Experimental Study On Quantitative Characterization Of Fiber Laser Welding Metal Vapor

High-power fiber laser has been increasingly widely used in the automotive, ship,aviation manufacturing industry because of its high efficiency, high power, high beamquality, stability, easy to use, maintenance and other advantages. In the field of welding,fiber laser is regarded as one of the most appropriate heat source for large penetrationwelding. In order to ensure high performance, low defect, high reliability and stability ofwelded joint, and ensure welding quality, fiber laser welding mechanism have to becomplete and thorough understanding. Therefore, the study on quantitativecharacterization of fiber laser welding metal vapor is necessary. And research in this paperis helpful to establish and verify transient phase coupling model in the process of laserwelding holes, molten pool, metal vapor.This paper uses high speed camera and laser welding real-time monitoring system togather metal vapor images and ultraviolet emission radiation signal. Trough research andanalysis of metal vapor geometrical characteristics behavior and ultraviolet emissionradiation signal changes under different process conditions, this paper complete the studyof metal vapor quantitative characterization.Through research and analysis of metal vapor image, analysis results show that themorphology of the welding metal vapor in the transient phase is bigger than in themetastable phase. The results show that metal vapor jet angle will be vertical in thebeginning and deflect in the following. The jet angle deflection shows ascending trendalong with the increase of the gas flow and increase of the welding speed. And it has noobvious relations with welding power. The area of the metal vapor overall show graduallyascending trend along with the increase of the laser power and decrease of the weldingspeed. And it has no obvious relations with the gas flow. Metal vapor area will have a peak at welding transient stage, then decrease and cyclical fluctuations.Through research on ultraviolet emission signal analysis, results show that theultraviolet emission signals will also have a peak in welding transient phase, then signalamplitude decrease and cyclical fluctuations. Side gas flow rate do not have obviouseffects on ultraviolet emission radiation signals strength in a suitable range, and it is reallydecide to metal vapor ultraviolet emission radiation signal strength that is welding powerand welding speed. Ultraviolet emission radiation signals strength under certain conditionsis increased with linear energy increases. These is in conformity with the metal vapor areachange, and show that ultraviolet emission signal can be used to characterize the metalvapor.