High power laser technology application in the inddustry of machinery

Application of high power laser processing technology in machinery industry
In the 1970s, two major studies were carried out in the United States: one was the laser welding of body steel plates by the Ford Motor Company; The second is the laser hardening of the surface of the power steering gearbox carried out by General Motors. These two studies have promoted the development of laser processing technology in the machinery manufacturing industry. By the late 1980s, the application of laser processing has increased, of which the most rapid growth is laser cutting, laser welding and laser hardening. These three technologies are now mature and widely used. At the beginning of the 21st century, the "State Key Laboratory of Laser Technology" and the "National Research Center of Laser Processing" set up a laser industrial research group in Wuhan Falilai Cutting System Engineering Co., LTD., and selected key research projects to Falilai Company as a production and research base. Since then, high-power laser processing technology has been able to take root in China's machinery industry.
The reason why laser processing technology has been so widely used is that it has many advantages compared with traditional processing technology: first, non-contact processing, no mechanical force; Second, it can process difficult-to-process materials with high hardness, high melting point and extreme brittleness; Third, the processing precision is high, the thermal deformation is small, and the processing quality is high; Fourthly, combined with modern CNC machine tools, laser processing has the characteristics of high processing precision, good controllability, simple program, saving materials and less pollution. The following is a comprehensive introduction to several laser processing technologies that are widely used in the machinery industry.

1. Laser cutting

Laser cutting is the use of a focused high-power density beam to illuminate the workpiece, the material absorbs the laser energy, the temperature rises sharply, the workpiece surface begins to melt or vaporize, and the active gas is blown into the combustion. With the relative motion of the laser beam and the workpiece, a slit is formed on the workpiece. When the laser illuminates the surface of the workpiece, part of the light is absorbed and the other part of the light is reflected by the workpiece. The absorption part is converted into heat energy, so that the surface temperature of the workpiece rises sharply, the material melts and gasification, resulting in a black hole effect, so that the material absorption rate is improved, and the material in the cutting area is rapidly heated. At this time, blowing oxygen can help fuel, and provide a lot of heat energy, so that the cutting speed is increased; It also blows away the slag to protect and cool the lens.

Laser cutting has many characteristics: laser can cut ultra-hard, ultra-brittle and ultra-soft materials; The slit width is very narrow; The cutting surface is smooth; The cutting surface heat affected layer is shallow and the surface stress is small. Fast cutting speed, small heat affected zone; Suitable for processing sheet metal.

In the manufacturing of industrial machinery, WALC4020 wide-format CNC laser cutting machine jointly developed by "State Key Laboratory of Laser Technology" and Wuhan Farilai (see Figure 1), in addition to meeting the above requirements and the characteristics of wide cutting width, it also has the following technical innovations: Cantilever upside down beam, linear motor drive, SIEMENS 840D controller, proprietary beam quality adjustment system, penetration detection, automatic focusing, drilling and cutting dual flow control system and vertical lift type switching table structure. These technological innovations make the technical performance of WALC4020 laser cutting machine exceed that of other similar products, reaching the highest level.
2. Laser welding

Laser welding is a high speed, non-contact, small deformation of the production and processing method, very suitable for a large number of continuous processing. The laser welding machine produced by Farilai high-power laser research base, or the laser processing equipment integrating welding and cutting, can improve the welding quality exponentially. Its welded joint strength is high, can reach the strength of the base material, equipment performance is stable, good repeatability, high reliability, welded joint without breaking, and in the domestic development of automotive exhaust pipe, transmission parts and production of the workpiece laser welding equipment, can double improve production efficiency and service life, economic benefits are very significant.

3. Laser hardening

Laser hardening is laser hardening, which uses a high-energy laser beam to quickly scan the surface of the cylinder hole, and rapidly absorb energy in a small area (spot size) of an extremely thin layer on the surface, so that the temperature rises sharply (see Figure 2, Figure 3). Due to the excellent heat and thermal conductivity of the metal matrix, the surface heat is quickly transmitted to the other parts of the cylinder matrix, so that the self-cooling quenching is completed in a very short moment to achieve the phase change hardening of the surface of the cylinder hole.

Laser surface hardening compared with the conventional hardening process, its development history is very short, but from the effect has been achieved, laser hardening treatment process is a new surface hardening treatment process with many characteristics.

Its main features are:

(1) High-speed heating and high-speed self-cooling of the material surface.
(2) The surface hardness of the workpiece after laser hardening is high, which is 5% to 20% higher than that of conventional quenching, and a very fine hardened layer can be obtained.
(3) Because the laser heating speed is fast, the heat affected zone is small, and the quenching stress and deformation are small.
(4) Parts with complex shapes and parts that cannot be treated by other conventional methods can be locally hardened. At the same time, different laser hardening treatments can also be performed on different parts of the same part according to needs.
(5) Laser hardening process cycle is short, high production efficiency, the process is easy to achieve computer control, high degree of automation, can be incorporated into the production line.
(6) Laser hardening depends on the conduction of heat from the surface to the inside, without cooling medium, no pollution to the environment.

According to the heat treatment theory, the hardness of materials after heat treatment is closely related to the rate of temperature change. The higher the rate of change, the higher the hardness and the better the wear resistance. After laser quenching, martensite and letensite with fine crystal and dense structure can be obtained on the surface of the workpiece, the surface graphite disappears, the carbide content increases, the dispersion increases, and the residual austenite is produced in the subsurface. For cast iron materials, after the surface hardness of the workpiece is greatly improved, the hardness can be increased from the original 180 ~ 250HV to about 1000HV, the wear resistance is increased by more than 3 to 4 times, and the fatigue resistance and corrosion resistance of the workpiece surface are also significantly improved.

With the successful development of high-power laser, laser processing technology has been rapidly developed and widely used in the machinery industry, high-power laser cutting and welding technology will play a good role in boosting nat