Product Code: PIC06_103

Laser Welding with or without Shielding Gas?
Authors:
Mark Faerber, LINDE AG; Hamburg Germany
Presented at PICALO 2006

Customers like to avoid expensive helium based shielding gases and thus laser welding without any gas is increasingly becoming popular. In practice, this means air is used as shielding gas and a mixture of oxygen and nitrogen, respectively. Both gases are effected by laser beam and plasma plume, these are dissociated and ionized and thus activated. Oxygen forms oxides which affect fatigue strength, nitrogen and nitrides affect formability of laser welded material. Degree of activation is influenced by type of laser and related temperature/ density of plasma plume. YAG lasers would therefore accept different shielding gases than CO2 lasers. Another aspect of shielding gas atmosphere at weld pool is supply of the gas. Air is injected if the gas nozzle is misaligned or gas flow too high or too low. The air impurity forms NO which has been measured as an indication of blanketing efficiency.