Welding processes of metals for offshore environment: Underwater welding
Gyasi, Emmanuel Afrane (2019)
Publishers version
Gyasi, Emmanuel Afrane
2019
103
1-60
Lappeenranta-Lahti University of Technology LUT
LUT Scientific and Expertise Publications Tutkimusraportit – Research Reports
School of Energy Systems
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© LUT University
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https://urn.fi/URN:ISBN:978-952-335-433-3
https://urn.fi/URN:ISBN:978-952-335-433-3
Tiivistelmä
Offshore welding is important in the fabrication process of sophisticated offshore structures with a wide range of materials such as steels and alloyed steels to withstand the harsh and corrosive environment during the exploitation of oil and gas offshore. In this literature study, offshore welding was investigated in three perspectives such as welding process environment, applicable materials for offshore environment and suitable modern welding technologies for underwater welding of offshore structures. The first finding shows that on-board welding, dry dock welding and underwater welding are the main forms of welding process environment offshore. The second finding also shows that thermo-mechanical control process (TMCP) steels could be used for constructing pipelines and offshore structure. Moreover, materials such as 22 Cr and 25 Cr duplex and 6 Mo stainless steels, nickel base austenitic alloys and titanium alloys could also be used for offshore structures since they possess excellent weldable properties, high fracture toughness, high strength, and can also fight against the corrosive environment offshore. However, the third finding which pertains to suitable modern welding technologies for underwater welding of offshore structures was justified by examining the defects conventional welding processes such as shielded metal arc welding (SMAW), flux-cored arc welding (FCAW), gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) have posed on offshore structures and the defects modern welding technologies such as friction stir welding (FSW), laser beam welding (LBW) and Hammerhead “wet-spot” welding could pose on offshore structures. It was therefore evident that underwater welding with conventional welding processes produces more weld joint defects as compared to modern welding technologies. The afore-mentioned finding was further justified by examining the weld joints produced by the said modern welding technologies through tensile test, hardness test and fracture toughness test. It was shown that the strength values of the weld joints in FSW, LBW and Hammerhead “wet-spot” welding were similar to the base materials employed as samples in the experimental welding process. This implies that friction stir welding (FSW), laser beam welding (LBW) and Hammerhead “wet-spot” welding produces fewer or defect-free weld joints and exhibit excellent quality welds as compared to conventional welding processes, hence could serve as suitable modern welding technologies for underwater welding of offshore structures.
Lähdeviite
Emmanuel Afrane Gyasi (2019). Welding processes of metals for offshore environment: Underwater welding. Series 103, ISBN 97 8-952-335-433-3, ISSN 2243-3376.