セラミックスのレーザ溶接(第 1 報) : ビード形状と溶接欠陥について

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A CO_2 laser was applied for welding Al_2O_3-SiO_2 sintered ceramics with 48-99.5wt% alumina contents. The effects of welding parameters and preheating temperature on the bead shape, penetration depth and weld defects including underfill of the bead, porosity and cracking were discussed. The results obtained are summarized as follows : (1) Paralled-sided and deeply penetrated beads were obtained in mullite ceramics and the penetration depth, which is inversely proportional to the welding speed, was deeper than that of laser welding of SUS304. In high alumina ceramics, a wine-cup bead was resulted from the laser-produced plasma. The differences in welding characteristics between ceramics and metals were discussed on the basis of the welding mechanism. (2) Underfill due to material vaporization is remarkable when the depth-to-width ratio of the bead is one, resulting in around 75% of heat loss, whereas the underfill is sufficiently small when the focal position is on the workpiece surface. (3) Porosities were formed along the fusion boundary in low alumina mullite and in the nail head of the bead in high alumina ceramics. (4) When the preheating temperature is not high enough, there appeared two types of weld-cracks; a transverse crack, which propagates perpendicularly to the bead and a longitudinal crack, which propagates parallelly to the bead from the bottom surface. (5) At high welding speeds, the transeverse crack is prevented at the preheating pemperature T_t, where the materials have plasticity; T_t is 1000℃ in mullite; 1200℃ in 95wt%Al_2O_3; 1400℃ in 99.5wt% Al_2O_3. At low welding speeds, transverse crack can be prevented by widening the heat affected zone at preheating temperatures down to 600℃ in low alumina mullite. The longitudinal crack occurs around critical speeds for full-penetration welding, and can be prevented at preheating temperatures 200℃ higher than T_t.
社団法人溶接学会の論文
1982-02-05

セラミックスのレーザ溶接(第 1 報) : ビード形状と溶接欠陥について

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