Technical difficulties in aluminum welding

The technical difficulties of aluminum welding mainly include the following aspects:
Oxide film problem: Aluminum is highly prone to oxidation in air and during welding, and the resulting aluminum oxide (Al2O3) has a high melting point and is very stable, making it difficult to remove. This hinders the melting and fusion of the base material, making it prone to defects such as slag inclusion, incomplete fusion, and incomplete welding. Before welding, strict surface cleaning should be carried out using chemical or mechanical methods, and protection should be strengthened during the welding process to prevent oxidation.
High thermal conductivity: The thermal conductivity and specific heat capacity of aluminum are more than twice that of carbon steel and low-alloy steel. During the welding process, a large amount of heat can be rapidly conducted into the interior of the base metal, resulting in high energy consumption and increased welding difficulty. In order to obtain high-quality welded joints, energy sources with concentrated energy and high power should be used as much as possible, and sometimes preheating and other process measures can also be used.
High coefficient of linear expansion: The coefficient of linear expansion of aluminum and aluminum alloys is about twice that of carbon steel and low-alloy steel. During solidification, the volume shrinkage rate of welded components is relatively high, which can easily lead to shrinkage porosity, thermal cracking, and high internal stress. Measures such as adjusting the composition of welding wire and welding process can be taken in production to prevent the occurrence of hot cracks.
Hydrogen pore problem: Aluminum has strong reflection ability for light and heat, and there is no significant color change when it is in a solid-liquid transition state. At high temperatures, its strength is low and it is easy to weld through. In addition, aluminum and aluminum alloys can dissolve a large amount of hydrogen in the liquid state, and hardly dissolve hydrogen in the solid state. During the solidification and rapid cooling process of the welding pool, hydrogen cannot escape in time and easily forms hydrogen pores.
Welding deformation: The welding deformation and stress of aluminum and aluminum alloys are significant, and measures to prevent welding deformation need to be taken. Deformation and stress can be reduced by standardizing process parameters, preheating in the early stage, and other methods.
Specific measures to address these technical difficulties include:
Surface cleaning: Chemical or mechanical methods are used to remove the oxide film and adsorbed moisture on the surface of aluminum materials, ensuring the smooth progress of the welding process.
Energy concentration: Welding is carried out using energy sources that are concentrated and have high power, such as MIG welding which uses DC reverse connection, AC current, etc.
Preheating and segmented welding: Preheating and segmented welding are used to reduce welding heat input and minimize the expansion of the heat affected zone.
Adjust the composition of the welding wire: Select appropriate welding wire composition, such as aluminum silicon alloy welding wire with moderate silicon content, to reduce the tendency of thermal cracking.
Standardized operation: Strictly follow welding procedures, control environmental humidity, and ensure standardized operation of the welding process