9%Ni 강이 적용된 LNG 연료탱크의 선상가열에 따른 변형특성에 관한 연구

Abstract

Container vessels continue to grow in size, led by global shipowners. Larger ships can be loaded more cargo at a time, reducing the cost of transportation per teu. This eventually leads to economies of scale, in which the production cost per unit decreases with increasing output. Larger ships, however, are cost-intensive, with a significant increase in the use of ship fuel, and large amounts of sulfur oxides are a major source of marine air pollution due to increased bunker C oil usage. Accordingly, in accordance with the 70th Convention of the Marine Environment Protection Committee of the International Maritime Organization, as of January 1, 2020, MARPOL Annex VI Regulation 14.1.3 will be effective. For vessels that do not meet these criteria to reduce SOx emissions and reduce NOx emissions by reducing the content of manned sulfur oxides from 3.5% to less than 0.5%, IACS Member States Entry to the port is denied. The introduction of LNG propulsion ships is the best alternative to meet environmental regulations and can remove 100% of sulfur oxide emissions compared to existing ship fuels. When the engine is in a four-stroke cycle, it can reduce NOx by 90%, reduce particulate matter (PM) by 90%, and reduce carbon dioxide (CO2) by 15%. It is an environmentally friendly fuel that can be greatly reduced. Recently, 9% Nickel-steel is widely used as a fuel to store LNG condensed at low temperatures. This steel has a low brittle ductility transition temperature, and thus has ductility at extremely low temperatures. LNG storage tank, which is made of 9% Nickel-steel, is manufactured by welding, and it is inevitable that the bending work by heat is inevitable after the welding is completed. Locally existing residual stresses caused by this heat can reduce fatigue strength or increase crack propagation. So each shipyard is conducting research on this. Most shipyards focus on minimizing heat through cold forming for 9% Nickel-steel bending. In this study, the characteristics of the material after line heating ( 600℃, 700℃, 800℃, 900℃) of 9% Ni steel used in the manufacture of LNG fuel tank of ship were verified using by mechanical test. In the heating method by line heating, the initial properties of steel are changed by variables such as temperature, time, and speed. The experimental data of line heating presented in this paper confirmed that the initial change of 9% Ni steel could be minimized.