Date：2021-10-18 Categories：Industry news Hits：129
Shielding gases are necessary for all laser welding equipment. During the welding process, protective gas spray to the metal that is ready to be welded. So, do you know why we must use shielding gases during laser welding? And which gases can be used as shielding gases? The answers will be showed in the following content.
The function of shielding gases:
1. Protecting focus lens of the laser welders from being contaminated.
The shielding gas can protect the focus lens of the laser welding machine from metal vapor pollution and the sputtering of liquid droplets. In high-power laser welding process, the ejection is very powerful, so it is more necessary to protect the lens under such situation.
2. Dissipating plasma produced by high-power laser welding.
The metal vapor absorbs the power of the laser beam and ionizes into a plasma cloud, and the gas surrounding the metal vapor is also ionized by heating. If there is too much plasma, the laser beam is consumed by the plasma to some extent. Plasma exists on the working surface as the second kind of energy, which makes the penetration depth become shallower and also makes the surface of the weld pool wider. Increase the electron recombination rate by increasing the three-body collision of electrons with ions and neutral atoms to reduce the electron density in the plasma. The lighter the neutral atom, the higher the collision frequency, and the higher the recombination rate. On the other hand, only the shielding gas with high ionization energy will not increase the electron density due to the ionization of the gas itself.
3. Protecting the metal workpiece from oxidation during the welding process.
What are the shielding gases for laser welding machines?
Helium gas is not easy to ionize (high ionization energy), which allows the laser to pass smoothly, and the beam energy reaches the surface of the workpiece without hindrance. This is the most effective shielding gas used in laser welding, but it is more expensive.
Argon gas is cheaper and denser, so the protection effect is better. However, it is susceptible to high-temperature metal plasma ionization, which shields part of the beam from reaching the workpiece, reduces the effective laser power for welding, and also damages the welding speed and penetration. The surface of the weldment protected by argon is smoother than when protected by helium.
Nitrogen is the cheapest shielding gas, but it is not suitable for welding certain types of stainless steel, mainly due to metallurgical problems, such as absorption, which sometimes creates pores in the overlap area.
Previous：3D LASER MARKING MACHINE