Laser Weldability of Aluminum Alloys(Physics, Processes, Instruments & Measurements)

概要

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This study was performed with the objective of producing sound laser weld beads in aluminum alloys. CO_2 and YAG laser weldability of aluminum alloys was investigated in terms of penetration and porosity formation. Deeply penetrated welds were easily formed in alloys with a considerable content of Mg, Li or/and Zn in an inert shielding gas, and deep penetration was obtained in any alloy welded with a CO_2 laser beam in a nitrogen shielding gas. Welding phenomena, keyhole behavior, and the formation mechanism and preventive remedies for bubble formation and porosity were examined by observation through high-speed video cameras and the x-ray transmission imaging system. It was especially revealed that many bubbles were chiefly generated from a keyhole tip, resulting in the formation of porosity. Porosity formation tendency was interpreted in terms of keyhole stability, vapor ejection direction and melt flows depending mainly upon the welding speed. It was also found that a melt flow in vacuum was different from that in general welding at low speeds in Ar or He gas, and consequently no porosity formation was attributed to no bubble generation. The size and number of pores could become smaller and be reduced at low welding speeds under the negative pressure achieved by a newly developed tornado nozzle.