Aluminum and aluminum alloys are widely used in the fields of construction, transportation, automobile, electronics, packaging and aerospace due to their light weight, high strength and corrosion resistance. With the development of technology, aluminum alloy welding process has been improved. At present, laser welding is a welding technology commonly used in the market, it 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 alloys will be difficult to control the laser focus and molten pool; When the welding process parameters are not set properly or the operation experience is insufficient, there may be problems such as porosity, cracking and deformation, blackening of the weld seam, lack of fusion, which seriously affect the welding quality and performance. Next, we will introduce the difficulties and solutions of the welding aluminum materials.
Porosity is the main problem encountered when welding aluminum alloys with laser welding machines. During the welding process, the laser beam causes the metal in the molten pool to fluctuate, and when the gas trapped in the metal expands and overflows, porosity will appear; In addition, the aluminum oxide film will hinder the bonding between the metals, absorb moisture and easily generate impurities, prompting porosity are formed.
The generation of porosity will lead to weakened weld strength, reduced corrosion resistance, and unsightly welds. In general, the following measures are recommended:
1. Adjust the appropriate laser power to ensure uniform heat input.
2. When welding thin plates, it is recommended to increase the speed to reduce the time for gas to expand in the metal; when welding thick plates, the welding speed can be reduced to ensure the performance of the weld when the material is preheated.
3. Use chemical or mechanical methods to clean the surface of the weld seam to reduce the impact of impurities on the welding quality.
4. Control the use of shielding gas or flux to reduce oxidation and gas formation.
2. Thermal crack
The high temperatures generated by the welding process cause the aluminum to expand and contract rapidly, and create stress points. If the welding seam solidification interval is too short and the stress points are not released, they will cause the aluminum to crack and appear thermal cracks; in addition, when the welding seam protection effect is not good, it will also be prone to oxidation and appear thermal cracks.
In order to avoid this situation, we need to control the heat during the welding process, fully preheat the welding workpiece before welding, and adjust the shielding gas.
The blackening of laser welding aluminum is mainly caused by insufficient laser power, improper adjustment of the defocus amount, or damage to the laser lens. In this situation, the energy of the laser fails to reach the melting threshold of the oxide layer on the aluminum material surface, causing the aluminum to mix with air and impurities, resulting in blackening of the welded part.
In order to better obtain the quality and aesthetics of welding, during the process of aluminum welding, we suggest that you first choose the appropriate power and set the correct amount of defocus; secondly, you can also check whether the protective lens is damaged.
4. Lack of fusion
When laser welding aluminum, discontinuous, rough and uneven weld bead is a typical phenomenon. The main reasons are excessive assembly gap of welding workpiece, laser spot offset, insufficient laser power and excessive defocus.
First, we can reduce the root gap of the welding workpiece; second, adjust the focus of the laser beam to determine the correct spot position; in addition, we can also increase the laser power and adjust the positive focus position of the defocus to ensure the welding after aluminum melting quality.
Due to the particularity of aluminum, other problems will be encountered in the laser welding process. Before welding aluminum and aluminum alloys, not only the stability of welding quality, but also the appearance of welding should be considered. 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 parts in the automotive, aerospace and other fields.
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