What are the advantages and disadvantages of laser welding technology?

1, the heat input can be minimized, the metallographic change range in the heat affected zone is small, and the deformation caused by heat conduction is also the lowest.

The welding process parameters of 2.32mm thick single pass welding have been verified, which can reduce the time required for thick plate welding and even save the use of filler metal.

3. There is no need to use electrodes, and there is no need to worry about electrode pollution or damage. Moreover, 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, and can be placed at a proper distance from the workpiece and redirected between machines or obstacles around the workpiece. Due to the above space constraints, other welding rules can't work.

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

6. The laser beam can be focused on a small area, and small and closely spaced parts can be welded.

7. There is a wide range of solderable materials, and various heterogeneous materials can also be bonded to each other.

8. It is easy to carry out high-speed welding with automation, and it can also be controlled by numbers or computers.

9. When welding thin materials or thin diameter wires, there will be no reflow problem like arc welding.

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

1 1. Two metals with different physical properties (such as different resistances) can be welded.

12, no vacuum and no radiation protection.

13. If perforation welding is adopted, the depth-width ratio of the weld can reach 10: 1.

14. The equipment can be switched to transmit laser beams 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 weldment needs a fixture, it must be ensured that the final position of the weldment is aligned with the solder joint to be impacted by the laser beam.

3. The maximum weldable thickness is limited, and the workpiece with penetration thickness far exceeding 19mm is not suitable for laser welding on the production line.

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

5. When welding with medium and high energy laser beam, plasma controller should be used to drive away ionized gas around the molten pool to ensure the reappearance of weld.

6. The energy conversion efficiency is too low, usually lower than 10%.

7. The weld solidifies rapidly, and porosity and embrittlement may occur.

8. The equipment is very expensive.

In order to eliminate or reduce the defects of laser welding and make better use of this excellent welding method, some composite welding processes with other heat sources and lasers are proposed, including laser and arc, laser and plasma arc, laser and induction heat source composite welding, double laser beam welding and multi-beam laser welding. In addition, various auxiliary technological measures are put forward, such as laser wire filling welding (which can be subdivided into cold wire welding and hot wire welding), laser welding assisted by external magnetic field, laser welding with shielding gas to control the depth of molten pool, laser-assisted friction stir welding and so on.

(1) power density. Power density is one of the most critical parameters in laser processing. At high power density, the surface layer can be heated to boiling point within microsecond time range, resulting in a large amount of vaporization. Therefore, high power density is beneficial to material removal processing, such as punching, cutting and engraving. For low power density, it takes several milliseconds for the surface layer to reach the boiling point, and before the surface layer is vaporized, the bottom layer reaches the melting point, which is easy to form a good welding. Therefore, in conductive laser welding, the power density is in the range of10.4 ~10.6 w/cm 2.

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

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

(4) The influence of defocusing on welding quality. Laser welding usually needs some separation, because the power density of the spot center at the laser focus is too high and it is easy to evaporate into holes. The power density distribution is relatively uniform on each plane far from the laser focus. There are two defocusing methods: positive defocusing and negative defocusing. When the focal plane is above the workpiece, it is positive defocusing, and vice versa. According to the geometrical optics theory, when the distance between the positive and negative defocus planes and the welding plane is equal, the power density on the corresponding planes is almost the same, but the obtained weld pool shapes are actually different. When defocus is negative, a larger penetration can be obtained, which is related to the formation process of molten pool. The experiment shows that the material begins to melt after being heated by laser for 50~200us, forming liquid metal and causing differential vaporization, forming local pressure steam, which is ejected at a very high speed and emits dazzling white light. At the same time, the high concentration steam makes the liquid metal move to the edge of the molten pool, forming a depression in the center of the molten pool. When negative defocusing occurs, the power density inside the material is higher than the surface, which is easy to form stronger melting and vaporization, so that the light energy can be transmitted deeper inside the material. Therefore, in practical application, when the penetration depth is required to be large, negative defocusing is adopted; When welding thin materials, it is recommended to use positive defocus.

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

Especially after the 42-meter seamless welding technology created by Volkswagen 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. This kind of household appliances cherish the progress of science and technology for people, and advanced laser technology can bring great changes to people's lives. With the continuous consolidation of the global brand status of washing machines, its leading role in the industry began to be fully demonstrated. However, with the support of laser welding machine technology, the home appliance industry will have a deeper reform. According to Haier R&D personnel, the manufacturing process of the inner barrel of the automatic washing machine in the market mostly adopts the "snap-in" process, and there will be gaps or unevenness at the seams of the inner barrel, resulting in low strength of the barrel and unnecessary wear and tear on the clothes. In order to further improve the reliability and refinement of the inner barrel, Haier washing machine applies the laser seamless welding technology to the new uniform washing machine based on the automobile and shipbuilding industries, which avoids the cracks and unevenness of the inner barrel, comprehensively improves the reliability of the product and cares for the clothes. Due to the improvement of the strength of the inner barrel, the maximum rotation speed of the uniform power washing machine in the dehydration process is also increased by 25% compared with that of the ordinary automatic washing machine, the dehydration efficiency is greatly improved, the power consumption is less, and time is saved.

In addition, it is reported that the "high power laser welding machine technology" jointly developed by China and Germany shipbuilding industry ensures the safety of ships and further strengthens the hull structure; In the aviation field, laser seamless welding technology is also widely used in the manufacture of aircraft engines. At the same time, the laser seamless welding technology of aluminum alloy fuselage can replace rivets, which can reduce the weight of fuselage by 20%. China high-speed railway also introduced the laser seamless welding technology, which not only improved the safety performance, but also greatly reduced the noise, and brought a quiet and comfortable ride environment to passengers.

With the all-round development of science and technology, the continuous consolidation and application of laser welding machine technology has also led the global household appliance industry into a new era. New technology is not only the upgrading of products, but also the display and application of more technologies.

1.tailoredblandlaserwelding technology has been widely used in foreign automobile manufacturing. According to statistics, in 2000, there were more than 100 laser tailor-welded production lines in the world, with an annual output of 70 million tailor-welded blanks for automobile parts, and it continues to grow at a high speed. Domestic imported models Passat, Buick, Audi, etc. Some structures for cutting blanks are also adopted. In Japan, CO2 laser welding has replaced flash butt welding in steel-making industry for the connection of rolled coils. In the research of ultra-thin plate welding, for example, the foil with the thickness less than 100 micron can't be welded, but the YAG laser welding with special output power waveform has been successful, which shows the broad prospect of laser welding. Japan has also successfully developed YAG laser welding for the maintenance of thin tubes of steam generators in nuclear reactors for the first time in the world, and Su Baorong and others have also developed gear laser welding technology in China.

2. In the field of powder metallurgy, with the continuous development of science and technology, many industries have special requirements for materials, and the materials manufactured by melting and casting can no longer meet the needs. Because of its special properties and manufacturing advantages, powder metallurgy materials are replacing traditional melting and casting materials in some fields, such as automobile, airplane, tool and cutter manufacturing. With the development of powder metallurgy materials, the connection problem between powder metallurgy materials and other parts is increasingly prominent, which limits the application of powder metallurgy materials. In the early 1980s, laser welding entered the field of powder metallurgy materials processing with its unique advantages, which opened up new prospects for the application of powder metallurgy materials. For example, the brazing method commonly used in the connection of powder metallurgy materials is used to weld diamonds. Because of the low bonding strength and wide heat affected zone, the brazing material can not meet the requirements of high temperature and high strength, and it melts away. Laser welding can improve welding strength and high temperature resistance.

3. Automobile Industry In the late 1980s, kilowatt laser was successfully applied to industrial production, and now the 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. European automakers such as Audi, Mercedes-Benz, Volkswagen and Volvo in Sweden took the lead in laser welding the roof, body and side frame as early as 1980s. In 1990s, General Motors, Ford and Chrysler introduced laser welding into automobile manufacturing. Although it started late, it developed rapidly. Italy Fiat used laser welding in the welding and assembly of most steel plate assemblies, and Japan Nissan, Honda and Toyota Motor Corporation all used laser welding and cutting technology in the manufacture of body panels. High-strength steel laser welding components are more and more used in automobile body manufacturing because of their excellent performance. According to the statistics of American metal market, by the end of 2002, the consumption of laser welded steel structures will reach 70,000 t, which is three times higher than that of 1998. According to the characteristics of large batch and high degree of automation in automobile industry, laser welding equipment is developing towards high power and multi-channel. In terms of technology, Sandia National Laboratory and PrattWitney jointly conducted a research on adding powder metal and metal wire in laser welding process. The Institute of Applied Beam Technology in Bremen, Germany has done a lot of research on laser welding of aluminum alloy body frame. It is believed that adding filler to weld helps to eliminate hot cracks, improve welding speed and solve tolerance problems. The developed production line has been put into production in Mercedes-Benz's factory.

4. Electronic Industry Laser welding has been widely used in electronic industry, especially microelectronics industry. Because laser welding has the advantages of small heat affected zone, fast heat concentration and low thermal stress, it shows unique advantages in the packaging of integrated circuits and semiconductor device shells. In the development of vacuum devices, laser welding has also been applied, such as molybdenum focusing electrode and stainless steel support ring, rapid heating cathode filament assembly and so on. The thickness of elastic thin-walled corrugated sheet in sensor or thermostat is 0.05-0. 1mm, which is difficult to solve by traditional welding method. TIG welding has the advantages of easy penetration, poor plasma stability and many influencing factors, so laser welding has a good effect and is widely used.

5. Laser welding of biomedical biological tissues began in 1970s. Klink et al. and jain[ 13] successfully welded fallopian tubes and blood vessels with laser and showed their advantages, which made more researchers try to weld various biological tissues and spread them to other tissues. The research on laser welding nerve at home and abroad mainly focuses on the wavelength and dose of laser, functional recovery and the selection of laser solder. On the basis of laser welding of small blood vessels and skin, Liu also studied the welding of common bile duct of rats. Compared with the traditional suture method, laser welding has the advantages of fast anastomosis speed, no foreign body reaction in the healing process, maintaining the mechanical properties of the welded part, and repairing the tissue to grow according to its original biomechanical properties, so it will be more widely used in biomedicine in the future.

6. Other fields In other industries, laser welding is gradually increasing, especially in China where special materials are welded. For example, laser welding of BT20 titanium alloy, HEl30 alloy, lithium ion battery, etc. GlamacoCoswig, a German glass machinery manufacturer, has developed a new laser welding technology for flat glass in cooperation with IFW Joint Institute of Technology and Materials Experiment.

Fold and edit the benefits of hybrid welding in this section.

Laser composite welding technology has obvious advantages. For laser mixing, the advantages are as follows: greater penetration/greater gap welding ability; The toughness of weld is good, and adding auxiliary materials can affect the lattice structure of weld. There is no sag on the back of the weld when burning through; The scope of application is wider; With the help of laser substitution technology, the investment is less. For laser MIG inert gas shielded welding, the advantages are as follows: higher welding speed; Large welding depth; Generating less welding heat; The strength of the weld is high; Small weld width; The welding bumps are very small. Therefore, the production process of the whole system is stable and the equipment utilization rate is good; The workload of weld preparation and weld treatment after welding is small; The welding production has short working hours, low cost and high production efficiency; It has good optical equipment configuration performance.

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

Development status of folding editing this paragraph

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

At present, Harbin Welding Research Institute is at the forefront of domestic laser welding technology research. In recent years, in addition to further broadening and developing new types and equipment of laser welding, we also actively imitate and learn from the latest developments of foreign research, and constantly seek the breakthrough and development of high-power laser welding technology. The latest research results show that they have successfully solved the welding problem of large-scale components in China, which undoubtedly marks a major breakthrough in the field of laser welding technology in China and lays the foundation for the major application of large-scale projects in the future. In addition, the research on laser welding technology in China is still concentrated in the fields of laser hot wire welding and dissimilar metal welding, which is the latest subject of modern laser welding technology research. However, foreign countries have made breakthroughs in related research fields, especially Germany, which has initially mastered the skills and methods of dissimilar metal welding. In the future, if China really wants to skillfully apply and master laser welding technology and apply it to more fields and industries, it is undoubtedly necessary to break through the above topics and further improve and optimize laser welding technology.

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As a combination of modern technology and traditional technology, laser welding is particularly unique compared with traditional welding technology, and its application fields and application levels are wider, which can greatly improve the efficiency and accuracy of welding. It has high power density and fast energy release, so as to better improve work efficiency, and at the same time, its own focus is smaller, which undoubtedly makes the adhesion between stitched materials better and will not cause material damage and deformation. The emergence of laser welding technology has realized the fields where traditional welding technology can't be applied, and it can simply meet various welding requirements of different materials, metals and nonmetals. Moreover, due to the penetrating power and refraction of laser itself, it can realize random focusing within 360 degrees according to the running track of the speed of light itself, which is undoubtedly unimaginable under the development of traditional welding technology. In addition, laser welding can release a lot of heat in a short time to realize rapid welding, so it has low requirements on the environment and can be carried out at ordinary room temperature without vacuum environment or gas protection. After decades of development, people have the highest understanding and cognition of laser technology, which has gradually expanded from the initial military field to the modern civil field, and the emergence of laser welding technology has further expanded the application scope of laser technology. In the future, laser welding technology can be applied not only to automobile, steel, instrument manufacturing and other fields, but also to military and medical fields, especially medical fields. With its own characteristics of high fever, high integration and hygiene, it can be better applied to clinical diagnosis and treatment of neurology and reproductive medicine. And its own precision advantage will also be applied to more precision instrument manufacturing industries, thus continuously benefiting the development of mankind and society. [ 1]