Product Code: ICAL09_1805

Prevention of Porosity by Oxygen in Partial Penetration Laser and Laser-GMA Hybrid Welding
Susumu Tsukamoto, National Institute for Materials Science; Tsukuba, Ibaraki Japan
Lin Zhao, National Institute for Materials Science; Tsukuba Japan
Goro Arakane, National Institute for Materials Science; Tsukuba Japan
Tomohiro Sugino, Ihi Corp.; Yokohama Japan
Presented at ICALEO 2009

Prevention of the porosity has been attempted in partial penetration laser and laser/arc hybrid welding of heavy section steel plates. Bead on plate welding was carried out on 0.10C-0.30Si-1.33Mn steel (JIS SM490A) using 7 kW fibre laser and pulsed GMA. Laser power modulation with triangular waveform was attempted for various frequencies to prevent the porosity. The peak and base powers are 7 and 3 kW, respectively. Small amount of oxygen addition in the shielding gas was also attempted to prevent the porosity. Stability of the keyhole and porosity formation process was observed during welding using an in-situ X-ray transmission imaging system. Laser power modulation was effective to prevent the porosity in fibre laser welding. However, a lot of porosities were formed in hybrid welding with power modulation, since the welding phenomenon was mainly controlled by the frequency of pulsed GMA in hybrid welding. On the other hand, the porosity was effectively prevented by small amount of oxygen addition to the molten pool both in single laser and hybrid welding. It is attributed to stabilization of the keyhole by oxygen.

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