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Laser welding is a technology that uses high-energy-density laser beams as heat sources for material processing. Compared with traditional MIG and TIG welding methods, laser welding is a great change for our welding industry, bringing faster speed and reducing your large cost . Today, we will bring you an in-depth interpretation of the development and application of the laser welding technology.
Depending on how the laser interacts with the material, laser welding can be divided into two main modes: heat conduction welding and Keyhole (or deep penetration) welding.
Thermal conduction welding means that the energy of the laser beam is absorbed through the surface of the material and converted into heat energy, and then transferred to the interior of the material through heat conduction, causing the material to be locally heated to the melting temperature, thereby achieving welding. Suitable for welding materials sensitive to heat input such as precision components and electronic components.
Keyhole (deep penetration) welding means that when the laser power density reaches a certain value, the surface of the material will instantly evaporate to form steam, and a small hole filled with steam will be generated under the action of the laser beam. The existence of this small hole allows the laser beam to penetrate deep into the material to form a deep and narrow weld. As the material melts and cools, a strong welded joint eventually forms. It is widely used in automotive manufacturing, aerospace and other fields, especially in applications requiring high-strength, deep-penetration welding.
Most of our fiber laser welding machines uses heat conduction welding method.
Laser welding technology has developed alongside the advancement of laser technology. In recent years, new light sources such as blue laser, green laser, and femtosecond laser, as well as new processes like swing welding, ARM (adjustable ringmode) welding and adjustable spot welding have been continuously introduced. These innovations have solved some welding challenges innovatively , which lead to the rapid promotion and development of laser welding technlogy across various fields of industrial production.
In the past, it is hard for welding metals such as gold, silver, copper, aluminum, carbon steel and so on because of below reasons:
1.High reflectivity and high thermal conductivity of the material requires large initial laser power.
2.During the welding, the large power laser is senstive to the changes of the material surfaces, and result in poor formation of the weld spots or seams.
3.The fast laser welding speed can cause internal defects like porosity, especially in aluminum and aluminum alloys.
But now, all above issues are perfectly overcomed because of the new laser welding technology.
Copper has excellent electrical and thermal conductivity, so it is widely used in the electronic products and electric vehicles manufacturing, particularly in motors, batteries, sensors, and wiring harnesses and terminals.
In the past, we applied infrared lasers for welding metal materials including copper, but copper has a very high thermal conductivity—almost five times that of pure iron and 1.7 times that of pure aluminum. So using infared laser for welding copper and it would bring low absorption, welding spatter, molten metal splashes, porosity, and significant fluctuations in penetration depth.
Therefore, with the emergence of high-power short-wavelength lasers, visible light laser welding and hybrid welding have become ideal processing methods for highly reflective materials like copper and copper alloys as below:
Green laser light has a wavelength of 500 to 560 nm, and copper has an absorption rate of up to 40% for green light at a wavelength of 515 nm, which is about eight times higher than the absorption rate for infrared light around 1 μm. Additionally, it offers higher energy coupling efficiency and reduced sensitivity to surface oxidation.
What’s more, using green laser light can significantly lower the threshold power for deep fusion welding of copper, resulting in less molten spatter and fewer splashes on the weld surface, which are almost unaffected by welding speed. By increasing beam scanning, beam defocusing, and properly modulating laser power, the welding quality can be greatly improved, leading to a substantial reduction in weld defects, as well as a more regular and uniform weld surface.
Blue laser light has a wavelength of 400 to 500 nm, and semiconductor lasers based on gallium nitride can directly produce laser light at a wavelength of 450 nm without requiring further frequency doubling. This technology has advantages such as simple structure, ease of use, high electro-optical conversion efficiency, and high absorption rate.
Compared to commonly used fiber lasers in industrial processing, the absorption rate of metal materials at 450 nm with blue lasers increases by 10% to 60%, particularly for highly reflective metals like copper and gold. It has been verified that the energy consumption required for welding copper is 84% lower than that of infrared lasers. This means that when an infrared laser requires 10 kW of laser power to weld copper, a blue laser only needs about 1 kW or 0.5 kW of power.
By employing an infrared-visible dual-beam hybrid welding process, a lower-power visible laser can enable the infrared laser to achieve forced deep fusion welding of copper below the threshold power for deep fusion welding. This approach significantly reduces welding spatter, has lower equipment costs, and results in high welding quality, making it a method with outstanding advantages and promising application prospects.
When using conventional single-focus laser beams to weld aluminum alloys, porosity is a common defect. The main reasons for the formation of pores in aluminum alloys are:
Currently, laser beam oscillation welding is mainly achieved through galvanometers capable of withstanding high-power lasers. The increased area of the laser beam in oscillation welding enlarges the keyhole and weld pool area, enhancing the stability of the keyhole and weld pool, which significantly improves issues like poor fusion and undercut defects. Additionally, the oscillating beam stirs the weld pool and accelerates convection, increasing the escape speed of bubbles within the weld pool and reducing the porosity rate.
In vehicle production, laser welding technology is mainly used in processes such as laser stitch welding of thick steel plates, laser assembly welding of vehicle assemblies and subassemblies, and laser welding of vehicle parts. All the famous
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