Abstract
The International Maritime Organization (IMO) has developed stricter regulations on emission standards for sulfur oxides, etc., and the demand for Liquefied Natural Gas (LNG) is increasing as an alternative to satisfy these standards. This study relates to fiber laser welding, an approach which offers high-speed welding and low welding deformation for ASTM F1684, which has a low coefficient of thermal expansion (CTE) even in a cryogenic environment. In this study, through three preliminary experiments using 0.25 mm thick Invar, the conditions required to secure sufficient penetration depth and back bead were identified. Through the cross-sectional observation analysis, the welding conditions without defects were identified and the trend of penetration shape according to increasing welding speed was identified. Following a lap joint laser welding experiment under the secured conditions, the mechanical properties were evaluated through the shear strength test and the heat influence range of a fiber laser was identified through the temperature measurement of a welding part. As a result, it was confirmed that the shear strength of the lap joint laser welding part was 86.8% that of the base metal.
Highlights
A lap joint fiber laser welding experiment was performed on ASTM F1684 with a thickness of 0.25 mm and the optimum welding conditions were derived through three series of preliminary experiments, cross-sectional analyses, and shear strength tests
Nine tensile strength tests were performed and the results were compared to the strength of the welding part
ASTM F1684 to identify welding conditions that can lead to excellent welding quality and to analyze the maximum temperature during welding
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. To reduce marine environmental pollution, the International Maritime Organization (IMO) has strictly regulated the sulfur content standard for ship fuel oil, reducing it from. 3.5% m/m (Mass by mass) to 0.5% in January 2020 [1]. As typical offshore petroleumbased fuels cannot meet this regulation, the demand for liquefied natural gas (LNG) as an alternative fuel is increasing and the demand for ships that use LNG as fuel is rising as well [2,3]. When LNG is used, the emission of sulfur oxides (SOx) is reduced by
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