ã€China Aluminum Industry Network】When welding aluminum profiles, there are several key points to keep in mind. First, aluminum is highly prone to oxidation. In the air, it quickly forms a dense layer of Alâ‚‚O₃, which has a high melting point (around 2050°C), much higher than that of aluminum itself (about 600°C). This oxide layer can hinder proper fusion during welding, leading to defects like porosity, slag inclusion, and incomplete fusion, all of which can reduce the quality of the weld.
Second, porosity is a common issue when welding aluminum alloys. The main cause is hydrogen. Liquid aluminum can dissolve a significant amount of hydrogen, but as it solidifies, the hydrogen cannot escape easily, resulting in gas bubbles forming in the weld. Even with high-purity argon (over 99.99%), if the moisture content reaches 20ppm, many pores can still form. High humidity levels (above 80%) can also lead to visible porosity in the weld.
Third, welding aluminum often leads to significant deformation and cracking. The linear expansion coefficient and contraction rate of aluminum are roughly twice that of steel, making internal stresses more likely to develop. Rigid structures are particularly susceptible to hot cracking during the process.
Fourth, aluminum has high thermal conductivity—about four times that of steel. This means more heat is required for welding, and the process can be more challenging compared to steel welding.
Fifth, alloying elements such as magnesium, zinc, and manganese may evaporate under high-temperature arcs, altering the chemical composition of the weld metal and affecting its performance.
Sixth, at high temperatures, aluminum exhibits low strength and plasticity, which can disrupt the formation of the weld metal. In some cases, this can lead to the weld metal collapsing or even penetrating through the joint.
Lastly, one unique challenge is that aluminum does not change color significantly when it melts. Unlike steel, which turns red when heated, aluminum remains gray, making it harder for welders to judge the correct temperature. This lack of visual cue requires extra attention and skill during the welding process.
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