Laser processes are being investigated for welding steel pipe sections, to replace the metal active gas (MAG) welding process currently used. Weld profiles and microstructures from both autogenous high power Nd:YAG laser welds and hybrid Nd:YAG laser/MAG welds have been compared. Reliable mechanical properties of welded structures can be obtained by understanding how to produce favourable microstructures in laser and hybrid welds. Weld rnicrostructure is influenced by both the cooling profile and the weld metal composition. Hence, as part of the microstructural analysis, cooling curves were taken from the molten pool during both laser and hybrid welding. By investigating laser weld microstructures in a number of steels of different compositions, it was shown that the optimal weld microstructure is acicular ferrite, since its small effective grain size results in high strength and toughness. This microstructure could be obtained in laser/arc hybrid welds using the MAG process with metal-cored wire. In this way, pipeline steels that previously gave unacceptable quality autogenous laser welds could be hybrid welded to meet current pipeline welding standards.
Development of Nd:YAG laser and laser/MAG hybrid welding for land pipeline applications
Welding and Cutting ; 3 , 3 ; 186-191
2004
6 Seiten, 10 Bilder, 1 Tabelle, 9 Quellen
Article (Journal)
English
Neodym-YAG-Laser , Laserstrahlschweißen , Metall-Aktivgasschweißen , Hybridtechnik , Pipeline , Mikrostruktur , Abkühlung , mechanische Eigenschaft , Abkühlungskurve , Schmelzbad , Nadelgefüge , Korngröße , Festigkeit , Zähigkeit (Werkstoff) , Temperatur , Wärmeeinflusszone , Laserleistung , Härteprüfung , Charpy-Spitzkerbschlagversuch
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