5052 aluminum alloy is a typical alloy in the 5xxx series alloys. The Mg content is between 2.2% and 2.8%. It is a low Mg, heat-treated non-strengthable aluminum alloy. It has medium strength, good corrosion resistance, weldability and easy processing and forming, etc. Features. The annealed state of the alloy has good plasticity and high work hardening rate, so the plasticity is low in the hard state. After the hot-rolled sheet, the alloy's recrystallization temperature is about 288°C when the cold working rate is 50%. Mg is the only strengthening element in the alloy, which has a certain solid solution strengthening effect, and increases the work hardening rate of the alloy, and the alloy can obtain more obvious strain strengthening.
5052 alloy is often used as a decorative panel material because of its excellent forming properties, corrosion resistance, weldability, and fatigue strength. With the development of machinery, automobiles and other related industries, the demand for 5052 aluminum alloy sheets is increasing, and its research mainly focuses on alloy welding technology. Now let's take a look at the welding characteristics of aluminum-magnesium alloy 5052 aluminum alloy:
A.Strong reduction ability.
The affinity of aluminum and oxygen is very strong. Aluminum can easily combine with oxidation in the air to form a dense and strong A1203 film with a thickness of about 0.1μm; the melting point of A1203 is as high as 2050℃, which is much higher than the melting point of aluminum and aluminum alloy (500 -600 ℃). During the welding process, the oxide film will hinder the good bonding between the metals and easily cause slag inclusion. The aluminum oxide film also adsorbs moisture, which promotes the formation of pores in the weld during welding.
B.Higher thermal conductivity and specific heat capacity.
The thermal conductivity and specific heat capacity of aluminum and aluminum alloy are more than twice that of carbon steel and low-alloy steel. During the welding process, a large amount of heat is quickly transferred to the inside of the base metal. Therefore, when welding aluminum and aluminum alloy, the heat is removed Except for the molten metal, more unnecessary consumption is spent on other parts of the metal.
C.The tendency of thermal cracking is high.
The coefficient of linear expansion of aluminum is about 22.9x 10-6/℃, and that of iron is 11.7 x 10-6/℃. The coefficient of linear expansion of aluminum and aluminum alloys is about twice that of carbon steel and low alloy steel. The volume shrinkage rate of aluminum during solidification is large, reaching 6.5%, while iron is 3.5%, so aluminum and aluminum alloys are prone to shrinkage, shrinkage, thermal cracking, and high internal stress during welding.
D.High stomata sensitivity.
Aluminum and aluminum alloy liquid molten pools are easy to absorb hydrogen and other gases. A large amount of gas dissolved at high temperature is too late to precipitate during the cooling and solidification process after welding, and it will form pores in the weld. The moisture in the arc column atmosphere, the moisture absorbed by the welding material and the oxide film on the surface of the base metal are all important sources of hydrogen in the weld.
E.There is no color change during solid liquefaction.
When aluminum and aluminum alloy welding pool metal changes from solid to liquid, there is no obvious color change, which brings inconvenience to the welding operation.
F.Single phase.
Aluminum is a face-centered cubic crystal lattice, no allotrope, no phase change during heating and cooling, the weld grain is easy to be coarse, and the grain cannot be refined through phase change.
Research shows that 5052 aluminum alloy has good friction stir welding performance, dynamic recrystallization occurs in the weld zone, the weld grain is refined, and the weld can reach 0°C to 180°C. Arbitrary bending and optimized process parameters can make the welded joint strength equal to or higher than the base metal.
