Influence of spatial power modulation on pore and crack formation in laser beam welding of aluminum

Abstract

The effect of spatial power modulation (SPM)—also known as wobble—for the welding of aluminum alloys has been investigated in laser beam microwelding. As the superposition of a high frequency circular oscillation movement and a global feed, two new parameters (A—amplitude and f—frequency) are added to the typical process parameters P—power and vw—welding feed rate. Microscopic and metallographic analyses have been used to determine crack appearance and position. With the choice of a sufficient ratio of A, f, and vw, the cooling behavior can be influenced. This also has an impact on the crack formation. Furthermore, the circular movement influences the local speed of the laser beam which in turn can affect the pore formation. The same effect appears on the depth stability as the keyhole formation strongly depends on the speed of the laser beam. The pore formation and weld depth stability have also been analyzed to determine the difference between conventional welding and welding with SPM.

High-Speed X-Ray Investigation of Pore Formation during Full Penetration Laser Beam Welding of AA6016 Aluminum Sheets Contaminated with Lubricants

“…In conclusion, pores formed in the weld pool through the evaporation of the lubricant, which was enclosed in the gap. These findings explained why these pores cannot be avoided by process strategies like high-speed welding or beam oscillation, which are known to impede the formation of process pores [3,15,16,25]. The effective range of these strategies is limited to the stabilization of the capillary; thus, these optimizations do not impede the formation and growth of pores in the weld pool behind the capillary.…”

Seam Formation in Laser Beam Micro-Welding with Spatial Power Modulation

“…The superposed movement leads to a complicated pattern of the beam path, influencing quality and dimensions of the weld seam. Although, this technique has been introduced a couple of years ago it is still a topic of investigation [6,8,9].…”