Views: 0 Author: Site Editor Publish Time: 2022-03-30 Origin: Site
At present, in industrial manufacturing, the consumption of non-ferrous metals, copper, ranks second, second only to aluminum. Copper is widely used in construction industry, electrical, machinery manufacturing and other industries. Red copper has good electrical and thermal conductivity, excellent plasticity, and is easy to be processed by hot pressing and cold pressing. With the continuous improvement of production demand, the application of red copper has gradually been expanded.
However, as a highly reflective material, copper has great difficulties in marking, cutting and welding applications, especially laser welding. Welding requires melting of the base material, often resulting in higher or longer-lasting light return than cutting. The absorption rate of copper increases as the wavelength decreases, which means that lasers in the visible band (for example, green lasers with a wavelength of 532 nm) will have significant advantages for copper welding. It is more popular to use green lasers to weld copper abroad. materials, but green lasers are subject to power limitations.
Laser welding has the advantages of high energy density, less molten metal, narrow heat affected zone, high welding quality and high production efficiency. It can effectively improve production efficiency when applied to copper welding, and is gradually selected by more and more industries. However, due to the low absorptivity of high-reflection materials for fiber lasers, the processing difficulty is also greater, which also has more requirements for the laser light source.
(1) Difficulty fusion and variability: due to the relatively large thermal conductivity of red copper, the heat transfer speed during welding is very fast, and the overall heat affected zone of the welded part is also large, so it is difficult to fuse the materials together; When the welding is heated, improper clamping force of the clamp will cause the material to deform.
(2) Pores are prone to occur: Another important problem that occurs when copper is welded is porosity, especially in deep penetration welding. The generation of pores is mainly caused by two situations, one is the diffusive pores directly generated by the dissolution of hydrogen in copper, and the other is the reactive pores caused by the redox reaction.
The absorption rate of red copper to infrared laser at room temperature is about 5%, and the absorption rate can reach about 20% after heating to the vicinity of the melting point. To achieve laser deep penetration welding of copper, it is necessary to increase the laser power density.
A high-power laser is used in conjunction with an oscillating welding head to stir the molten pool and expand the keyhole during deep penetration welding, which is beneficial to gas overflow, making the welding process more stable, less spatter, and less micro-porosity after welding.
(1) The angle of the welding head is inclined during welding to prevent the laser from being damaged by long-term reflection.
(2) The power of the laser must reach the absorption value of copper to prevent the light from being reflected.
(3) The energy density ratio of the small core diameter of the laser can easily reach the absorption value of copper.
(4) Swing welding can improve the surface quality of welding.
Alternatively, copper can be soldered using a blue laser (455nm). Compared with the fiber laser (1064nm), the laser wavelength of 455nm wavelength is shorter, and the absorption rate of copper to the laser increases as the wavelength decreases. Therefore, when welding copper or red copper materials, blue lasers are more suitable than fiber lasers.