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Effect of laser-beam and hybrid-laser-arc welding parameters and filler metal on microstructure and mechanical properties of thick heat-treated steel X8Ni9+QT640 for cryogenic service

Paper presented at 4th International Conference on Welding and Failure Analysis of Engineering Materials, WAFA 2018, November 19-22, 2018, Aswan, Egypt
: El-Batahgy, A-M.; Gook, S.; Gumenyuk, A.; Rethmeier, M.

Fulltext urn:nbn:de:0011-n-5199060 (968 KByte PDF)
MD5 Fingerprint: 0e77a6f7d89fc3343405041e053b9cc3
Created on: 30.11.2018

2018, 10 pp.
International Conference on Welding and Failure Analysis of Engineering Materials (WAFA) <4, 2018, Aswan>
Deutsche Forschungsgemeinschaft DFG
01DH14012; LoWELL
Laserstrahl- und Laserhybridschweißen von vergüteten 9% Ni Stählen für Konstruktion von LNG-Anlagen aus sauberen Energiequellen
Conference Paper, Electronic Publication
Fraunhofer IPK ()
cryogenic steel; laser beam welding; hybrid laser arc welding; microstructure; toughness; hardness; tensile strength

The present research work encloses results of experimental investigations of the interaction between welding process parameters for laser-beam and hybrid-laser-arc as well as type of the filler metal and the achievable mechanical properties of the weld joints on steel grade X8Ni9+QT640 for cryogenic service containing 9% nickel. The results obtained contribute to the development and conversion in the industrial practice a new laser beam-based welding technology for the automated manufacturing of facilities for the liquefaction, storage and the transport of natural gases (LNG facilities). The results show, that the martensitic microstructure of the laser weld metal including low amount of retained austenite not exceeding 3.5% leads to the relatively low V-notch impact energy. The remarkable heterogeneity in the chemical composition of the weld metal through the weld thickness could be recognized in the case of hybrid-laser-arc welding with ERNiCrMo-3 austenitic filler metal, what also led to insufficient impact toughness of the weld metall. The most promising results could be achieved by using 11%Ni filler wire, which is similar to the base metal and provides a homogeneous microstructure with uniform distribution of Ni through the weld seam. It is remarkable, that a correlation between Charpy impact toughness and wire feeding speed and respectively process heat input exists. The highest toughness values were 134±58 J at -196 °C. The both laser as well as laser-hybrid welds passed the tensile test. The failure stress of 720±3 MPa with a fracture location in the base material was achieved for all samples tested.