Observation of spatter formation mechanisms in high-power fiber laser welding of thick plate

Effects of laser focusing properties on weldability in high-power fiber laser welding of thick high-strength steel plate

“…However, high-power fiber laser welding of a thick metal plate, such as stainless steel, steel, and aluminum alloys, has been performed to investigate the effects on weldability of laser-welding parameters, such as laser power, focus distance, welding speed, shielding gas, and beam spot diameter, and of material parameters, such as gap tolerance, surface preparation, and filler materials. [10][11][12][13][14][15][16][17] For example, Kawahito et al 10 investigated the effects of laser power, power density, and welding speed on the formation of sound welds between thick stainless steel plate by high-power fiber laser welding with spot diameters of 130, 200, 360, and 560 lm. The laser power density had a strong effect on the increase in weld penetration depth as welding speed increased, and sound partially penetrated welds with no weld defects, like underfill, undercut, humps, and porosity, were produced at welding speeds from 75 to 167 mm/s and spot diameters of 360 or 560 lm.…”

Weld appearance prediction with BP neural network improved by genetic algorithm during disk laser welding

“…The molten pools, spatters and plasma can be photographed and observed by special vision systems during the high power laser welding [10]. By analyzing the spectrum of the molten pools and plasma, it is believed that the radiation of a molten pool mainly covered the near infrared band, while the plasma radiation gathered at the ultraviolet band.…”

“…Some researchers employed numerical simulation methods to study the mechanism of the molten pools during laser welding [7][8][9]; these methods are highly depending on the accuracy of the numerical simulation models. Zhang et al [10] presented the dynamic behaviors of spatter formation, and clarified the spatter formation mechanisms in the high-power fiber laser welding of a thick plate at low welding speed with high-speed imaging system, but the phenomena and mechanisms of high speed laser welding were not studied. Recently, Zhang and Gao [11] applied an auxiliary diode laser illuminant to get the visual information of the molten pools morphology, and studied the relation between these visual information and the welding quality with fitting method.…”

Study on the burning loss of magnesium in fiber laser welding of an Al-Mg alloy by optical emission spectroscopy

“…The keyhole is not apt to penetrate through the weld pool. As a result, large amount of the keyhole plasma/plume only erupts from the keyhole entrance on the top surface without escaping from the keyhole outlet at the bottom [21]. Finally, the higher Mg I spectral intensity on the top surface is acquired at lower welding speed.…”

“…Thereby, more material is melted, and a rather large melt pool, even in front of the keyhole is formed accompanying with large swellings of liquids fluctuating around the chimneylike keyhole aperture [20]. Most of the incident laser beam directly irradiates on the top surfaces of the swellings or shelfs around the keyhole aperture without propagating into the material via multiple reflections on the keyhole wall [21]. The keyhole is not apt to penetrate through the weld pool.…”