Kunshan jour laser share: what are the advantages and disadvantages of laser welding technology?

Advantages of laser welding:

1. The heat input can be reduced to the minimum requirement, the metallographic change range of heat affected zone is small, and the deformation caused by heat conduction is also the minimum.

2. The welding process parameters of 32mm plate thickness single pass welding have been verified to be qualified, which can reduce the welding time of thick plate, and even save the use of filler metal.

3. There is no need to use electrodes, and there is no concern about electrode contamination or damage. Because it is not a contact welding process, the wear and deformation of the machine can be minimized.

4. The laser beam is easy to focus, align and be guided by optical instruments. It can be placed at an appropriate distance from the workpiece, and can be re guided between the tools or obstacles around the workpiece. Other welding rules can not play due to the above space limitations.

5. The workpiece can be placed in a closed space (under the control of vacuum or internal gas environment).

6. The laser beam can focus on a very small area and weld small and closely spaced parts.

7. It can be welded with a wide range of materials, and can also be bonded with various heterogeneous materials.

8. It is easy to carry out high speed welding by automation, and can also be controlled by digital or computer.

9. When welding thin material or fine diameter wire, there will be no trouble of remelting like arc welding.

10. It is not affected by magnetic field (arc welding and electron beam welding are easy), and can accurately align the weldment.

11. It can weld two kinds of metals with different physical properties (such as different resistance)

12. No vacuum or radiation protection is required.

13. If the perforation welding is used, the ratio of depth to width of the weld bead can reach 10:1

14. The device can be switched to transmit the laser beam to multiple workstations.

Disadvantages of laser welding

1. The position of the weldment must be very accurate and must be within the focus range of the laser beam.

2. When the fixture is used for the weldment, it must be ensured that the final position of the weldment is aligned with the welding spot impacted by the laser beam.

3. The maximum weldable thickness is limited, and the penetration thickness is far more than 19mm, so laser welding is not suitable for production line.

4. The weldability of materials with high reflectivity and high thermal conductivity, such as aluminum, copper and their alloys, will be changed by laser.

5. When welding with medium to high energy laser beam, plasma controller should be used to remove the ionized gas around the weld pool to ensure the re emergence of weld bead.

6. Energy conversion efficiency is too low, usually less than 10%.

7. The weld bead solidifies rapidly, which may cause porosity and embrittlement.

8. The equipment is expensive.

In order to eliminate or reduce the defects of laser welding and make better use of this excellent welding method, some hybrid welding processes with other heat sources and laser are proposed, including laser and arc, laser and plasma arc, laser and induction heat source hybrid welding, double laser beam welding and multi beam laser welding. In addition, various auxiliary process measures are proposed, such as laser wire filling welding (which can be subdivided into cold wire welding and hot wire welding), external magnetic field assisted enhanced laser welding, shielding gas controlled weld pool depth laser welding, laser assisted friction stir welding, etc.

(1) Power density. Power density is one of the most important parameters in laser processing. With higher power density, the surface layer can be heated to boiling point in microsecond time range, resulting in a large amount of vaporization. Therefore, high power density is beneficial for material removal processing, such as drilling, cutting and carving. For low power density, it takes several milliseconds for the surface layer temperature to reach the boiling point. Before the surface layer vaporizes, the bottom layer reaches the melting point, which is easy to form a good fusion welding. Therefore, in the conduction laser welding, the power density is in the range of 10 ^ 4 ~ 10 ^ 6W / cm ^ 2.

(2) Laser pulse waveform. Laser pulse waveform is an important problem in laser welding, especially for sheet welding. When the high-intensity laser beam hits the surface of the material, 60 ~ 98% of the laser energy on the metal surface will be reflected and lost, and the reflectivity changes with the surface temperature. During a laser pulse, the reflectivity of metal varies greatly.

(3) Laser pulse width. Pulse width is one of the important parameters of pulsed laser welding. It is not only an important parameter different from material removal and material melting, but also a key parameter determining the cost and volume of processing equipment.

(4) The influence of defocusing amount on welding quality. Laser welding usually needs a certain distance, because the power density of the spot center at the laser focus is too high, which is easy to evaporate into holes. The power density distribution is relatively uniform on the plane away from the laser focus. There are two defocusing modes: positive defocusing and negative defocusing. If the focal plane is above the workpiece, it is positive defocusing, otherwise it is negative defocusing. According to the geometrical optics theory, when the distance between the positive and negative focal plane and the welding plane is equal, the power density on the corresponding plane is approximately the same, but the shape of the weld pool is actually different. When defocusing is negative, a greater penetration can be obtained, which is related to the formation process of molten pool. The experimental results show that the material begins to melt when heated by laser for 50 ~ 200us, forming liquid phase metal and vaporization, forming commercial pressure steam, which emits dazzling white light at a very high speed. At the same time, the high concentration of vapor makes the liquid metal move to the edge of the molten pool, forming a depression in the center of the molten pool. When the negative defocusing occurs, the internal power density of the material is higher than that of the surface, and it is easy to form stronger melting and vaporization, which makes the light energy transfer to the deeper part of the material. Therefore, in practical application, negative defocusing is used when the penetration is required to be large; When welding thin materials, positive defocusing should be used.

Collapse to edit the application of this paragraph

Laser welding machine technology is widely used in high-precision manufacturing fields such as automobiles, ships, airplanes and high-speed railways, which has greatly improved people's quality of life and led the home appliance industry into the era of precision manufacturing.

Especially after the 42 meter seamless welding technology created by Volkswagen has greatly improved the integrity and stability of the car body, Haier Group, a leading household appliance enterprise, solemnly launched the first washing machine produced by laser seamless welding technology. The household appliance cherishes the progress of science and technology for the people, and the advanced laser technology can bring great changes to people's lives. With the continuous consolidation of the global brand position of washing machine, its leading role in the industry has begun to be fully displayed. However, with the support of laser welding machine technology, there will be a deeper reform in the home appliance industry. According to Haier's R & D personnel, the manufacturing technology of the inner barrel of the full-automatic washing machine on the market mostly adopts the "buckle" technology, and there will be gaps or unevenness at the junction of the inner barrel, resulting in low strength of the barrel and unnecessary wear of clothes. In order to further improve the reliability and refinement of the inner barrel, Haier washing machine takes the automobile and shipbuilding industry as the reference parent, and applies the laser seamless welding technology to the new products of uniform power washing machine, which avoids the generation of the gap and irregularity of the inner barrel, comprehensively improves the reliability of the product, and takes more care of the clothes at the same time. Due to the improvement of the strength of the inner barrel, the maximum speed of the uniform power washing machine in the dehydration process is 25% higher than that of the ordinary full-automatic washing machine, the dehydration efficiency is greatly improved, and the power consumption is less and the time is saved.

In addition, we also learned that the "high power laser welding machine technology" jointly developed by China and Germany shipbuilding industry ensures the safety of the ship and further strengthens the hull structure; In the aviation field, laser seamless welding technology has been widely used in the manufacture of aircraft engines. At the same time, the laser seamless welding technology of aluminum alloy fuselage can replace rivets, thus reducing the fuselage weight by 20%; China's high-speed rail has also introduced the laser seamless welding technology, which not only improves the safety performance, but also greatly reduces the noise, bringing a quiet and comfortable riding environment for passengers.

With the comprehensive development of science and technology, the continuous consolidation and application of laser welding machine technology has also led the global home appliance industry into a new era. The new technology is not only the upgrading of products, but also the display and application of more science and technology.

1. The technology of tailor-made laser welding has been widely used in foreign car manufacturing industry. According to statistics, there were more than 100 tailor-made blanks production lines in the world in 2000, and the annual output of tailor-made blanks for car components was 70 million, which continued to grow at a high speed. Passat, Buick, Audi and other imported models produced in China also adopt some cutting blank structures. In Japan, CO2 laser welding is used instead of flash butt welding to connect rolled steel coil in steel industry. In the research of ultra-thin plate welding, such as foil with thickness less than 100 μ m, it is impossible to weld, but it is successful by YAG laser welding with special output power waveform, which shows the broad prospect of laser welding. Japan has also successfully developed YAG laser welding technology for the first time in the world for the maintenance of steam generator tubes in nuclear reactors. In China, Su Baorong has also carried out laser welding technology for gears.

2. With the continuous development of science and technology in the field of powder metallurgy, many industrial technologies have special requirements for materials, so the materials manufactured by metallurgy and casting method can not meet the needs. Due to the special properties and manufacturing advantages of powder metallurgy materials, they are replacing the traditional metallurgy and casting materials in some fields, such as automobile, aircraft, tool and cutting tool manufacturing industry. With the development of powder metallurgy materials, the connection between powder metallurgy materials and other parts is becoming increasingly prominent, which limits the application of powder metallurgy materials. In the early 1980s, laser welding entered the field of P / M material processing with its unique advantages, which opened up a new prospect for the application of P / M materials. For example, the brazing method commonly used in P / M material connection is used to weld diamond. Due to the low bonding strength and wide thermal impact zone, especially the high temperature and high strength requirements, the solder melts and falls off, Laser welding can improve the welding strength and high temperature resistance.

3. In the automobile industry in the late 1980s, kilowatt laser was successfully applied in industrial production. Now laser welding production line has appeared in the automobile manufacturing industry on a large scale, which has become one of the outstanding achievements of the automobile manufacturing industry. As early as the 1980s, European automobile manufacturers such as Audi, Mercedes Benz, Volkswagen and Volvo of Sweden took the lead in using laser welding for roof, body, side frame and other sheet metal welding. In the 1990s, American general motors, Ford and Chrysler introduced laser welding into automobile manufacturing. Although it started late, it developed rapidly. Fiat of Italy uses laser welding in most steel plate assembly. Nissan, Honda and Toyota of Japan all use laser welding and cutting technology in manufacturing body panels. High strength steel laser welding assembly parts are more and more used in automobile body manufacturing because of its excellent performance. According to the statistics of the U.S. metal market, by the end of 2002, The consumption of laser welding steel structure will reach 70000t, three times more than that in 1998. According to the characteristics of large batch and high degree of automation in automobile industry, laser welding equipment is developing in the direction of high power and multi-channel. In terms of technology, Sandia National Laboratory of the United States and Pratt Witney jointly carried out research on adding powder metal and wire in the laser welding process. Bremen applied Beam Technology Research Institute of Germany has carried out a lot of research on laser welding of aluminum alloy body frame. It is believed that adding filler residue in the weld can help to eliminate hot cracks and improve the welding speed, To solve the problem of tolerance, the developed production line has been put into production in the factory of Benz company.

4. Laser welding is widely used in electronic industry, especially in microelectronic industry. Due to the small heat affected zone, rapid heating concentration and low thermal stress, laser welding has shown its unique advantages in the packaging of integrated circuits and semiconductor devices. In the development of vacuum devices, laser welding has also been applied, such as molybdenum focusing electrode and stainless steel support ring, fast heating cathode filament assembly, etc. The thickness of elastic thin-walled corrugated sheet in sensor or temperature controller is 0.05-0.1mm, which is difficult to be solved by traditional welding method. TIG welding is easy to weld through, plasma stability is poor, and there are many influencing factors. Laser welding has good effect and is widely used.

5. The laser welding of biomedical biological tissue began in the 1970s. Klink et al. And Jain [13] have successfully welded fallopian tubes and blood vessels with laser, and the advantages show that more researchers try to weld all kinds of biological tissue, and extend to the welding of other tissues. The research on laser welding nerve at home and abroad mainly focused on the laser wavelength, dose and its effect on functional recovery, as well as the selection of laser solder. On the basis of basic research on laser welding small blood vessels and skin, Liu Tongjun also carried out welding research on common bile duct of rats. Compared with the traditional suture method, laser welding has the advantages of fast anastomosis, no foreign body reaction in the healing process, maintaining the mechanical properties of the welding site, and the repaired tissue grows according to its original biomechanical properties. It will be more widely used in biomedicine in the future.

6. In other fields, laser welding is also increasing in other industries, especially in the welding of special materials. Many researches have been carried out in China, such as laser welding of BT20 titanium alloy, hel30 alloy, Li ion battery, etc, Glamaco coswig, a German glass machinery manufacturer, has developed a new laser welding technology for flat glass in cooperation with IFW joint technology and materials experimental research institute.

Fold edit the advantages of hybrid welding in this section

Laser hybrid welding technology has obvious advantages. For laser mixing, the advantages are mainly reflected in: larger penetration / larger gap welding ability; The toughness of the weld is better, and the lattice structure of the weld can be affected by adding auxiliary materials; There is no sagging phenomenon on the back of the weld during burn through; The scope of application is wider; With the help of laser replacement technology, the investment is less. For laser MIG hybrid welding, the advantages are: high welding speed; The welding depth is large; Less welding heat is produced; The strength of weld is high; The weld width is small; The weld has small protrusion. So that the stability of the whole system production process is good, and the availability of equipment is good; The workload of weld preparation and weld treatment after welding is small; The welding production time is short, the cost is low and the production efficiency is high; It has good optical equipment configuration performance.

However, the investment cost of laser hybrid welding in power equipment is relatively high. With the further expansion of the market, the price of power equipment will also decline, and the hybrid laser welding technology will be applied in more fields. At least laser hybrid welding technology is a very suitable welding process in the welding of aluminum alloy materials, and will become the main welding production tool in a long period of time.

Development status of this paragraph

Foreign laser technology and manufacturing industry are more developed. As early as the 1980s, they began to study how to apply modern laser technology in traditional manufacturing industry. The European Union, the United States and other western countries as well as Japan in Asia, with the help of their developed scientific and technological strength and good manufacturing foundation, and under the reasonable guidance and financial support of the government, laser welding technology has developed very rapidly. Especially after entering the new century, it has been able to see the application of laser welding technology in many manufacturing and other industries, including the electronic industry, the electronic industry and the electronic industry Shipbuilding industry, automobile industry and so on, can see the application of modern laser welding technology. And has initially formed the industry standard of welding technology, so that it can be applied in a reasonable and controllable range. At the same time, in order to further improve the welding efficiency and make the laser welding technology better applied in modern large-scale production, especially in large-scale manufacturing and construction industry, western developed countries are actively studying how to improve the efficiency of laser welding in recent years. Through the research of high-power laser, the realization of high-power laser welding technology is further promoted and realized, so it is true