Aluminum alloys can be divided into two categories: one is deformed aluminum alloys, which are used to process semi-finished products such as plates, strips, foils, tubes, rods, shapes, wires, powders and forgings; the other is cast aluminum alloys, which are used to cast various kinds of castings and die-castings. Among them, the former is most widely used in marine engineering. Since aluminum alloy has the characteristics of high specific strength, strong resistance to seawater corrosion, weldable, easy processing and forming, strong recycling, good environmental protection, no low temperature brittleness, no magnetism, no spark when magnetic collision, etc., the application of marine grade 5083 aluminum sheet in marine engineering can effectively reduce the quality of ships, improve stability and increase the speed of navigation. Therefore, currently aluminum alloy has become one of the main structural materials for ships in many countries in the world, and is widely used to build coastal, lakefront and riverfront facilities. Figure 1 shows the aluminum structure of the coastal building. Due to the high corrosion resistance of aluminum, it does not need to be painted and does not need to keep maintenance, and can be used for 30 years. The characteristic that aluminum does not produce sparks when colliding makes it particularly suitable for the manufacture of ship parts and structures in contact with flammable materials and oil, which can greatly reduce the risk of fire.
Currently, aluminum is not used much in shipbuilding, and for the world, the amount used in 2013 was about 1.1% of its total consumption. 2012 domestic consumption of rolled aluminum in Japan was 974.4kt, of which 159.0kt was consumed in transportation (139.0kt in the automotive industry, accounting for 87.42%, and domestic consumption of extruded aluminum was 784.5kt, of which transportation transportation 141.9kt (131.6kt for automotive industry, accounting for 92.94%), the amount of these two kinds of aluminum in transportation accounted for 17.11% of the total consumption, while the amount of the automotive industry accounted for 89.93% of the materials used in transportation, the amount of the aviation industry and marine engineering is less than 10%, Japan is a country with an underdeveloped aerospace industry, so in the transportation with Japan is a country with an underdeveloped aerospace industry, so it is estimated that the amount of aluminum used in transportation and marine engineering will not exceed 5%, and the consumption of aluminum in Japan has long entered a stable stage, and the amount of marine engineering and ships has been hovering around 20kt/a since 2004. In the aluminum used, marine grade 5083 aluminum sheet is the main material, accounting for about 88%, and extruded material is supplementary, but the coastal facilities are mostly used for extruded material.
Chinese ships with aluminum alloy structure is different from Japan, Japan is a large LNG (liquefied natural gas) ship manufacturing country, the ship has four huge with marine grade 5083 aluminum sheet welded LNG tank, the amount of marine grade 5083 aluminum sheet about 4kt / a ship, China built LNG ships with meta-low temperature brittle Fe-Ni-Mn steel, China only some marine grade 5083 aluminum sheet manufacturing small and medium-sized ships, it is estimated that in 2014 China’s shipbuilding industry with of aluminum is less than 230kt, which is less than 1% of the total apparent consumption of aluminum. However, with the acceleration and increase of China’s advancement to an ocean power, the amount of aluminum in ships, naval vessels and marine engineering will have greater growth, but the average annual growth rate will not exceed 7.5% before 2025.
The industrial production of aluminum started from the world’s first aluminum plant – the United States Pittsburgh Metallurgical Company was completed and put into operation in 1988. In 1891, the shipbuilding industry applied the aluminum shipbuilding parts produced by the plant for the first time. After more than 120 years of research and development, the application of aluminum in ships and vessels and in marine engineering is becoming more and more widespread, and has become one of the promising materials in these sectors.
The earliest aluminum alloy used in shipbuilding was Al-Cu system alloy containing Ni, followed by 2000 series alloy, but their corrosion resistance to seawater was not high, which limited their application in shipbuilding industry.
In the 1930s, 6061-T6 alloy was adopted and the hull was constructed by a riveting method. 5xxx series alloy with corrosion resistance could be welded in the 1940s, and TIG (Tungsten Inert Gas) welding technology was adopted in the 1950s, and the application of aluminum alloy in shipbuilding made great progress in this period. H321 alloy plates, 5086-H111 and 5456-H111 alloy extrusion profiles, which eliminated the Al8Mg5 compound mesh film precipitated along the crystal and solved their spalling corrosion and intergranular corrosion problems due to the adoption of H116 and H117 states, which was a significant milestone progress in the development of naval aluminum alloys in the 1960s. Subsequently, due to the need for materials with higher yield strength, 6xxx series alloys were widely used in naval shipbuilding. For a longer period of time, European, American and Japanese countries mainly chose hull aluminum alloys among 5000 series alloys and 6000 series alloys, while the Soviet Union chose 2xxx series alloys more often. The Chinese naval industry mainly followed the Soviet Union before reform and opening up, and more followed European, American and Japanese since 1980, and independent innovation was gradually strengthened after 2010. Since the 1970s, the research on medium-strength weldable 7xxx series alloys has been increasing, and some progress has been made, which has been applied in shipbuilding.
After the 1970s, the rationalization and light weight of naval structure were paid more and more attention, and the superstructure and outfitting parts of large ships used aluminum alloys in large quantities. For this reason, many aluminum alloys and materials for these fields were developed in this period, including special specification extruded profiles, large wide extruded wall plates and castings, etc.