New laser welding technology: improvement and development
What is a laser? The first laser beam in the world used a flash bulb to stimulate the ruby grain in 1960. Due to the limited thermal capacity of the crystal, only a very short pulse beam was produced and the frequency was very low. Although the peak energy of instantaneous pulse can reach as high as 10^6 watts, it still belongs to low energy output.
Laser technology uses a polarizer to reflect the laser generated beam to focus on the beam of large energy in the focusing device. If the focus is close to the workpiece, the workpiece will melt and evaporate in a few milliseconds. This effect can be used for the appearance of high power CO2 and high power YAG laser in welding process, and the new collar of laser welding is opened up. Domain. The key of laser welding equipment is high-power laser. There are two main categories, one is solid state laser, the other is called Nd:YAG laser. Nd (nd) is a rare earth element, YAG on behalf of yttrium aluminum garnet, crystal structure and similar ruby. The wavelength of the Nd:YAG laser is 1.06 mu m, the main advantage is that the generated beam can be transmitted through the optical fiber, so it can save the complex beam transmission system, suitable for flexible manufacturing system or remote machining, usually used for higher welding precision. The automobile industry usually uses Nd:YAG laser with output power of 3-4 kilowatts. The other is the gas laser, also known as the CO2 laser, the molecular gas is used as the working medium, producing a uniform 10.6 - M infrared laser, which can work continuously and output very high power. The standard laser power is between 2-5 kW.
Compared with other traditional welding technologies, the main advantages of laser welding are:
1. Fast speed, large depth and small deformation.
2, it can be welded at room temperature or under special conditions. The installation of welding equipment is simple. For example, a laser passes through an electromagnetic field, and the beam does not shift; the laser can be welded in a vacuum, air, and a certain gas environment, and can be welded through glass or transparent material.
3, welding refractory materials, such as titanium and quartz, can be applied to welding anisotropic materials.
4, after laser focusing, the power density is high. When high power devices are welded, the aspect ratio can reach 5:1, up to 10:1.
5. Micro welding can be carried out. After laser beam is focused, small spot can be obtained, and it can be precisely positioned. It can be applied to assembly welding of large and small scale automatic production.
6, welding parts that are hard to reach and carrying out non-contact and far distance welding are of great flexibility. In recent years, especially in recent years, the technology of optical fiber transmission in YAG laser processing technology has made laser welding technology more widely promoted and applied.
7, laser beam is easy to realize light splitting in time and space, and can process multiple beams simultaneously and multi station processing, which provides conditions for more precise welding.
However, there are still some limitations in laser welding.
1, the accuracy of welding parts is high, and the location of beams on the workpiece can not be significantly offset. This is due to the small size of the spot and the narrow welding seam after laser focusing, plus filler metal material. If the workpiece assembly accuracy or beam positioning accuracy can not meet the requirements, it is very easy to cause welding defects.
2, the cost of lasers and related systems is relatively high, and the investment is large at one time.
Process parameters of laser welding
(1) power density
Power density is one of the most important parameters in laser processing. With high power density, the surface layer can be heated to boiling point in the microsecond time range, resulting in a large amount of vaporization. Therefore, high power density is favorable for material removal, such as punching, cutting and carving. For low power density, the surface temperature reaches a boiling point and needs a few milliseconds. Before the surface vaporization, the bottom layer reaches melting point and easy to form good fusion welding. Therefore, in conductive laser welding, the power density is in the range of 104~106W/cm2.
(2) laser pulse waveform
Laser pulse waveform is an important problem in laser welding, especially for wafer welding. When the high-intensity laser beam is projected onto the surface of the material, the surface of the metal will be reflected and lost by the laser energy of 60~98%, and the reflectivity will vary with the surface temperature. During the action of a laser pulse, the reflectance of the 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 that is different from material removal and material melting, but also a key parameter to determine the cost and volume of processing equipment.
(4) the effect of defocus on the welding quality
Because the power density of the spot center at the focus of the laser is too high, it is easy to evaporate into holes. The power density distribution is relatively uniform on all planes leaving the laser focus. There are two ways of defocus: positive defocus and negative defocus. The focal plane is located on the top of the workpiece, and the other is negative defocus. According to the geometric optics theory, when the positive and negative plane of the defocus is equal to the welding plane, the power density on the corresponding plane is approximately the same, but the shape of the molten pool is different in fact. When negative defocus is applied, a greater penetration is achieved, which is related to the forming process of molten pool.
Application field of laser welding
Laser welding is widely applied in manufacturing, powder metallurgy, automobile, electronics and other fields.
In particular, Xiaobian collected the development status of laser welding in the automotive industry, and reduced it as follows:
At present, Germany Volkswagen has laser welding on the roof of brands such as AudiA6, GolfA4 and Passat. BMW and General Company are also at the top of the frame.
The GEM Laser is a system designed for the purple day. Welcome to our website.
Laser technology uses a polarizer to reflect the laser generated beam to focus on the beam of large energy in the focusing device. If the focus is close to the workpiece, the workpiece will melt and evaporate in a few milliseconds. This effect can be used for the appearance of high power CO2 and high power YAG laser in welding process, and the new collar of laser welding is opened up. Domain. The key of laser welding equipment is high-power laser. There are two main categories, one is solid state laser, the other is called Nd:YAG laser. Nd (nd) is a rare earth element, YAG on behalf of yttrium aluminum garnet, crystal structure and similar ruby. The wavelength of the Nd:YAG laser is 1.06 mu m, the main advantage is that the generated beam can be transmitted through the optical fiber, so it can save the complex beam transmission system, suitable for flexible manufacturing system or remote machining, usually used for higher welding precision. The automobile industry usually uses Nd:YAG laser with output power of 3-4 kilowatts. The other is the gas laser, also known as the CO2 laser, the molecular gas is used as the working medium, producing a uniform 10.6 - M infrared laser, which can work continuously and output very high power. The standard laser power is between 2-5 kW.
Compared with other traditional welding technologies, the main advantages of laser welding are:
1. Fast speed, large depth and small deformation.
2, it can be welded at room temperature or under special conditions. The installation of welding equipment is simple. For example, a laser passes through an electromagnetic field, and the beam does not shift; the laser can be welded in a vacuum, air, and a certain gas environment, and can be welded through glass or transparent material.
3, welding refractory materials, such as titanium and quartz, can be applied to welding anisotropic materials.
4, after laser focusing, the power density is high. When high power devices are welded, the aspect ratio can reach 5:1, up to 10:1.
5. Micro welding can be carried out. After laser beam is focused, small spot can be obtained, and it can be precisely positioned. It can be applied to assembly welding of large and small scale automatic production.
6, welding parts that are hard to reach and carrying out non-contact and far distance welding are of great flexibility. In recent years, especially in recent years, the technology of optical fiber transmission in YAG laser processing technology has made laser welding technology more widely promoted and applied.
7, laser beam is easy to realize light splitting in time and space, and can process multiple beams simultaneously and multi station processing, which provides conditions for more precise welding.
However, there are still some limitations in laser welding.
1, the accuracy of welding parts is high, and the location of beams on the workpiece can not be significantly offset. This is due to the small size of the spot and the narrow welding seam after laser focusing, plus filler metal material. If the workpiece assembly accuracy or beam positioning accuracy can not meet the requirements, it is very easy to cause welding defects.
2, the cost of lasers and related systems is relatively high, and the investment is large at one time.
Process parameters of laser welding
(1) power density
Power density is one of the most important parameters in laser processing. With high power density, the surface layer can be heated to boiling point in the microsecond time range, resulting in a large amount of vaporization. Therefore, high power density is favorable for material removal, such as punching, cutting and carving. For low power density, the surface temperature reaches a boiling point and needs a few milliseconds. Before the surface vaporization, the bottom layer reaches melting point and easy to form good fusion welding. Therefore, in conductive laser welding, the power density is in the range of 104~106W/cm2.
(2) laser pulse waveform
Laser pulse waveform is an important problem in laser welding, especially for wafer welding. When the high-intensity laser beam is projected onto the surface of the material, the surface of the metal will be reflected and lost by the laser energy of 60~98%, and the reflectivity will vary with the surface temperature. During the action of a laser pulse, the reflectance of the 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 that is different from material removal and material melting, but also a key parameter to determine the cost and volume of processing equipment.
(4) the effect of defocus on the welding quality
Because the power density of the spot center at the focus of the laser is too high, it is easy to evaporate into holes. The power density distribution is relatively uniform on all planes leaving the laser focus. There are two ways of defocus: positive defocus and negative defocus. The focal plane is located on the top of the workpiece, and the other is negative defocus. According to the geometric optics theory, when the positive and negative plane of the defocus is equal to the welding plane, the power density on the corresponding plane is approximately the same, but the shape of the molten pool is different in fact. When negative defocus is applied, a greater penetration is achieved, which is related to the forming process of molten pool.
Application field of laser welding
Laser welding is widely applied in manufacturing, powder metallurgy, automobile, electronics and other fields.
In particular, Xiaobian collected the development status of laser welding in the automotive industry, and reduced it as follows:
At present, Germany Volkswagen has laser welding on the roof of brands such as AudiA6, GolfA4 and Passat. BMW and General Company are also at the top of the frame.
The GEM Laser is a system designed for the purple day. Welcome to our website.
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