Abstract
During the last decade, the demand for natural gas has steadily increased for the prevention of environmental pollution. For this reason, many liquefied natural gas (LNG) carriers have been manufactured. Since one of the most important issues in the design of LNG carriers is to guarantee structural safety, the use of low-temperature materials is increasing. Among commonly employed low-temperature materials, nickel steel has many benefits such as good strength and outstanding corrosion resistance. Accordingly, nickel steels are one of the most commonly used low-temperature steels for LNG storage tanks. However, the study of fracture toughness with various welding consumables of 7% nickel alloy steel is insufficient for ensuring the structural safety of LNG storage tanks. Therefore, the aim of this study was to evaluate fracture toughness of several different weldments for 7% nickel alloy steels. The weldment of 7% nickel alloy steel was fabricated by tungsten inert gas (TIG), flux cored arc welding (FCAW), and gas metal arc welding (GMAW). In order to assess the material performance of the weldments at low temperature, fracture toughness such as crack tip opening displacement (CTOD) and the absorbed impact energy of weldments were compared with those of 9% nickel steel weldments.
Highlights
The demand for liquefied natural gas (LNG) is constantly increasing for the prevention of environmental pollution
The weldments of ERNiCrMo-3 with flux cored arc welding (FCAW) and gas metal arc welding (GMAW) exhibit a similar tendency in yield and tensile strengths as expected
The mechanical characteristics of 7% nickel alloy steel weldments were evaluated based on tensile, Charpy-V impact, and crack tip opening displacement (CTOD) test results
Summary
The demand for liquefied natural gas (LNG) is constantly increasing for the prevention of environmental pollution. In this trend, various types of LNG carriers have been developed and are operating worldwide. The membrane-type tanks have a very thin primary barrier of Invar alloy or SUS 304L inside the cargo tank. The most common types of membrane-type tank are GTT Mark III and No 96 types. Mark III consists of two layers of R-PUF (reinforced polyurethane foam) separated by triplex in order to configure an insulation system [1]. The No 96 type composes a grillage structure made of plywood and filled with perlite in order to maintain tightness and insulation [2]
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