Welding characteristics of aluminum alloy by fiber laser welding machine

At present, conventional methods such as TIG welding and MIG welding are mainly used to weld aluminum alloy. When welding by conventional methods, the large heat input leads to wide welds and shallow penetration. Aluminum alloys have fast thermal conductivity. During metallurgy, a large amount of hydrogen dissolved at high temperature does not have time to overflow and produce hydrogen pores (the pores formed by the precipitation of hydrogen dissolved in the molten pool are called metallurgical pores; the pores formed by the decomposition of hydrogen from the water in the oxide film that is not completely melted due to heat decomposition are called oxide film pores); due to the fast metallurgical speed, the weld metal grains are coarse, and the softening of the weld joint can reduce the strength by up to 40%; the aluminum alloy has a low melting point and fast thermal conductivity, and the molten metal has poor fluidity, which makes the weld shape unsightly; the heating area is large, and the processed material is easily deformed, which affects the processing size accuracy. The quality of conventional welding of aluminum alloys is difficult to guarantee, and the welding speed is difficult to meet the requirements of mass production.

With the improvement of the popularization level of laser processing application, the use of fiber laser welding machine to weld aluminum alloy has small heat input and concentrated heat source. Especially after the advent of fiber laser, the energy density of laser welding aluminum alloy is more concentrated, the laser wavelength is shorter, and the high reflection is improved. Through laser wire filling, laser-MIG composite welding, double spot laser welding and other processes, the forming effect of aluminum alloy welding can be significantly improved, and the welding quality is improved.

Regardless of the welding method, the preparation work before aluminum alloy welding is essential and has a great impact on the welding quality of aluminum alloy. Before welding, wipe the surface of aluminum alloy parts with anhydrous alcohol or acetone to remove impurities such as water or oil adsorbed on the surface. To prevent the workpiece from being oxidized in the air, the workpiece needs to be mechanically polished or chemically treated and dried to complete the welding as soon as possible. In order to speed up the molten pool fluidity during aluminum alloy welding, a copper plate can be added to the back of the aluminum alloy workpiece to improve the weld formation. During welding, Ar gas protection is used to isolate the air, which can reduce the generation of pores.

Specific measures to optimize the quality of laser welding aluminum alloy

At the beginning of the welding of aluminum alloy fiber laser welding machine, there is a high reflection phenomenon, which seriously affects the material's absorption of laser energy. The shorter the wavelength, the better the material absorbs light. Therefore, fiber laser absorbs aluminum alloy better than CO2 laser. The beam mode of fiber laser is also better than CO2 laser, and the energy density is more concentrated. Once the material begins to absorb light energy, the reflectivity of liquid metal to light decreases significantly.

The use of double-spot laser welding can significantly improve the porosity, mainly because when using double beams for welding, the two beams form a relatively large keyhole, which improves the stability of the keyhole and is conducive to the escape of gas; compared with serial double beams, when using parallel double beams for welding, the temperature gradient inside the molten pool is smaller, which reduces the solidification speed of liquid metal and prolongs the escape time of bubbles, which is conducive to reducing the tendency of pores; parallel double beam laser welding can also improve the stability of wire feeding, which is beneficial to stabilizing welding quality.

Compared with aluminum alloy laser self-melting welding, laser wire welding can achieve better forming. Laser welding with filler wire can be compatible with the high energy density of laser welding and the high bridging ability of filler wire welding, and can ensure good forming effects for welds with certain gaps. Moreover, through the selection of different filler materials, different chemical metallurgy can be performed on the parent material, which can play a certain role in supplementing and strengthening alloy elements.