Overview of marine grade aluminium

Marine grade aluminium usually use aluminum magnesium alloy, aluminum magnesium silicon alloy and aluminum zinc magnesium alloy. The most common are aluminum magnesium alloys and aluminum zinc magnesium alloys which are conducive to welding. The strength of aluminum magnesium silicon alloy and aluminum magnesium silicon alloy is significantly lower than that of aluminum magnesium alloy and aluminum zinc magnesium alloy, and the corrosion resistance of aluminum zinc magnesium alloy after welding is also low, which greatly limits the use of these two aluminum alloys. However, aluminum zinc magnesium alloy and aluminum magnesium silicon alloy have good applications in other aspects. Aluminum zinc magnesium alloy can be used for heat treatable parts after welding, while aluminum magnesium silicon alloy is mainly used for profile manufacturing. The working conditions of ships are relatively special. Ship materials often need to have good strength, impact resistance and corrosion resistance. Marine grade aluminium is mainly medium strength aluminum alloy, which not only has corrosion resistance and certain strength, but also has excellent weldability.

According to different parts, marine grade aluminium can be divided into aluminum alloy for hull structure and aluminum alloy for equipment. Aluminum alloys used for hull structure are mainly three kinds of 5083, 5086, 5456 and 6061 marine grade aluminum alloys. Because they are not easy to be corroded by seawater, they are mainly used in shipbuilding. The strength and processability of 7000 series alloy after heat treatment are higher than that of 5000 series alloy. It is mainly used in shipbuilding extrusion structure and deck structure, but its disadvantage is poor stress resistance and corrosion resistance.

Advantages of marine grade aluminium

Aluminum alloy has such characteristics as low specific gravity, elastic modulus, corrosion resistance, weldability, easy processing, non-magnetic and good low temperature characteristics. When applied to ship construction, it mainly has the following advantages:
(1) Because of its low specific gravity, it can reduce the weight of the ship. This can reduce the power of power equipment and ensure speed; Reduce fuel consumption and improve economy and environmental protection; Improve the aspect ratio of the ship, increase the stability and make the ship easier to operate.
(2) Good corrosion resistance, marine grade aluminium matrix and welded joints have no tendency of stress corrosion, peeling corrosion and intergranular corrosion in seawater or marine environment, which can save maintenance cost and prolong service life.
(3) Good processing performance, easy to carry out cutting, punching, cold bending, rolling and other processing operations; It can manufacture large and wide thin-wall profiles and prefabricated parts (such as cabin wall panels), so as to reduce welding quantity, improve assembly production efficiency and reduce labor cost.
(4) The welding performance is good, the welding treatment is simple, and the automatic argon arc welding method is used, which has good forming, few cracks and easy correction. (5) The elastic modulus is 70 ~ 73 GPA, which has greater ability to absorb pulse voltage and higher safety.
(6) Aluminum chips are easy to obtain and can be recycled to improve the utilization rate of materials and reduce the cost of materials.
(7) No low temperature brittleness, suitable for low temperature equipment.
(8) Because the material is non-magnetic, the compass is not affected, and the stealth performance of the ship is also increased.
(9) No pests, dry and wet deformation, no combustion, safer in case of fire.

Specific application of aluminum alloy in shipbuilding and ocean engineering

Deformed aluminum alloy is mainly used for the overall construction of superstructure of ships and marine engineering equipment, 1000 ton all aluminum environmental monitoring ship, scientific research ship, high-speed passenger ship (cruise ship), catamaran or trimaran ship, electric ship, inland water high-speed boat, etc; Cast aluminum alloy is mainly used for deck accessories, pumps, valves and non load-bearing outfitting parts. Marine grade aluminium are mainly aluminum magnesium alloy, aluminum magnesium silicon alloy and aluminum zinc magnesium alloy. 6063 aluminum alloy profiles are commonly used for portholes in ship structures, while 6063 and 6061 aluminum alloy profiles are usually used for masts and ladders. In addition, the wall panel is made of extruded aluminum magnesium alloy, which can prevent deformation during welding and ensure more sufficient stress distribution. Aluminum magnesium alloy is widely used in hull structure, among which marine grade aluminum 5454and 5052 marine grade aluminum  are the main materials for manufacturing deck.

Application of aluminum alloy in offshore helicopter platform. Steel is used as the main building material for offshore oil platforms. Although steel has high strength due to long-term exposure to the marine environment, it also has many problems, such as easy to rust and short service life. Helipads play a very important role in building critical infrastructure for offshore oil and gas resources. It is used for taking off and landing of helicopters and is an important part of contact with the ground. Due to its size, weight requirements and structural stiffness, aluminum helipad module is widely used because of its light weight, good strength and stiffness. The aluminum alloy helicopter platform includes a subframe and a deck unit connected to the subframe and formed by splicing aluminum alloy profiles. A part of the contour is "I" shaped and located between the upper floor and the lower floor. The metal properties and bending strength of aluminum alloy profiles are used to meet performance requirements and reduce self weight. In addition, the aluminum alloy helicopter platform is easy to maintain in the marine environment and has good corrosion resistance. Using it in the welding area can prolong the service life and avoid damage.



Application of aluminum alloy in civil ship field. The use of aluminum alloy in shipbuilding can be traced back to the end of the 19th century and was first used in Europe and America. However, almost no aluminum alloy can meet the strength and corrosion resistance of industry standards, and has not been widely used. Therefore, aluminum alloy is not mainly used in the field of civil ships. However, with the rapid development of modern metallurgical industry, shipbuilding industry began to pay attention to corrosion-resistant aluminum magnesium alloy. In the middle of the 20th century, the related aluminum alloy technology also achieved some success, and the use of aluminum alloy in civil ships reached the peak, such as the development of aluminum alloy plate (5486-h35456-h3). The number of applications of sxxx5054 series alloys (made in the UK), the birth of TIG aluminum welding technology, etc. In the middle and late 20th century, with the development of welding technology, the price of aluminum and aluminum alloy decreased. The higher market demand for aluminum and aluminum alloys has led to the development of aluminum and aluminum alloys and the application of new aluminum alloys in the field of civil ships.

Application in LNG (liquefied natural gas) cargo ship. With the continuous development of offshore oil and natural gas resources, the largest natural gas supply and demand areas in the world are far away and often separated by the ocean. Therefore, modern LNG transportation is mainly based on maritime transportation. Building LNG storage tanks at sea requires metals with good low temperature characteristics, certain strength and toughness. The strength of aluminum alloy material at low temperature is higher than that at room temperature, and aluminum alloy is lighter and more corrosion-resistant in marine atmosphere, making it an ideal choice for use in low-temperature marine environment. A large amount of 5083 aluminum alloy is also used to build LNG containers and LNG storage tanks, especially in Japan (the largest LNG importer). From 1950s to 1960s, many LNG storage tanks and transport ships were built, including the main hull. The wall structure is completely composed of aluminum alloy 5083 LNG storage tank. Most aluminum alloys have become important materials for the upper storage tank structure because of their unique lightness and corrosion resistance. At present, only a few companies in the world can produce low-temperature aluminum for LNG fuel ships. The thickness of marine grade aluminum plate 5083  developed in Japan is increased to 160 mm, and it still has good strength and fatigue resistance at low temperature.

Application in military ship field. Ship design follows the concept of light structure. It is generally believed that the design of light ships has great advantages in controlling the ship's speed, operation accuracy and manufacturing cost, which can minimize energy consumption and increase the ship's endurance (for example, see the publicly reported catamaran stealth missile boat, trimaran search and rescue ship, etc.). Aluminum alloy can well meet the lightweight requirements of ships, which is why aluminum alloy is often used in high-speed and high value-added ships.

Application of drill pipe in oil and gas production. In addition to shipbuilding, aluminum alloy is also widely used in oil and gas production drill pipes. For example, in the development of submarine oil resources, aluminum alloy materials are usually used in drilling rig facilities. Because the materials for manufacturing drilling equipment greatly affect the exploitation efficiency of seabed oil resources, it is very impractical to maintain drill pipes in drilling equipment. Therefore, the use of aluminum alloy material to manufacture drill pipe will increase the length of drilling equipment. It has the advantages of long service life, strong impact resistance, light weight and low torque. It can effectively reduce the friction of production process and play an important role in improving drilling and production efficiency. Generally, in the development of submarine oil resources, the advantages of aluminum alloy can be fully utilized to greatly improve the service life and production efficiency of equipment, and its application prospect is immeasurable.