Aluminum and aluminum alloys are widely used in construction, transportation, automotive, electronics, packaging and aerospace fields due to their light weight, high strength and corrosion resistance. With the development of technology, aluminum alloy welding process has been enhanced. Laser welding is a commonly used welding technology in the current market, which has the advantages of concentrated high-power heat source, small heat-affected zone, less deformation, energy saving and consumption reduction.
In the daily welding process, due to the special properties of aluminum, laser welding of aluminum and aluminum alloy will be difficult to control the laser focus and the molten pool; when the welder sets the process parameters improperly or lack of rich experience, there may be porosity, cracking and deformation, blackening of the weld and biting edges do not merge and other problems, which seriously affects the quality of the weld and its performance. Next, we will introduce the difficulties and solutions encountered in welding aluminum.
Porosity
The main problem encountered when welding aluminum with a laser is porosity. During the welding process, the laser beam causes fluctuations in the molten metal, and when the gas trapped in the metal expands and spills out, porosity occurs. In addition, the aluminum oxide film prevents the bonding of the metals, adsorbs moisture, and is susceptible to impurities, which contributes to the formation of porosity.
The formation of porosity leads to weakened welds, reduced corrosion resistance and unsightly welds. In general, the following measures are recommended:
Adjust the appropriate laser power to ensure uniform heat input.
When welding thin plates, it is recommended to increase the speed to reduce the time of gas expansion in the metal; when welding thick plates, the welding speed can be reduced to ensure the performance of the weld seam under the condition of material preheating.
Clean the weld surface chemically or mechanically to minimize the effect of impurities on weld quality.
Control the use of shielding gas or flux to reduce oxidation and the amount of gas formed.
Thermal Cracking
Due to the high temperatures generated during the welding process, this can cause rapid expansion and contraction of aluminum and create stress points. If the solidification interval of the weld is too short and the stress points are not released, they can lead to cracking of the aluminum and thermal cracking; in addition, oxidation and thermal cracking can occur easily when the weld is not well protected.
To avoid this, we need to control the heat during the welding process, preheat the weldment sufficiently before welding, and adjust the protective gas.
Blackening of weld seam
Blackening of laser welded aluminum is mainly caused by insufficient laser power, unfocused amount not adjusted to the right value, or damaged laser lens. In this case, the laser energy does not reach the melting threshold of the oxide layer on the surface of the aluminum, causing the aluminum to mix with air and impurities, resulting in blackening of the weld.
In order to get better welding quality and aesthetics, during the aluminum welding process, Mytronic suggests firstly, selecting the right power and setting the correct amount of defocus; secondly, you can also check whether the protective lens is damaged.
Bite edge not fused
When laser welding aluminum, discontinuous, rough and uneven weld paths and uneven ripples are a typical phenomenon. The main reasons are too large assembly gap of the weldment, laser spot shift, insufficient laser power and too much defocus.
Firstly, we can reduce the root clearance of the welded workpiece; secondly, we can adjust the laser beam focus to determine the correct spot position; in addition, we can also increase the laser power and adjust the off-focus amount of the positive focus position, to ensure the quality of the weld after the melting of aluminum.
Due to the special characteristics of aluminum, the process of laser welding will also encounter other problems. Before welding aluminum and aluminum alloys, we should not only consider the stability of the welding quality, but also the appearance of the welding effect. With the improvement of laser technology and aluminum manufacturing technology, the process of laser welding aluminum has also been greatly improved, providing a solid foundation for creating lightweight metal structural components in automotive, aerospace and other fields.
