China State Shipbuilding Group will build 18 271,000 cubic meter very large LNG (liquefied natural gas) carriers for Qatar Energy, a signing ceremony was held in Beijing on April 29, setting a record for the world's largest single shipbuilding order.
Liquefied natural gas (LNG) carriers, as a special type of ship dedicated to LNG transport, have a cargo hold design that must be able to withstand the extreme conditions of LNG at minus 163 degrees Celsius, which makes the manufacturing requirements of such vessels extremely stringent. Therefore, LNG carriers, together with luxury cruise ships and aircraft carriers, are known as the "crown pearl" in the shipbuilding industry, symbolizing the highest level of shipbuilding technology.
Application of aluminum alloy in LNG carrier
The distribution of oil and gas resources in China is more concentrated, but the people who need natural gas are distributed all over the country, and even need to be shipped overseas, which requires the storage tank for liquefied natural gas to have low temperature and good corrosion resistance. Nowadays, LNG cargo ships are the main means of transporting natural gas in our country. In the design of LNG tanker storage tank, it is necessary to ensure that liquefied natural gas does not leak, ignite, and corrosion storage tank, and aluminum alloy is not only a low-temperature metal, but also has good strength and toughness, but also has light weight, easy to carry, corrosion resistance and other characteristics, so that it also has a high application value in LNG cargo ships.
There are about four or five big cans on each ship. Each tank has a volume of more than 30,000 m3 and is either spherical or square. This LNG storage tank is generally made of 6000 pieces of "watermelon skin" type aluminum plate welded, its thinnest point is about 30mm, the "equator" plate thickness is about 170mm, the diameter of the spherical tank is about 41m, the mass is about 900t. The amount of aluminum in such a single tank is mostly higher than 400t.
In addition, the transportation of liquefied chemical gas must also have a loading base and unloading base. Taking the LNG loading and unloading base as an example, the aluminum consumption of the above-ground storage tank is about 1300t/ tank, and the aluminum consumption of the underground type is about 120t/ tank. The aluminum and workpieces used are plates, profiles, castings, forgings, pipes and so on.
Application of aluminum alloy in Marine engineering
Ship aluminum alloy to aluminum-magnesium alloy, aluminum-magnesium-silicon alloy and aluminum-zinc-magnesium alloy based, according to the location used, divided into upper outfitting aluminum alloy, aluminum alloy hull structure, including the perch including mast, porthole, chimney, steering room, hull structure including next door, rib, keel, bottom plate and ship side and so on. The commonly used aluminum alloy profiles for portholes in the superstructure of ships are 6063 aluminum alloy profiles, and 6063 and 6061 aluminum alloy profiles are often used for masts and gangways. In addition, the wall panels use extruded aluminum-magnesium alloy, which can prevent deformation during welding and ensure a more reasonable stress distribution. Aluminum-magnesium alloys have a high application rate in hull structure, among which 5454 and 5052 aluminum alloys are the main materials for deck manufacturing.
The advantages of aluminum alloy used in ships
1. Excellent welding performance. Welding has more obvious advantages than riveting, because in shipbuilding can not be restored by re-heat treatment method due to the loss of performance due to welding, and aluminum alloy has good welding crack resistance, and the performance of welded joints after welding is not much different, so it is very conducive to shipbuilding and welding.
2. Excellent corrosion resistance. When aluminum comes into contact with air, it forms a dense, strong alumina film on its surface, which can resist the erosion of various elements in seawater. Coupled with anodizing technology, aluminum alloys can maintain a very stable form in seawater.
3. Low density and light. The density of aluminum is only one third of that of iron, and under the premise of the same size of the ship, the aluminum alloy ship will bring lighter mass, greatly conducive to the maximum speed of the ship and fuel economy, so as to obtain longer mileage under the same amount of oil.
