Strong reduction ability
The affinity between aluminum and oxygen is very strong, and aluminum is easy to be oxidized in air to synthesize dense and solid A1203 film with a thickness of about 00.1μm. The melting point of A1203 is as high as 2050℃, much higher than the melting point of aluminum and aluminum alloy (500-600 ℃). In the welding process, the oxide film hinders the good bonding between the metals and easily causes slag inclusion. The alumina film also absorbs water and promotes porosity in the weld.
High 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 welding, a large amount of heat is rapidly transferred to the base metal. Therefore, in the welding of aluminum and aluminum alloy, in addition to melting the metal, it is unnecessary to consume other parts of the metal.
Hot crack tendency is large
The linear expansion coefficient of aluminum is about 22.9 x10-6/ ℃, and that of iron is 11.7 x10-6/ ℃. The linear expansion coefficient of aluminum and aluminum alloy is about twice that of carbon steel and low alloy steel. The volume shrinkage rate of aluminum solidification is large, up to 6.5 %, while that of iron is 3.5. Therefore, the shrinkage hole, shrinkage porosity, thermal crack and high internal stress are easily produced when aluminum and aluminum alloy are welded.
High stomatal sensitivity
Aluminum and aluminum alloy liquid pools easily absorb hydrogen and other gases. A large amount of gas dissolved at high temperature does not have time to settle during cooling and solidification after welding. If it accumulates in the weld, it will form pores. The water in the arc column atmosphere and the water adsorbed by the oxide film on the surface of the welding material and base metal are the important sources of hydrogen in the weld.
There is no color change in solid state liquefaction
When the molten pool metal of aluminum and aluminum alloy is changed from solid to liquid, the color change is not obvious, which brings inconvenience to welding operation.
Single phase
5052 aluminum plate aluminum is face-centered cubic lattice, no allotrope, heating and cooling without phase transformation, weld grain is easy to coarse, can not be refined through phase transformation.
The welding characteristics of aluminum alloy 5052 aluminum plate are introduced. 5052 aluminum plate has good friction stir welding performance, dynamic recrystallization of weld area, weld grain refinement, weld can achieve 0℃ to 180℃. The strength of welded joint can reach or be higher than that of base metal by optimizing process parameters.
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