Use of schlieren methods to study gas flow in laser technology

Libor Mrňa; Jan Pavelka; Petr Horník; Jozef Hrabovský

doi:10.1117/12.2257212

11 November 2016 Use of schlieren methods to study gas flow in laser technology

Libor Mrňa, Jan Pavelka, Petr Horník, Jozef Hrabovský

Proceedings Volume 10151, Optics and Measurement International Conference 2016; 101510I (2016) https://doi.org/10.1117/12.2257212
Event: Optics and Measurement 2016 International Conference, 2016, Liberec, Czech Republic

Abstract

Laser technologies such as welding and cutting rely on process gases. We suggest to use schlieren imaging to visualize the gas flow during these processes. During the process of laser welding, the shielding gas flows to the welded area to prevent oxidation of the weld pool by surrounding air. The gas also interacts with hot plasma spurting from the key hole induced by the laser beam incident on the molten material. This interaction is quite complicated because hot plasma mixes with the cold shielding gas while the system is moving along the weld. Three shielding gases were used in the presented experiment: Ar, He and N2. Differences in dynamics of the flow are clearly visible on schlieren images. Moreover, high speed recording reveals a structure consisting of hot gas bubbles. We were also able to determine the velocity of the bubbles from the recording. During laser cutting, the process gas flows coaxially with the laser beam from the nozzle to remove the molten material out of the kerf. The gas flow is critical for the quality of the resulting edge of the cut. Schlieren method was used to study gas flow under the nozzle and then under the material being cut. This actually creates another slot nozzle. Due to the very low speed of flow below the material the schleiren method is already at the limit of its sensitivity. Therefore, it is necessary to apply a differential technique to increase the contrast. Distinctive widening of the flow shaped by the kerf was observed.

Citation Download Citation

Libor Mrňa, Jan Pavelka, Petr Horník, and Jozef Hrabovský "Use of schlieren methods to study gas flow in laser technology", Proc. SPIE 10151, Optics and Measurement International Conference 2016, 101510I (11 November 2016); https://doi.org/10.1117/12.2257212

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KEYWORDS

Plasma

Laser cutting

Gas lasers

Laser welding

Visualization

Gases

Laser applications

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