Abstract
As a significant laser welding defect, keyhole-induced porosity has detrimental effects on the property of welded joint. In this paper, computational fluid dynamics is used to investigate the porosity suppression during laser welding. A three-dimensional deep-penetration laser welding model considering moving heat resource and keyhole dynamic behavior has been established and verified by a series of CO2 laser welding experiments. The effect of welding parameters on porosity suppression in a 304 stainless steel CO2 laser welding is investigated. Numerical results reveal that the major factor for the suppression of porosity formation is the matching relations between the keyhole self-fluctuation frequency and the keyhole fluctuation frequency. With the pulse frequency of 30 Hz, the porosity formation is significantly prevented. For different duty ratios of laser modulation, 80% of duty ratio has the best effect with the given operating parameters. The best prevention effect appears when the pulse frequency and duty ratio made the keyhole fluctuate closest to its self-fluctuation frequency. The calculated and experimental results also showed that keyhole-induced porosity decreases with increasing welding speed.
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