Effect of external constraint on the characteristics and behavior of the plasma plume during high-power CO_2 laser welding

摘要

Laser-induced plasma has been one of the hotspots of high-power CO_2 laser welding for many years. A novel method was proposed to suppress the plasma plume through external constraints, which resulted in more stable welding process and slightly increased penetration depth. Based on high-speed camera and image processing technology, it was demonstrated that the expansion of plasma plume both in height and width was suppressed by a pair of water-cooled copper blocks laid near laser incident point along the direction of seam. Besides its intensity and size, the dynamical behavior of plasma plume under spatial constraint was observed and analyzed by the characteristic parameters. The constraint mechanism and influence of the spacing between the two copper blocks was discussed. Results showed that external constraint was effective to suppress plasma plume, stabilize welding process, and to increase weld penetration for high-power CO_2 laser welding.