Abstract
The effect of various high-power laser-welding parameters on obtaining deep penetration welds without weld defects has been investigated. However, there are no studies on the effect of laser focusing. In this study, high-power fiber laser welding of a 12-mm-thick high-strength steel plate was performed by using two optics systems with different power density distributions and focus depths (2 or 4 mm) to investigate the effects of laser focusing properties on weldability. Full penetration welds without weld defects were obtained with the 4 mm focus depth optics system at low welding speeds of 25–50 mm/s. High-speed video and X-ray transmission images showed that the behavior of the molten pool on the top surface during laser welding was more stable for the 4 mm system than for the 2 mm system. The keyhole was stable with no large fluctuations, and no bubbles were formed in the keyhole. This result was attributed to keeping the power density within 50–120 kW/mm2 to maintain a stable keyhole shape during the welding. Consequently, it was concluded that the laser-focusing properties during laser welding of a thick steel plate affected the weldability strongly, and the optics system with long focus depth was particularly useful in producing sound welds.
Highlights
In this work, high-power fiber laser welding of a 12-mmthick high-strength steel plate was performed with two optics systems with different focusing properties to investigate1938-1387/2017/29(1)/012003/8/$28.00VC 2016 Laser Institute of AmericaJ
High-speed video and X-ray transmission images showed that the behavior of the molten pool on the top surface during laser welding was more stable for the 4 mm system than for the 2 mm system
High-power fiber laser welding experiments for a 12mm-thick high-strength steel plate were conducted with optics systems A and B
Summary
High-power fiber laser welding of a 12-mmthick high-strength steel plate was performed with two optics systems with different focusing properties to investigate. J. Laser Appl., Vol 29, No 1, February 2017 weldability and behavior of the molten pool and keyhole during laser welding. The effects of laser focusing properties on weld defects, such as underfill, humps, spatter, and porosity, and on penetration depth were investigated. To clarify the welding phenomena arising during high-power fiber laser welding of a thick steel plate, the dynamics of melt flows in the molten pool on the top surface of the specimen and the keyhole behavior affecting porosity formation during the welding were analyzed by using a high-speed video camera and an in situ microfocused X-ray transmission system, respectively
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