Laser welding is a technology that uses a laser beam to melt and join materials. It has the advantages of high energy density, local concentration, and small thermal impact. However, different materials exhibit different weldability during laser welding, which is closely related to many factors. The following are several main factors:
I. Laser Parameters
1. Laser power: If the laser power is too low, the material cannot receive sufficient energy to melt, resulting in incomplete weld formation. Excessive laser power can lead to over-melting, an overly large heat-affected zone, the formation of pores and cracks, and affect the welding quality.
2. Focal diameter: The size of the focal point can control the concentration and dispersion of laser energy, thereby affecting the welding depth and weld quality. The larger the focus, the larger the heat-affected zone, and the shallower the laser weld seam. The smaller the focus, the more concentrated the laser energy, and the deeper the weld seam.
3. Scanning speed: If the scanning speed is too fast, the laser energy cannot be fully focused, resulting in incomplete weld seams. If the scanning speed is too slow, it may cause excessive melting and an overly large heat-affected zone, which will affect the welding quality.
4. Laser beam mode: Different laser beam modes have an impact on the welding effect. For instance, the laser beam in Gaussian mode has a high energy density and good focusing performance, making it suitable for welding small components. Topological mode laser beams are suitable for welding large areas.
Ii. Material Properties
One additional point: The melting point of the material is one of the important factors affecting laser welding. Low laser power is used when the melting point is high, and high laser power is used when the melting point is high. This can achieve a higher welding speed and efficiency.
2. Thermal conductivity: Materials with high thermal conductivity can conduct heat to the surroundings more quickly, thereby reducing the heat-affected zone, minimizing deformation and heat impact. On the contrary, materials with low thermal conductivity will cause heat accumulation during welding, increasing the heat-affected zone.
3. Coefficient of thermal expansion: Different materials have different coefficients of thermal expansion, which can affect dimensional changes and stress generation during the welding process.
4. Material thickness: The thickness of the material affects the penetration depth and thermal distribution of laser energy. Thinner materials are more easily penetrated by lasers, resulting in narrower weld seams, while thicker materials require lasers of higher power.
5. Reflectivity: When welding materials with high reflectivity, additional measures need to be taken, such as using appropriate absorbent coatings or adjusting laser parameters to ensure the absorption and utilization of laser energy.
Iii. Welding Process Control
1. Welding speed: If the welding speed is too fast, it may result in poor weld quality, irregular weld shape, and an increase in welding defects. If the welding speed is too slow, it may cause excessive melting, overheating at the edge of the weld seam, expansion of the heat-affected zone, and lead to problems such as welding deformation and cracks.
2. Welding power adjustment: An appropriate laser power can ensure the formation and stability of the molten pool, but both excessively high and low power may lead to a decline in welding quality.
3. Laser beam position control: It is very important to ensure that the laser beam is accurately positioned within the target area of the welding joint. Incorrect positioning of the laser beam can lead to incomplete welding joints or welding at the wrong position.
4. Protective gas flow rate: The control of the protective gas flow rate is of great significance for reducing oxidation reactions and preventing porosity.
5. Welding process monitoring: Monitoring and real-time feedback during the welding process can help operators promptly identify potential issues and make corresponding adjustments.
Iv. Environmental Conditions
1. Temperature and humidity: Higher ambient temperature may cause the temperature around the material to rise, increase the thermal diffusion effect, expand the heat-affected zone during the laser welding process, and lead to deformation of the surrounding material. A high-humidity environment will increase the oxidation degree in the welding area, reduce the absorption rate of the laser, and make laser welding more difficult.
2. Environmental cleanliness: During the welding process, contaminants such as dust and impurities in the environment can affect the transmission of the laser beam and the quality of the welding. Contaminants can cause the scattering, absorption and reflection of laser energy, affecting the welding results. Therefore, it is very important to keep the welding area clean and tidy.