At present, in industrial manufacturing, copper ranks second in the consumption of non-ferrous metals, second only to aluminum. Copper is widely used in the construction industry, electrical, machinery manufacturing and other industries. Copper has good electrical and thermal conductivity, excellent plasticity, and is easy to process by hot pressing and cold pressing. With the continuous improvement of production demand, the application of copper is gradually expanding.
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 chosen by more and more industries. However, due to the low absorption rate of high-reflection materials for fiber lasers, processing is also more difficult, which also has more requirements for laser light sources.
Prone problems in copper welding:
(1) Difficulty in fusion and variability: Due to the relatively large thermal conductivity of copper, the heat transfer speed during welding is very fast, and the overall heat-affected zone of the weldment is also large, making it difficult to fuse materials together; and due to the linear expansion coefficient of copper When the welding is heated, improper clamping force of the fixture will deform the material.
(2) Pores are prone to occur: Another important problem that occurs during copper welding is porosity, especially when deep penetration welding is more serious. The generation of pores is mainly caused by two situations, one is the diffusion pores directly produced by the hydrogen element dissolved in the copper, and the other is the reaction pores caused by the redox reaction.
Solution:
At room temperature, the absorption rate of copper to infrared laser is about 5%, and the absorption rate can reach about 20% after heating to the vicinity of the melting point. To realize laser deep penetration welding of copper, it is necessary to increase the laser power density.
Using a high-power laser combined with a swing welding head, the laser beam is used 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, with less spatter and fewer micropores after welding.
Soldering skills:
(1) The angle of the welding head is tilted during welding to prevent long-term reflection damage to the laser.
(2) The power of the laser must reach the absorption value of copper to prevent 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) Wobble welding can improve the surface quality of welding.