Commonly fiber laser welding machine protective gas mainly include N2, Ar, He, and their physical and chemical properties are different, and therefore their effects on the weld are also different.
The ionization energy of N2 is moderate, higher than that of Ar and lower than that of He. Under the action of laser, the ionization degree is average. Which can reduce the formation of plasma cloud, and increase the effective utilization rate of laser. Nitrogen can chemically react with aluminum alloy and carbon steel at a certain temperature to produce nitrides, which will increase the brittleness of the weld, reduce the toughness, and will have a greater adverse effect on the mechanical properties of the weld joint. Therefore, we do not recommend to use nitrogen to protect aluminum alloy and carbon steel welds.
The nitride produced by the chemical reaction between nitrogen and stainless steel can increase the strength of the weld joint, which will help improve the mechanical properties of the weld. Therefore, using nitrogen as a protective gas when welding stainless steel.
The ionization energy of Ar is relatively low, and the ionization degree is high under the action of laser, which is not conducive to controlling the formation of plasma cloud, and will have a certain impact on the effective utilization of laser. However, the activity of Ar is very low and it is difficult to chemically interact with common metals. The cost of Ar is not high. In addition, the density of Ar is higher, which is beneficial to sink to the top of the weld pool, and can better protect the weld pool, so we use it as a conventional protective gas.
He has the highest ionization energy, and the ionization degree is very low under the action of laser, which can well control the formation of plasma cloud. Laser can act on metal very well, and He has very low activity and basically does not chemically react with metal. It is a good shielding gas for welding seams, but the cost of He is too high. Generally, mass production products will not use this gas. We generally use it for scientific research or products with very high added value.
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