What is marine grade aluminium?
The working environment of ships requires structural materials to have certain properties such as mechanical strength, fatigue strength, elongation and impact resistance. However, it is usually difficult for high-strength aluminum alloys to have excellent corrosion resistance and weldability at the same time. Therefore,
Marine grade aluminum alloys generally use medium-strength corrosion-resistant weldable aluminum alloys.such as Al-Mg series (5xxx series) and Al-Mg-Si series (6xxx series),they are best for saltwater,Also best for the marine environment。
Type of marine grade aluminum alloys
Marine grade aluminum alloys mainly include Al-Mg series (5xxx series) and Al-Mg-Si series (6xxx series). The main product types are Al-Mg series plates and profiles, and AlMg-Si series profiles.
The AI-Mg series alloy is a non-heat treatment strengthened alloy in which Mg is added to aluminum alone, or Mg and Mn are added at the same time. Alloys such as A5052 and A5083 containing 2.5%~5%Mg, with different Mg content, can have a tensile strength of 20~30kg/m2 (196~294N/mm2) and can be used as welding structural materials
The AI-Mg-Si series alloy is a heat-treatable and strengthened aluminum alloy with Mg2Si as the strengthening phase. The tensile strength increases with the increase of the solution treatment temperature and the full solution of the solute atoms. The T6 state has higher mechanical properties than the T4 state alloy.
Marine grade aluminum alloys for shipbuilding
Marine grade aluminum alloys can be divided into aluminum alloys for hull structure and aluminum alloys for upper outfitting according to their uses. The hull structure includes: ship side, bottom shell, keel, ribs, adjacent walls, etc., outfitting includes: wheelhouse, bulwark, chimney, porthole, mast, etc.
Characteristics, uses, and chemical composition of marine grade aluminum alloys
|
Type |
Alloy |
Temper |
composition（JIS） |
Features |
Application |
Marine grade Aluminum alloy for hull |
5052 |
O
H14
H34 |
Al ：Remainder
Si： ≤0.25
Cu ：≤0.10
Mg：2.2~2.8
Zn：≤0.10
Mn：≤0.10
Cr：0.15～0.35
Fe：≤0.40 |
Medium strength, good corrosion resistance and formability, high fatigue strength |
Superstructure, auxiliary components, boat hull |
|
5083 |
O
H32 |
Al ：Remainder
Si ：≤0.40
Cu：≤0.10
Mg：4.0～4.9
Zn：≤0.25
Mn：0.40～1.0
Ti：≤0.15
Cr：0.05～0.25
Fe：0～ 0.400 |
Typical welding aluminum alloy has the highest strength among non-heat-treated alloys, good weldability, corrosion resistance and low temperature performance |
The main structure of the hull |
|
5086 |
H32
H34 |
Al：Remainder
Si ：≤0.40
Cu：≤0.10
Mg：3.5～4.5
Zn：≤0.25
Mn：0.20～0.7
Ti：≤0.15
Cr：0.05～0.25;
Fe：0～ 0.500 |
The weldability and corrosion resistance are the same as those of 5083, but the strength is slightly lower and the extrudability is improved. |
Main hull structure |
|
5454 |
H32
H34 |
Al：Remainder
Si ：≤0.25
Cu：≤0.10
Mg：2.4～3.0
Zn：≤0.25
Mn：0.50～1.0
Ti：≤0.20
Cr：0.05～0.20
Fe：0.000～ 0.400 |
Strength 22% higher than 5052, good corrosion resistance and weldability, general formability |
Hull structure, pressure vessel, pipeline, etc. |
|
5456 |
O
H321 |
Al：Remainder
Si：≤0.50
Cu：3.8～4.9
Mg:1.2～1.8
Zn：≤0.30
Mn：0.30～0.9
Ti：≤0.15
Ni：≤0.10
Fe： 0.000～ 0.500
Fe Ni：0.000～ 0.500 |
Similar to 5083, but with slightly higher strength and stress corrosion sensitivity |
Hull and deck |
|
6061 |
T4
T6 |
Cu :0.15～0.4
Mn :0.15
Mg :0.8～1.2
Zn :0.25
Cr :0.04～0.35
Ti :0.15
Si :0.4～0.8
Fe :0.7
Al :Remainder |
The corrosion-resistant alloy that can be strengthened by heat treatment has high strength but low weld strength. It is mainly used for screw and riveting structures that are not in contact with seawater. |
Superstructure, partition structure, frame, etc.。 |
Marine grade Aluminum for outfitting |
1050
1200 |
H112O
H12
H24 |
Al ：Remainder
Si： ≤0.25
Fe：0.40
Cu ：≤0.50
Mn：≤0.50
Mg：≤0.50
Zn：≤0.15
Ti ：≤0.03 |
Low strength, good workability, weldability and corrosion resistance, high surface treatment |
Interior decoration |
Cu ：≤0.50
Mn：≤0.50
Zn：≤0.15
Ti ：≤0.03
Fe Si：≤1.0 |
3003
3203 |
H112O
H12 |
Al ：Remainder
Si： ≤0.60
Fe：≤0.70
Cu ：≤0.50
Mn：1.0~1.5
Zn：≤0.10
（3202） |
Strength 10% higher than 1100, good formability, weldability, and corrosion resistance |
Inside, the top and side panels of the LPG tank |
Features of Marine grade aluminum alloys
Marine grade aluminum alloys have characteristics such as low specific gravity, elastic modulus, corrosion resistance, weldability, easy processing, non-magnetic and good low temperature characteristics. When it is 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 the speed; reduce fuel consumption, improve economy and environmental protection; improve the ship’s aspect ratio, increase stability, and make the ship easier to maneuver.
(2) Good corrosion resistance. The marine aluminum alloy substrate and welded joints have no stress corrosion, spalling corrosion and intergranular corrosion tendency in seawater or marine environment, which can save maintenance costs and extend service life.
(3) Good processing performance, easy to perform cutting, punching, cold bending, rolling and other processing operations; large and wide thin-walled profiles and prefabricated parts (such as bulkhead panels) can be manufactured, thereby reducing the amount of welding and improving The production efficiency of final assembly reduces labor costs.
(4) The welding performance is good, the welding process is simple, and the automatic argon arc welding method is used, which has good forming, less cracks and easy correction. (5) The elastic modulus is 70-73 GPa, the ability to absorb pulse voltage is large, and the safety is higher.
(6) Aluminum scraps are easy to obtain and can be recycled, which promotes the improvement of material utilization and reduces the cost of materials.
(7) No low temperature brittleness, suitable for low temperature equipment.
(8) Since 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 burning, safer when on fire.
