Laser welding systems technology is increasingly used in industrial production and plays a vital role, such as in military, medical, aerospace, 3℃ auto parts, mechanical sheet metal, new energy, bathroom hardware and other industries. Laser welding has unique advantages in laser sealing and welding of efficient packaging devices, oxygen sensors, sensors, covers, relays, metal shells, lithium batteries, aluminum covers, shells, aluminum shell batteries, aluminum shell cells, aluminum shells, iron shells, microwave components, microelectronic devices, etc. Here we introduce the causes and solutions of seal subsidence during laser sealing of square aluminum shells.
Causes of laser welding seal subsidence
- The welding power is too high, the welding speed is too low, and the time is too long, causing the weld to collapse.
- The weld gap is too large.
- The welding spatter is too large.
In view of the above reasons, in addition to setting the appropriate welding power and welding speed, Jinmi Laser will introduce you in detail the solutions to the large weld gap and laser spatter.
Solutions to excessive weld gaps
- When welding has high strength requirements, fill the weld with materials of the same material as the parent material.
- When welding strength requirements are not high, use laser wire welding.
- Generally, in order to avoid weld gaps, the welding current should be increased and the surface weld should be covered at the operation site.
Solutions to laser spatter
Spatter is the melted metal that flies out of the weld pool. After the metal material is heated to the melting point, it changes from solid state to liquid state, and continues to heat up and changes to gas state. When the laser pump is continuously heated, the solid metal becomes liquid and forms a pool. Then, the liquid metal in the molten pool is heated again and “boils”. Finally, the material absorbs heat again to vaporize, and boiling causes the internal pressure to change, bringing out the liquid metal on the surrounding surface, and finally producing “splashing”.
1. Change the energy distribution of the laser spot to avoid boiling, and try not to use a Gaussian distribution beam.
Changing a single Gaussian distribution laser beam to a more complex annular + central beam can reduce the high temperature vaporization of the central material and reduce the generation of metal gas.
For method 1, the flying ball is reduced, but there may still be a problem: as the metal vapor is continuously released, a large amount of plasma cloud will be generated at the same time. After the metal vapor is generated, if it is not released in time, it will leave pores on the surface and core of the material after melting, resulting in defects.
2. Change the scanning method, swing welding
The use of the laser head swing method can improve the temperature uniformity of the weld and avoid boiling due to excessive local temperature. As long as the X and Y axes of the motion mechanism are controlled, the swing of various trajectories can be completed.
However, shaking welding can only reduce the flying ball by a small amount. This is because the larger the probe, the greater the improvement of the weld temperature uniformity, but the efficiency of the welding front is reduced, and the welding speed has to be slowed down. However, while the speed is reduced, the lateral feed of the swing is compressed, which is more and more close to the continuous non-swinging state. The heating time of the material becomes longer, boiling and vaporization still exist, and splashing and metal vapor cannot be completely avoided.
3. Use short wavelength to improve absorption rate and use blue light to reduce splashing
Since low absorption wavelength high-power laser cannot cure the soaring, how about changing to short wavelength? The laser absorption rate of traditional metals has a significant downward trend with the increase of wavelength. High reflectivity non-ferrous metals such as copper, gold, and nickel are more obvious.
Summary
Seal sinking is one of the common problems in the laser welding systems process, which directly affects the welding quality and product performance. Through the above strategies, this problem can be effectively solved and the overall efficiency and quality of laser welding can be improved.