Why do we use protective gases for hand-held laser welding machines? It is a new type of welding method, mainly for thin-wall materials, precision parts welding, spot welding, butt welding, overlap welding, sealing welding, etc., high depth ratio, small weld width, small heat-affected zone, small deformation, fast welding speed, smooth weld, beautiful, no processing or simple processing after welding, high-quality weld, no porosity, can be accurately controlled. A small focus point, high positioning accuracy, easy to-achieve automation.
There are three reasons for this.
Reason 1: It can protect the focusing lens from metal vapor pollution and liquid droplets sputtering
The protective gas can protect the laser welding machine focusing lens from metal vapor pollution and liquid droplet sputtering, especially in high-power welding, because its ejecta becomes very powerful, at this time protecting the lens is more necessary.
Reason 2: The protective gas is very effective in dispersing the plasma shielding generated by high-power laser welding
The metal vapor absorbs the laser beam to ionize into a plasma cloud, and the protective gas around the metal vapor is also ionized by heat. If too much plasma is present, the laser beam is to some extent consumed by the plasma. As the second energy, plasma exists on the working surface, which makes the welding depth shallower and the welding pool surface wider.
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 atom, the higher the collision frequency and air-cooled recombination rate. On the other hand, only protective gases with high ionization energy do not increase the electron density due to the ionization of the gas itself.
Reason 3: The protective gas can prevent the workpiece from oxidation during the welding process
The laser welding machine must use a gas for protection, and the program should be set to the first protective gas and then the laser, to prevent the phenomenon of oxidation of the pulse laser during continuous processing. The inert gas can protect the molten pool when some materials welding do not care about surface oxidation, it can not be considered protection, but for most applications, helium, argon, nitrogen, and other gases are often used to protect the workpiece from oxidation during the welding process.
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