Abstract: In high-power laser welding, auxiliary blowing of shielding gas is an essential procedure. The shielding gas of the laser welding machine can prevent the metal material from sputtering and contaminate the focusing mirror, and it can also prevent the plasma generated during the welding process from focusing too much, preventing the laser from reaching the surface of the material. So what shielding gas does the laser welding machine use? Let’s find out below.
The role of laser welding machine shielding gas
1. The shielding gas can protect the focusing lens of the laser welding machine from metal vapor pollution and sputtering of liquid droplets, especially in high-power welding, because the ejection becomes very powerful, and it is more necessary to protect the lens at this time.
2. Shielding gas is very effective in dispelling plasma shielding produced by high-power laser welding. The metal vapor absorbs the laser beam and ionizes into a plasma cloud, and the protective gas around the metal vapor is also ionized due to heat. If too much plasma is present, the laser beam is somewhat consumed by the plasma. Plasma exists on the working surface as a second energy, which makes the penetration shallow and the surface of the weld pool widen. The recombination rate of electrons is increased by increasing the three-body collisions of electrons with ions and neutral atoms to reduce the electron density in the plasma. The lighter the neutral atoms, the higher the collision frequency and the higher the recombination rate; on the other hand, only the protective gas with high ionization energy will not increase the electron density due to the ionization of the gas itself.
3. The shielding gas can protect the workpiece from oxidation during the welding process.
What shielding gas is used for laser welding machine
The laser welding process often uses gases such as helium, argon, and nitrogen to protect the molten pool to protect the workpiece from oxidation during the welding process.
1. Helium: the effect is very good, it is not easy to ionize (higher ionization energy), will not affect the laser transmission, allows the laser to pass smoothly, the beam energy can directly reach the surface of the workpiece without hindrance, and has strong oxidation resistance. This is laser welding Compared with the other two, the protective gas is more effective for machine welding, but the price of ammonia gas is generally a bit higher than others.
2. Argon gas: higher density, better protection effect, the surface of the weldment is smoother than helium gas, but it is easily ionized by high-temperature metal plasma, which will shield part of the beam from shooting to the workpiece, reduce the effective power of welding, and affect the welding speed There are barriers to penetration, and the price is cheaper.
3. Ammonia: As the shielding gas, the price is the cheapest, but there are limitations in use, and it is not suitable for all laser welding processes. It is targeted, and it is not suitable for certain types of stainless steel welding, mainly due to metallurgical problems. Such as absorption, sometimes gas particles will be generated in the overlapping area. The cheapest price.