ステンレス鋼CO_2レーザ溶接時のポロシティ生成機構の解明と低減法

概要

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A large amount of porosity is liable to be formed in high power CO_2 laser welds of stainless steels. The formation mechanisms of porosity have not been satisfactorily understood up to the present. In this study, therefore, microfocused X-ray transmission in-situ observation system was utilized to observe the behavior of a keyhole and the formation situations of bubbles and pores during high power CO_2 laser welding. It was observed that a keyhole fluctuated in geometry unstably and vibrated up and down dynamically, and accordingly many bubbles were frequently generated in the bottom part of a molten pool from the tip of the deep keyhole. Almost all bubbles were captured into spherical pores by solidifying solid-liquid interface during floating up near the bottom part of the weld pool. Moreover, it was revealed that partial penetration welding with a forward inclination of a laser beam or in N_2 shielding gas, and full penetration welding in any shielding gas were beneficial to the reduction and prevention of porosity because the formation of bubbles was suppressed or prevented.
社団法人溶接学会の論文
2001-11-05