5 series aluminium alloys are non-heat-treatable aluminum alloys. They are widely used in transportation fields such as automobiles and ships because of their light weight, high strength and good corrosion resistance. In recent years, with the development of the marine industry and the increase in the speed of ships, people have put forward new requirements for the performance of marine grade aluminum sheets and extrusions.
Large -size 5 series aluminum panel are mainly used. The current conventional size of aluminum sheets for shipbuilding is 2000mm in width and 6000/8000/9000 mm in length. The aluminium panel thickness is 3-50mm.
Magnesium is the main alloying element of 5xxx aluminum alloys. The solubility of Mg is closely related to temperature. At room temperature, the solubility of Mg in aluminum is only about 1%. The excess Mg element precipitates from the grain boundary as Al3Mg2 phase, thereby reducing the plasticity and corrosion resistance of the alloy. Therefore, it is necessary to control the Mg element content or adjust the process to avoid the precipitation of continuous Al3Mg2 phase at the grain boundary.
The mechanical properties of 5xxx aluminum alloys are tensile strength between 275 and 440 MPa, which is a typical medium-strength aluminum alloy. 5xxx aluminum alloys cannot be improved by solution treatment and aging process, and are not heat-treated strengthened alloys. Therefore, they are basically used in work hardening (H) and annealing (O) states.
After adding a trace amount of Mn element to Al-Mg alloy, the solid solution effect is increased by two times. In addition, adding Mn element can ensure the deformation strengthening effect of the alloy and improve the mechanical properties. At the same time, Mn element can prevent Al3Mg2 phase from precipitating along the grain boundary and improve the comprehensive mechanical properties of the alloy. Therefore, it is very necessary to add Mn element to 5xxx aluminum alloy.
Hot rolling is one of the necessary processing technologies for the preparation of 5 series aluminium alloy plates. Hot rolling requires the control of parameters such as the rolling start temperature, reduction, and rolling speed. The characteristics of hot rolling are low energy consumption, low deformation resistance, good plastic processing, and easy forming. Hot rolling is applied to large ingots, with large reduction, high production efficiency, and is easy to mass produce.