The other is the laser welding method introduced in some areas mainly based on resistance stud welding - "alternating gantry welding". When the welding time exceeds 50% of the working time, the laser welding device is more economical. Laser tailor-welded laser tailor welded blanks have been widely used in the automotive industry. The use of laser tailor welded blanks not only reduces the manufacturing cost, logistics cost, vehicle weight, assembly tolerance, fuel consumption and scrap rate, but also reduces peripheral reinforcement. The number of pieces simplifies the assembly steps while improving the collision capability, stamping rate and corrosion resistance of the vehicle. In addition, it is also more environmentally friendly due to the avoidance of sealants.
In the automotive industry, welding is a key link. Appropriate welding methods have the advantages of improving the body's anti-collision capability, reducing the weight of the car body, manufacturing cost and fuel consumption, and simplifying the assembly process. Resistance bolting is one of the most common welding methods today, but experts predict that this method will be eliminated in the next 5 to 10 years, and metal-filled protective gas welding will lose its previous importance. In contrast, laser Welding has become a hot topic. For the traditional welding process that has been used for several years, it is difficult to improve its process, welding speed and quality; however, for laser tailor welding, there is a great room for improvement.
Laser welding
1. Process and necessary facilities
The laser (magnification of the light generated by the stimulated radiation) is a special kind of light, monochromatic and coherent, so that the light can be concentrated on a tiny spot where the steel melts. To create laser radiation, laser media is needed. The stimulated molecules can be produced while transferring energy from the outside to the inside. In the resonator, this monochromatic light will be reflected between the two mirrors, which produce time and spatially condensed photons, a partially transparent mirror that reflects the ray out of the resonator.
Laser tailor welding equipment
There are two important lasers for high power applications: carbon dioxide lasers and germanium: yttrium aluminum garnet lasers. The carbon dioxide laser is a gas laser, that is, the medium used to generate the laser radiation is a gas, and the stimulation process is a discharge process, and the wavelength of the carbon dioxide laser is 10.6 mm.é’•: The yttrium aluminum garnet laser is a solid-state laser, and the laser radiation medium is a lattice of germanium atoms in alumina. Since the density of the laser emitting atoms is relatively high, the size of the solid laser is smaller than that of the gas laser. The wavelength of the yttrium aluminum garnet laser is 1064 nm, which is one tenth of that of the carbon dioxide laser.
Carbon dioxide lasers are now more powerful lasers, but the é’‡: yttrium aluminum garnet laser control system is extremely advantageous. Since the carbon dioxide laser has a wavelength of 10.6 mm, a "steep slope" device must be installed, which limits the possible mode of motion. However, the yttrium aluminum garnet laser radiation can be guided by a flexible fibrous optical waveguide, thus allowing the laser emitting head to move freely.
2. Advantages and Requirements The most important advantage of laser welding is the ability to focus very high energy on a point where the laser beam strikes the edges of the two areas to be welded and the input energy heats the metal and melts it. After the laser beam is applied, the melted material will cool rapidly. In this process, a small amount will enter the part being welded. While the weld reduces thermal distortion, the input thermal energy is also reduced. Reducing deformation due to heat and increasing accuracy correction can save a lot of money and time.
However, how to increase welding speed and reduce low energy input is currently a challenge. The reduction of low-energy input in the heated area has its advantages: the complex steel shape of the pearlite, martensite and austenitic joint structure does not change the structure over a wide range, and this feature is equally applicable to other steels, such as IF steel is limited to carbon precipitation; but on the other hand there are some deficiencies, a small amount of energy will lead to rapid cooling, heat will be introduced into the cooling part.
To reduce the hardening of the seam, it is important to carefully adjust the welding speed parameters, laser power, cooling ratio and focus position. In order to prevent further hardening of the metal, it is also necessary to protect it with a protective gas such as argon gas and helium gas, which does not cause any thermal reaction in the material.
Another problem caused by the small spot size of the laser beam is the quality of the trimming. If there is a seam to be welded between the two parts, the laser beam is guaranteed not to come into contact with it and melt it. To avoid this, the accuracy of the parts is very high. At present, the more common use field is the long seam connecting two parts, which can be found in more and more body blanks.
Laser tailor welded blank
1. Advantages of laser tailor welded blanks German ThyssenKrupp Laser Tailored Blanks Co., Ltd. began to produce tailor welded blanks in 1985. The emergence of laser tailor welding technology has led to the shift of automobile manufacturing from vehicle manufacturers to material suppliers. At present, laser tailor welded blanks are mainly used in the automotive industry. In laser welding, the material is butted rather than overlapped, which will result in the following weld characteristics:
(1) reducing the volume of the weld zone, for example, the weld width does not exceed 0.5 ~ 1mm;
(2) does not increase the weld height;
(3) Less influence on press forming performance;
(4) After the galvanization is added to the weld, the cathodic protection function can be maintained;
(5) During the welding process, the heat affected zone is small.
After the welding is completed, the static and dynamic strength of the weld zone is a very important indicator. Therefore, it is necessary to sample the weld zone and perform a destructive tensile strength test (cup test) to test the tensile forming of the weld zone. performance. Generally, the tensile strength of the weld is higher than the strength of the base material.
The laser tailor welded blank process has many advantages compared with the traditional spot welding lap process: it not only reduces the manufacturing cost, logistics cost, vehicle weight, assembly tolerance, fuel consumption and scrap rate, but also reduces the peripheral reinforcement. The quantity simplifies the assembly steps and processes, and at the same time, the collision capability of the vehicle is enhanced, and the stamping rate and the corrosion resistance are improved. In addition, due to the avoidance of the use of sealant, it also benefits the environment.
2. The application of laser tailor welded blanks has been widely used in body parts. The latest research results of ULSAB (World Lightweight Steel Body Association) show that 50% of the latest steel body structures are used. Welding plate manufacturing.
Linear laser welding machine produced by ThyssenKrubno
When laser tailor welding technology is applied to the manufacture of the side wall of the vehicle, no need for any reinforcing bars, ribs and associated production processes, the weight and the number of parts will be reduced, and the application of high ductility materials will also make the impact resistance Improved. At the same time, the reinforcement plate is no longer needed. On the B-pillar, the application of the tailor-welded plate can greatly reduce the cumulative tolerance.
The use of laser tailor welded blanks not only improves the stability of the quality of the door parts, but also makes the adjustment of the door parts no longer a problem, and at the same time reduces the weight of the parts, and the sealing measures of the original joints are omitted. Make it more environmentally friendly. In addition, the application of the tailor welded blank on the door also strengthens the rigidity of the hinged area, and the tolerance of the door is greatly improved. When the weight is reduced and the production process is optimized, the cost is inevitably lowered.
The body strength and rigidity of the Audi A6 have been praised. The new Audi A6L has been re-improved on the basis of the original: the body design using laser tailor welding technology. The new Audi A6L's reinforced body has a 34% increase in torsional strength. With the new body and chassis design combined with the solid body structure using advanced laser welding technology, the new Audi A6L can predict passengers' deformation zone, side collision protection beam and reasonable interior space structure. Provide effective protection. These invisible designs and materials not only reduce the cost and weight of the vehicle, but also maximize the safety of passengers at critical times.
3. Quality Management (1) Welding Inspection Quality Inspection and Assurance System provides guarantee for the production of high quality tailor welded blanks. The production process of tailor welded blanks uses automated production lines to ensure safe and economical production. This requires modern testing instruments. . As early as 1985, the German ThyssenKrupp Laser Tailored Blanks Co., Ltd. began to use the monitoring system when it began to produce tailor welded blanks. Now, this system has been perfected. A weld monitoring system is installed behind the welding laser head to monitor the quality of the weld to ensure that the weld meets quality requirements. A plasma monitoring system is used to monitor the stability of the welding process, and a computer-aided system can process the signals provided by the sensor during the welding process.
Laser tailor welded blanks require a fully automated or semi-automatic economical production line, while modern technology is used to monitor the welding process and product quality. In order to meet the requirements of these new fully automated production processes for any splice plates, Thyssen Welding Technology GmbH, the research department of ThyssenKrupp Steel GmbH, ThyssenKrupp Laser Technology GmbH and Thyssen In the early stage, the company proposed different possibilities for automatic evaluation of weld quality and production process management, and the first laser tailor welded blank produced by the first laser tailor welded blank factory started to operate on the bottom plate of Audi 100. on. In recent years, this technology has been further developed and improved at different stages. It not only controls the welding process itself, but also evaluates the weld with the latest generation of technology developed from existing systems. Its monitoring system not only monitors weld geometry defects during high-speed welding, but also detects very small holes.
(2) Evaluation system Thyssen LAM (laser application management) combined with the weld inspection system can not only detect tendencies, such as irregular geometric gaps (slit incidence, edge displacement, root subsidence), but also detect A small degree of sputum, such as stomata and holes. The combination of light streaks and plasma sensor systems has been complemented by optimal conditions, so high measurement rates ensure safe detection of slight flaws at high welding speeds.
A computer-assisted evaluation system automatically evaluates sensor signals, including during the welding process. It is thus determined whether the conditions of the relevant measuring points meet the specified requirements or whether deviations in the quality of the seam have occurred. During the welding process, the temperature of the weld is registered by infrared measurements. The sensor data records evaluated for each splice board are stored in a short protocol, which means that the quality of the product is allowed to be documented.
Domestic FAW-Volkswagen brand new Audi A6L
A complete error detection system warns operators of all mechanical shortcomings that occur in fully automated welding facilities. This quality management and monitoring system has been expanded to include new equipment concepts for nonlinear laser welding production. The placement of the sensor in front of the weld head enables the detection of the joint edges of the sheet to be welded, which not only allows the exact location of the joint edges to be ascertained, but also allows for the measurement of overlap between the sheets. When the identified overlap measurement exceeds a predetermined limit, the operator will be warned and the gap will be automatically sorted out. In addition, with this device, the detection signal of the connecting edge is also used to accurately distinguish and adjust the laser beam connecting the edges.
4. Technology Trends Which method will laser welding technology be used in the future? There are two answers: one is evolution, and the existing technology is improved. This means that there will be a new laser source for the development of laser welding - fiber laser, which is a laser with a flexible fiber resonator, the input energy ratio is much higher than the output energy, the whole device will be compact. Another benefit of high-power fiber lasers is the construction of the module, many fiber resonators with a power of about 300 to 500 W. If a technical hole occurs, it is very easy to replace a suitable module. In this case, since the laser works for a long time, it is not necessary to equip a trained technician.
The other is the laser welding method introduced in some areas mainly based on resistance stud welding - "alternating gantry welding". When the welding time exceeds 50% of the working time, the laser welding device is more economical. In terms of applications, resistance stud welding is now being applied, and the solution to this problem is a laser with two welding arrangements. When one configuration of the weld is running, the other configuration moves the treatment head to the next weld position, after which the laser will be transferred to another weld configuration, a technique that has been introduced by ThyssenKrupp.
However, in addition to this, automotive manufacturers will also have completely new welding techniques that revolutionize the world of welding, such as friction welding. Its advantage is that it only needs to be able to weld the necessary low energy input of the two parts, and the heat deformation is low. Because the temperature is very low, the weld is not harder than the material. However, there are also deficiencies: high-strength pressure and rapid rotation requirements must be well fixed to metal parts. Currently, only a few companies use this technology to weld aluminum. But no matter from which angle, laser tailor welding technology will be the development direction of future body welding technology!
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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