Aluminized Sheet: Overview and Welding Performance
Aluminized sheets are steel sheets coated with an aluminum-silicon alloy, offering excellent heat and corrosion resistance. The manufacturing process for aluminized sheets is similar to that of galvanized sheets, but aluminized sheets have better heat resistance. These sheets are commonly used in household appliances, building materials, car mufflers, and more.
1. Introduction to Aluminized Sheets and Welding Performance
Aluminized sheets can be categorized into two types:
- Heat-Resistant Aluminized Sheets: These sheets feature a 20-25µm thick AlSi alloy coating (6-8.5% silicon) on both sides of low-carbon steel. They can withstand temperatures up to 640°C.
- Corrosion-Resistant Aluminized Sheets: These sheets have a thicker coating than the heat-resistant type, typically 2-3 times thicker. They form an AlFe alloy layer for enhanced corrosion resistance.
Aluminized sheets are usually coated through hot-dipping or solid powder processes. The heat-resistant type forms an AlFeSi alloy layer, while the corrosion-resistant type forms an AlFe alloy layer. However, the corrosion-resistant aluminized sheet has poorer weldability due to its thick coating and low melting point.
Aluminized sheets are widely used in industries such as petroleum, chemicals, power, automobiles, and light industries due to their heat, oxidation, and corrosion resistance, as well as their affordability.
2. Challenges in Welding Aluminized Sheets
Welding aluminized sheets can be challenging due to the properties of the aluminum coating. In manual arc welding, using acidic or cellulose electrodes often leads to defects such as pores and bumps in the weld seam. Using alkaline low-hydrogen electrodes helps reduce these defects but may still lead to increased Si and Mn content in the weld, negatively affecting its mechanical properties.
The aluminized layer must be removed before welding to avoid the deterioration of weld quality. Without proper preparation, the weld may require anti-corrosion treatment after welding, as the aluminum coating is critical for ensuring the heat and corrosion resistance of the metal. When using ordinary metal arc welding, while the weld composition meets requirements, the surface may be rough and uneven. Tungsten arc welding helps maintain the integrity of the coating, but the aluminum coating must typically be removed from the weld area to minimize aluminum content in the weld metal.
3. MIG Arc Brazing Process for Aluminized Sheets
The MIG arc brazing process, used with the CLOOS GLC333MC4 welding machine from Germany, offers an effective method for welding aluminized sheets. This process does not require pretreatment or post-welding anti-corrosion treatment. The resulting weld is smooth, flat, and corrosion-resistant. Aluminum bronze welding wire, commonly used for MIG arc brazing, has a low melting point and excellent mechanical properties, making it ideal for maintaining the integrity of the aluminized layer.
MIG arc brazing reduces aluminum coating loss during welding and ensures the coating remains intact, providing a safer and more reliable welding process. This technique is widely used in industries such as shipbuilding, machinery manufacturing, chemicals, and automobiles.
Conclusion
Aluminized sheets are valuable materials due to their heat and corrosion resistance, but their welding requires careful preparation. MIG arc brazing has proven to be the most effective method, offering both excellent weld quality and minimal impact on the aluminized coating.
