During underwater laser beam welding (LBW), the welding quality is severely influenced by the shielding condition of the local dry cavity. Laser-induced plasma that strongly shields laser beam will form in underwater LBW if the laser beam directly irradiate to the water. In this paper, the stability of the local dry cavity and the effect of shielding condition on the weld quality during laser welding of type 304 stainless steel (18 % Cr, 11 % Ni, 2 % Mn, 0.07 % C) were investigated. Firstly, welding experiments under various water depths without any way to exclude water from the welding zone were performed. The maximum water depth that deep penetration welding can be performed is about 2 mm, and a local dry cavity is necessary if the water depth exceeds this value. This shielding effect will lead to the impossibility of deep penetration welding in water. So in the welding, a water curtain nozzle was used to form a local dry cavity. The effect of the shielding conditions (water flow rate, gas flow rate and water flow angle) on the stability of the local dry cavity was studied. When the water flow angle is no more than 60 degrees of angle, as the flow angle increases, the parameter range of a stable local dry cavity becomes larger. The welding results under various shielding conditions show the relationship between the shielding condition and the quality of the weld bead. Under good shielding condition sound weld quality without any porosity and surfce defects can be obtained in underwater LBW.
Effect of shielding conditions of local dry cavity on weld quality in underwater Nd:YAG laser welding
Einfluß der Abschirmbedingungen eines lokalen trockenen Hohlraums auf die Schweißnahtqualität beim Unterwasserschweißen mit Neodym-YAG-Lasern
Journal of Materials Processing Technology ; 174 , 1-3 ; 34-41
2006
8 Seiten, 12 Bilder, 1 Tabelle, 12 Quellen
Article (Journal)
English
nichtrostender Stahl , Chrom-Nickel-Stahl , Unterwasserschweißen , Laserstrahlschweißen , Wasserrückhaltung , Abschirmwirkung , Wasservorhang , Schweißwulst , Schweißbedingung , experimentelle Untersuchung , Schweißzone , Düsenströmung , Strömungsgeschwindigkeit , Wasserströmung , Gasströmung , Strömungswinkel , Schweißfehler
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