Briefly describes the laser welding
Principle: by optical oscillators and in oscillators hole on both ends of the medium between the lens. Medium is motivated to high-energy state, begin to produce the same phase light waves and bounces back and forth between the mirrors on both ends, forms the photoelectric effect series, the light amplifier, and began to emit laser gain enough energy. Laser can also be interpreted as the electrical energy, chemical energy, heat, light or nuclear energy and other raw energy is converted into certain optical frequency (ultraviolet, visible or infrared electromagnetic radiation beam of a device. Transformation form in some solid, liquid or gas medium are easily. When the media are in atoms or molecules form, the effect is almost the same phase and near - laser beam of a single wavelength. Due to the same phase and a single wavelength, Angle of differences are very small, the highly concentrated to provide before welding, cutting and heat treatment, and other functions can be quite a long distance.
Laser welding is mainly using CO2 laser and YAG laser, YAG laser with high average power, after it emerged as optimization of laser welding and laser seam welding equipment. Laser welding and electron beam welding of significant difference between laser radiation does not produce perforated welding way. And, in fact, when the laser pulse energy density up to 10 power 6 W/CM2, will be in the bai welding welding hole is formed on the metal material welding interface, the pore forming conditions are met, and deep penetration can use laser welding.
In aviation industry and many other applications, laser welding can realize the connection of many types of materials, and laser welding usually has the incomparable superiority to many other fusion welding process, especially the laser welding to connect in the aviation and automobile industry difficult to weld sheet metal material, such as aluminum alloy, etc., and the deformation of small components, connectors are of good quality. Laser processing is another attractive applications using laser can achieve local small-scale heating characteristics, the laser of the hot spots to make it very suitable for PCB electronic devices such as welding, laser can be a very small area on the electronics high average temperature, while outside the joint area basic are not affected.
Laser welding belongs to fusion welding, laser beam as energy, impact on the weld joint. A laser beam is guided by planar optical element (such as mirror), then to reflect on components or lens projecting beam on the weld. Is a non-contact welding, laser welding process does not need pressure, but need to use inert gas to prevent oxidation of molten pool, filler metal with occasional use. MIG welding and laser welding can laser composite MIG welding, the large penetration welding, at the same time greatly reduce than MIG welding heat input.
The advantages and disadvantages
(1) welding position need to be very accurate, must be within the scope of the focused laser beam.
(2) the weldment to use clamp fixture, must ensure that the final location of the weldment with the laser aim the impact of the solder joints.
(3) the largest weldable thickness is restricted, far more than 19 mm penetration thickness of artifacts, not suitable for the use of laser welding in production line.
(4) high reflectivity and high thermal conductivity materials such as aluminum, copper and its alloys, weldability will change by laser.
(5) when the energy to the high-energy laser beam welding, the need to use plasma controller will be ionized gas drive around the pool, to ensure that the weld again.
(6) the energy conversion efficiency is too low, usually less than 10%.
(7) bead rapid solidification, porosity and embrittlement may have concerns.
(8) expensive equipment.
application
Laser welding machine technology widely use in cars, ships, planes, high-speed and high precision manufacturing, brought big improvement for the quality of people's lives, especially leading home appliance industry entered the era of seiko.
Especially in the 42 meters of Volkswagen create seamless welding technology, greatly improving the integrity and stability of car body, in addition, Germany and China shipbuilding industry cooperative research and development of "technology" high power laser welding machine, make sure the safety of the ship, to further strengthen the hull structure; In the field of aviation, laser seamless welding technology also has been widely used in aircraft engine manufacturing, at the same time, the aluminum body laser seamless welding technology can replace the rivet, so as to reduce the 20% of body weight; High-speed rail in China also has introduced a seamless laser welding technology, to improve safety performance, at the same time also greatly reduces the noise, quiet and comfortable driving environment for passengers.
With the comprehensive development of science and technology, continuously consolidate and application of laser welding machine, also led the global home appliance industry entered a new era, new technology is not only the upgrading of products, is also more the display and the application of science and technology.
1, manufacturing, application of laser tailor-welded (TailoredBlandLaserWelding) technology has been widely used in the manufacture of foreign cars, according to statistics, in 2000 the world within the scope of cutting more than 100 laser tailor-welded blank plate production lines, annual output of 70 million pieces of car component tailor-welded blank plate, and continues to grow at high speed. The introduction of domestic production models Passat, Buick, Audi also adopted some cutting billet board structure. Japan in CO2 laser welding instead of flash butt welding rolling coil connections in steel industry, in the research of ultra thin plate welding, such as thickness of 100 micron foil, unable to fusion welding, but through a special power output waveform of YAG laser welding are successful, shows the laser welding of broad prospects. Japan also successfully developed for the first time in the world the YAG laser welding thin tube used in nuclear reactor steam generator maintenance, etc., and also deals with in the domestic Su Baorong gear laser welding technology.
2, powder metallurgy fields With the continuous development of science and technology, special requirements for the materials on a variety of industrial technology, metallurgy method is applied to manufacturing materials cannot meet the need. Due to the advantages of powder metallurgy materials with special performance and manufacturing, in some areas, such as cars, planes, tool cutting tool manufacturing is replacing the traditional metallurgy material, with the increasingly development of powder metallurgical materials, it connects to other parts of problems appear increasingly prominent, limit the application of powder metallurgy materials. In the early eighty s, laser welding, with its unique advantage into the field of powder metallurgy materials processing, has opened up new prospects for the application of the powder metallurgy materials, such as using powder metallurgy material connection that is commonly used in welding diamond brazing method, because of the low bonding strength, heat affected zone width in particular can not adapt to high temperature and high strength requirement caused by solder melting loss, using laser welding can improve weld strength and high temperature resistant performance.
3, the automotive industry in the late 1980 s, kilowatt laser applied successfully in industrial production, and now laser welding production line has been massive in car manufacturing industry, as one of the outstanding achievements of car manufacturing. German audi, mercedes-benz, Volkswagen, Sweden Volvo car factory in Europe in the early 1980 s was pioneered in laser welding roof, car body, side box sheet metal welding, such as in the 90 s America gm, ford and Chrysler have phase to the laser welding is introduced into automobile manufacturing, although started late, but development soon. Italy's fiat in most laser welding is adopted in the welding of steel component assembly, Japan's nissan, Honda and Toyota are used in the manufacturing automobile body covering parts of laser welding and cutting process, the identity of the laser welding assembly parts because of its excellent performance becomes more and more used in automobile body manufacturing, according to the American metal market, by the end of 2002, the consumption of laser welded steel structure will be 70000 t 3 times more than in 1998. According to the characteristics of automobile industrial batch big, high degree of automation, laser welding equipment to develop in the direction of high power, the multiplex type. In process in the United States PrattWitney and Sandia national laboratories in laser welding process in the research, adding metal powder and wire beam technology research institute in Germany Bremen applications use laser welding of aluminium alloy body frame carried out extensive research, more than that is added in the weld filler helps eliminate hot crack, improve the welding speed, solve the problem of tolerance, the development of the production line has been in the Mercedes factory production.
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