Characteristics and application analysis of laser welding

Laser welding is one of the important aspects of laser material processing technology. In the 1970s, it was mainly used for welding thin-walled materials and low-speed welding. The welding process belongs to heat conduction type, that is, the surface heat is heated by laser radiation, and the surface heat is guided to internal diffusion through heat transfer. By controlling the parameters of laser pulse width, energy, peak power and repetition frequency, the workpiece is melted to form a specific molten pool. Because of its unique advantages, it has been successfully used in precision welding of micro and small parts. The emergence of high-power CO2 and YAG laser has opened up a new field of laser welding. Deep penetration welding based on keyhole effect has been widely used in machinery, automobile, steel and other industries.

Compared with other welding technologies

The main advantages of laser welding are as follows

1. High speed, large depth and small deformation.

2. It can weld refractory materials such as titanium and quartz, and can weld dissimilar materials with good effect.

3. Micro welding. It can be used in the assembly and welding of micro and small workpieces in mass automatic production.

4. It can be welded at room temperature or under special conditions, and the welding equipment is simple. For example, when a laser passes through an electromagnetic field, the beam will not shift; Laser welding can be carried out in vacuum, air and some kind of gas environment, and can be carried out through glass or materials transparent to the beam.

5. After laser focusing, the power density is high. When high power devices are welded, the aspect ratio can reach 5:1, and the maximum can reach 10:1.

6. Laser beam is easy to realize beam splitting according to time and space, and can process multiple beams at the same time.

7. It can be used to weld inaccessible parts. It has great flexibility to carry out non-contact long-distance welding. Especially in recent years, optical fiber transmission technology has been used in YAG laser processing technology, which makes laser welding technology more widely promoted and applied.

Application fields of laser welding

1 powder metallurgy

With the continuous development of science and technology, many industrial technologies have special requirements for materials. The materials manufactured by smelting 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.

2. Application in electronic industry

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 shows 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 and so on.

The thickness of elastic thin-walled corrugated sheet in sensor or thermostat is 0.05-0.1mm, which is difficult to be solved by traditional welding method. Because TIG welding is easy to weld through, poor plasma stability and many influencing factors, laser welding is adopted.

3 manufacturing applications

Laser tailor welding technology has been widely used in foreign car manufacturing. According to statistics, there were more than 100 tailor welded blanks production lines worldwide in 2000, with an annual output of 70 million tailor welded blanks for car components, and it 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.

It is the first time in the world that YAG laser welding is successfully used in the maintenance of steam generator tube in nuclear reactor. In China, Su Baorong and others have also carried out the laser welding technology of gear.

4 biomedical field

Laser welding of biological tissue began in the 1970s. Klink et al. And Jain's successful welding of fallopian tubes and blood vessels by laser welding and its advantages make more researchers try to weld various biological tissues and extend to other tissues. At present, the domestic and foreign research on laser welding nerve mainly focuses on the laser wavelength, dose and its effect on functional recovery, as well as the selection of laser solder. On the basis of the basic research on laser welding small blood vessels and skin, Liu Tongjun also studied the welding of rat bile duct.

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. Therefore, laser welding will be widely used in biomedicine in the future.

5 automotive industry applications

In the late 1980s, kilowatt level laser was successfully applied in industrial production, and 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 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 in Italy uses laser welding in most steel plate assembly. Nissan, Honda and Toyota in Japan 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.