Abstract
For keyhole laser welding of tempered steel, we show that the characteristic formation of eddies in the melt flow significantly depends on the focal position. The local melt flow velocities and accelerations were analyzed in-situ by means of x-ray imaging. It was observed that the keyhole geometry as well as the direction of rotation of the eddy close to the weld pool surface changes when the focal-position is shifted by one Rayleigh length.
Highlights
IntroductionDuring continuous-wave keyhole-mode laser welding, the dynamic behavior and the geometric stability of the keyhole strongly contribute to the momentum balance of the 3D-melt flow and the shape of the melt pool. The impact of the laser power on the weld pool geometry was, e.g., reported in Ref. 2 based on in-situ x-ray imaging for CO2 laser welding of aluminum.The corresponding melt flow—visualized by the movement of tungsten carbide particles in the x-ray images— which determines the weld pool geometry and influences the formation of melt ejections and spatters is known to strongly depend on the feedrate and was occasionally reckoned to be influenced by the focal position. For laser welding of titanium, aluminum, and stainless steel, x-ray observations further confirmed that the movement of bubbles and tracer particles in the weld pool are identical and that pore formation decreases with increased welding speed.A reduction of hot cracks in dependence of the melt flow behavior and the weld pool geometry influenced by the focal position was provided in Ref. 7
For keyhole laser welding of tempered steel, we show that the characteristic formation of eddies in the melt flow significantly depends on the focal position
For experiments performed with the focal position of FP 1⁄4 À2:1 mm, this procedure is illustrated in Fig. 3, showing the superposition of 29 particle trajectories, and in Fig. 4(b), showing the corresponding distribution of the average melt flow velocities
Summary
During continuous-wave keyhole-mode laser welding, the dynamic behavior and the geometric stability of the keyhole strongly contribute to the momentum balance of the 3D-melt flow and the shape of the melt pool. The impact of the laser power on the weld pool geometry was, e.g., reported in Ref. 2 based on in-situ x-ray imaging for CO2 laser welding of aluminum.The corresponding melt flow—visualized by the movement of tungsten carbide particles in the x-ray images— which determines the weld pool geometry and influences the formation of melt ejections and spatters is known to strongly depend on the feedrate and was occasionally reckoned to be influenced by the focal position. For laser welding of titanium, aluminum, and stainless steel, x-ray observations further confirmed that the movement of bubbles and tracer particles in the weld pool are identical and that pore formation decreases with increased welding speed.A reduction of hot cracks in dependence of the melt flow behavior and the weld pool geometry influenced by the focal position was provided in Ref. 7. During continuous-wave keyhole-mode laser welding, the dynamic behavior and the geometric stability of the keyhole strongly contribute to the momentum balance of the 3D-melt flow and the shape of the melt pool.. The corresponding melt flow—visualized by the movement of tungsten carbide particles in the x-ray images— which determines the weld pool geometry and influences the formation of melt ejections and spatters is known to strongly depend on the feedrate and was occasionally reckoned to be influenced by the focal position.. For laser welding of titanium, aluminum, and stainless steel, x-ray observations further confirmed that the movement of bubbles and tracer particles in the weld pool are identical and that pore formation decreases with increased welding speed. A reduction of hot cracks in dependence of the melt flow behavior and the weld pool geometry influenced by the focal position was provided in Ref. 7. By evaluating longitudinal cross sections of overlap joints, it was shown that varying the focal positions has a significant influence on the cumulated length of the hot cracks in the weld seams and on the sheet material mixing of dissimilar steel grades
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
