Abstract
The International Maritime Organization has recently updated the ship emission standards to reduce atmospheric contamination. One technique for reducing emissions involves using liquefied natural gas (LNG). The tanks used for the transport and storage of LNG must have very low thermal expansion and high cryogenic toughness. For excellent cryogenic properties, high-Mn steel with a complete austenitic structure is used to design these tanks. We aim to determine the optimum welding conditions for performing Laser-MIG (Metal Inert Gas) hybrid welding through the MIG leading and laser following processes. A welding speed of 100 cm/min was used for welding a 15 mm thick high-Mn steel plate. The welding performance was evaluated through mechanical property tests (tensile and yield strength, low-temperature impact, hardness) of the welded joints after performing the experiment. As a result, it was confirmed that the tensile strength was slightly less than 818.4 MPa, and the yield strength was 30% higher than base material. The low-temperature impact values were equal to or greater than 58 J at all locations in the weld zone. The hardness test confirmed that the hardness did not exceed 292 HV. The results of this study indicate that it is possible to use laser-MIG hybrid welding on thick high-Mn steel plates.
Highlights
The International Maritime Organization (IMO) is encouraging the application of ships fueled by liquefied natural gas (LNG) to raise the emission standards for ships, thereby reducing the atmospheric contamination caused by them [1,2,3]
It is necessary to use a metal for the construction of an LNG tank that does not become brittle at cryogenic temperatures
The IMO International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) specifies that 9% nickel steel with a high cryogenic impact toughness secured, stainless steel (e.g., A240-304L), 36% nickel steel (Invar), AL5083-O, and high-Mn steel are limited for use in LNG tank materials [4,5] (Table 1)
Summary
The International Maritime Organization (IMO) is encouraging the application of ships fueled by liquefied natural gas (LNG) to raise the emission standards for ships, thereby reducing the atmospheric contamination caused by them [1,2,3]. Since LNG is transported as a liquid, a cargo hold that can store and transport LNG at cryogenic temperatures of −163 ◦C is required [3]. At such low temperatures, the application of common steel, including SS400, has several constraints due to its brittleness. The IMO International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) specifies that 9% nickel steel with a high cryogenic impact toughness secured, stainless steel (e.g., A240-304L), 36% nickel steel (Invar), AL5083-O, and high-Mn steel are limited for use in LNG tank materials [4,5] (Table 1).
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