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Advantages and Disadvantages of Laser Welding of Aluminum Alloy

When laser welding aluminum alloy, just like the welding of galvanized steel plate, many pores and cracks will be produced during the welding process, which will affect the welding quality. Aluminum element has low ionization energy, poor welding stability, and will also cause welding discontinuity. In addition to the high heat welding method, aluminum oxide and aluminum nitride will be produced in the whole process, causing pollution to the environment.

However, the aluminum alloy plate surface can be polished before welding to increase its absorption of laser energy; Inert gas shall be used during welding to prevent air holes.

Laser arc hybrid welding of aluminum alloy has solved the problems of laser welding power, absorption of laser beam on the surface of aluminum alloy and threshold value of deep penetration welding. It is one of the most promising aluminum alloy welding processes. At present, the process is not mature and is in the research and exploration stage.

The difficulty of laser welding is different for different aluminum alloys. The non heat treatment strengthened aluminum and aluminum alloy 1000 series, 3000 series and 5000 series have good weldability; 4000 series alloy has very low crack sensitivity; For 5000 series alloy, when ω When (Mg)=2%, the alloy produces cracks. With the increase of magnesium content, the welding performance is improved, but the ductility and corrosion resistance become poor; 2000 series, 6000 series and 7000 series alloys have a large tendency to hot cracking, poor weld formation, and a significant reduction in post weld aging hardness.

Therefore, for the laser welding of aluminum alloy, it is necessary to adopt appropriate process measures and correctly select welding methods and processes to obtain good welding results. Before welding, surface treatment of materials, control of welding process parameters and change of welding structure are all effective methods.

Selection of welding parameters

· Laser power 3KW.

· Laser welding speed: 4m/min. The welding speed depends on the energy density. The higher the energy density, the faster the welding speed.

· When the plate is galvanized (such as 0.8mm for the side wall outer plate and 0.75mm for the top cover outer plate), the assembly clearance is controlled by the center, generally 0.05~0.20mm. When the weld is less than 0.15 mm, the zinc vapor cannot be removed from the side gap, but is removed from the weld surface, which is easy to produce porosity defects; When the weld width is greater than 0.15 mm, the molten metal cannot completely fill the gap, resulting in insufficient strength. When the weld thickness is the same as that of the plate, the mechanical properties are the best, and the weld width depends on the focus diameter; The weld depth depends on the energy density, welding speed and focusing diameter.

· The shielding gas is argon, the flow is 25L/min, and the operating pressure is 0.15~0.20MPa.

· Focus diameter 0.6 mm.

· Focus position: when the plate thickness is 1mm, the focus is just on the upper surface, and the focus position depends on the shape of the cone.