威廉希尔官方下载Apr 08, 2020
In the process of laser welding machine, protective gas is used. The protective gas is emitted to the surface of the workpiece through the nozzle mouth with a certain pressure, but many people don't know why the protective gas is used. Which gas can be used as the protective gas body of laser welding, and what are their specific functions?
Protective gas of laser welding machine:
1. Helium is not easy to ionize (the ionization energy is high), which can make the laser pass through smoothly, and the beam energy can reach the workpiece surface without any obstruction. This is the most effective protective gas for laser welding, but the price is more expensive.
2. Argon is cheaper and denser, so the protection effect is better. However, it is easy to be ionized by high temperature metal plasma. As a result, it shields part of the beam from the workpiece, reduces the effective laser power of welding, and damages the welding speed and penetration. The surface of weldment protected by argon is smoother than that protected by helium.
3. Nitrogen is the cheapest protective gas, but it is not suitable for some types of stainless steel welding. It is mainly due to metallurgical problems, such as absorption, sometimes producing pores in the overlap area.
Function of protective gas:
Protect the focus lens from metal vapor pollution and liquid droplet sputtering
Protective gas can protect the focus lens of laser welding machine from metal vapor pollution and liquid droplet sputtering, especially in high-power welding, because the ejecta becomes very powerful, at this time, it is more necessary to protect the lens.
Protective gas is very effective for plasma protective produced by high power laser welding
The metal vapor is ionized into plasma cloud by absorbing laser beam, and the protective gas around the metal vapor will also be ionized by heating. If there is too much plasma, the laser beam is consumed by the plasma to some extent. Plasma as the second energy exists on the working surface, which makes the depth of penetration shallower and the weld pool surface wider. The recombination rate of electrons is increased by increasing the collision of electrons with ions and neutral atoms, so as to reduce the electron density in the plasma. The lighter the neutral atom is, the higher the collision frequency is, and the higher the recombination rate is. On the other hand, only the protective