyzes the principle and advantages and disadvantages of laser welding technology, explores the application effect of laser self-melting welding, laser wire-filling welding, laser arc composite welding, laser remote welding and laser brazing in automobile manufacturing, provides welding experience for automobile manufacturing, improves the welding level of automobile enterprises, and promotes the healthy and sustainable development of the automobile manufacturing industry. Translated with www.DeepL.com/Translator (free version)
