Laser Shielding Gas Argon-Helium Mixture
Argon-helium mixtures suppress plasma when laser welding highly reflective metals, improving coupling. They stabilize the keyhole effect, which improves weld quality.
Physicochemical Mechanism of Action
The argon-helium mixture consists of argon (about 75%) and helium (about 25%). Both gases are highly inert and have low specific thermal conductivity, which makes them stable at high temperatures. The mixture suppresses the plasma that forms during laser welding by absorbing and diffusing the laser beam's energy. This prevents the plasma from directly hitting the workpiece and improves the coupling of the laser radiation into the metal core.
Metallurgical Relevance & Welding Risks
With highly reflective materials like steel or nickel-aluminum alloys, plasma can be strongly reflected, which impairs the coupling of laser radiation and weld quality. Using an argon-helium mixture solves this problem. A missing or insufficient gas mixture can lead to irregular weld profiles, excessive stress build-up and increased hot cracking risk.
Workshop Practice & Instructions
For laser welding of highly reflective metals, an argon-helium mixture in the ratio 75:25 is used. The gas flow should be set so that it directly reaches and stabilizes the laser beam. An optimal flow rate is typically 10-20 liters per minute. Make sure the gas mixture is clean and free of dust particles, as these can impair coupling.