During high power laser welding partially ionized metal vapor is produced. The plasma over the keyhole absorbs some of the laser power and radiates this energy to the surrounding area. The behavior of positive ions and electrons in the plasma are analyzed and a model is put forward. According to the model a method for removing the plasma by electric-magnetic field is investigated theoretically and experimentally. To increase the magnetic force an external voltage is added between the nozzle and the workpiece. The effect of plasma removing is estimated by elevating the nozzle during welding and measuring the length of deep penetration welding. Experiment results indicate that the efficiency of laser power increases with increasing magnetic field intensity. There is an optimum external voltage to achieve the best driving effect. These results are discussed and analyzed. It is indicated that suitable assisting electric and magnetic fields can reduce the shielding effect of the plasma and increase the efficiency of laser power.

Topics
Leptons, Lasers, Chemical bonding, Partially ionized plasma, Welding
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© 2001 Laser Institute of America.
2001
Laser Institute of America
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