> Marine aluminum alloy in ship construction
Now it is widely used in ship construction, and the commonly used alloys for marine aluminum plates are 5083 aluminum plate, 5086 aluminum plate, etc. However, there are also many requirements for the selection of marine aluminum alloys.
1. Marine aluminum alloy in ship construction require high specific strength and specific modulus
The yield strength and elastic modulus of the material are the basic parameters for calculating the strength of the ship structure and determining the size of the structure. Since the elastic modulus and density of various aluminum alloys are roughly the same, and adding a small amount of alloying elements or changing the heat treatment state has little effect on them, it is beneficial to increase the yield strength within a certain range to reduce the weight of the ship structure. Generally, aluminum alloys The density is about 2.7~2.8/cm3, and the elastic modulus is about 70~73GPa. However, it is usually difficult for high-strength aluminum alloys to have excellent corrosion resistance and weldability at the same time. Therefore, aluminum alloys with medium strength and corrosion resistance are generally selected for marine aluminum alloys. In addition, cast aluminum alloys also have certain advantages in the field of ships. application.
2. Marine aluminum alloy in ship construction requires excellent welding performance
For ships, welding connection has advantages over riveting connection. Therefore, welding connection method has been widely used in shipbuilding, basically replacing riveting structure. At present, automatic argon arc welding method is mainly used in aluminum ship construction. The good weldability of aluminum alloys means that the tendency of aluminum alloys to form cracks during welding is small, that is, aluminum alloys have good welding crack resistance, and the performance of welded joints does not change much after welding. Because the properties lost due to welding cannot be recovered by re-heat treatment under shipbuilding conditions, this is one of the important characteristics of marine aluminum alloys that are different from other structural aluminum alloys. The strength of AL-Zn-Mg series and AL-Mg-Si series alloys decreases significantly after welding, and the corrosion resistance of AL-Zn-Mg series alloys is also poor after welding, so the two series alloys are limited when used as welding marine materials. . However, AL-Mg alloys do not have this disadvantage. AL-Zn-Mg alloys are mainly used for post-weld heat-treatable components (such as torpedo casings), and AL-Mg-Si alloys are mainly used for profiles.
3. Marine aluminum alloy in ship construction requires excellent corrosion resistance
Ship structures are mostly used in harsh seawater media and marine environments, so whether aluminum alloys are resistant to corrosion is one of the main signs to determine whether they can be used as marine aluminum alloys. It is generally required that marine aluminum alloy substrates and welded joints have no tendency to stress corrosion, exfoliation corrosion and intergranular corrosion in seawater and marine environments; contact corrosion, crevice corrosion and marine organism adhesion corrosion should be avoided as much as possible; small uniform corrosion and spot corrosion are allowed. corrosion.
4. Marine aluminum alloy in ship construction require good cold and hot forming properties
Ships are subjected to cold working (such as hemming, hemming, rolling, stamping, etc.) and hot working (such as hot bending, pyrotechnics, etc.) during the construction process. Therefore, it is required that the marine aluminum alloy is easy to be processed and formed, without cracks and other defects during processing, and can still meet the performance requirements such as strength and corrosion resistance after processing.