Aluminium alloys are popular for a wide range of applications, however, there is a common misconception that aluminium can be fabricated through the conventional methods used in mild steel applications.
Aluminium fabrication plays an essential role in metal fabrications for a variety of industries. The metal’s light weight, corrosion resistance, and ductility make it ideal for many applications from automotive parts to medical devices.
Aluminium isn’t always easy to work with. The appropriate practices and equipment is necessary if you want to avoid welding defects or damage. The choice of alloy, welding gas and joining method can all have a significant effect on the quality of finished products.
Figure 1 Aluminium Sheet
Due to aluminium’s unique characteristics, aluminium fabrication differs from the other metals. Low weight density of aluminium is common knowledge which brings various advantages and disadvantages in the fabrication. Although aluminium has a weaker mechanical properties, it still possesses higher strength to weight ratio compared to stainless steel and carbon steel in various applications.
2. Mechanical Processing of aluminium
Cold processing of aluminium such as bending, cutting, shaping is often easier compared to mild steel due to its relatively weak strength characteristics. However its soft nature brings some challenges as well.
Due to its low melting point, grinding of aluminium is a very delicate operation because it starts melting in low temperature.
Low strength of the aluminium requires less force for shaping operations compared to mild steel and stainless steel.
3. Aluminium Welding
Aluminium has a great thermal conductivity and lower melting point compared to the mild steel therefore it requires a more delicate welding process in order to avoid burning through the work piece. Similarly, aluminium welding wire has smaller material strength which might get easily tangled during the welding process.
Figure 2 Aluminium Weld
Before starting aluminium welding, it is essential to adequately clean the base metal to ensure all aluminium oxide has been cleaned off the surface. The melting point of the aluminium oxide is significantly higher than the melting point of the base metal which might cause the presence of aluminium oxide to disrupt welding. Also aluminium requires higher amperage and voltage compared to mild steel which requires a faster welding. Welders who are accustomed to welding carbon steel will require to adapt their welding pace to aluminium. Slow welding of aluminium poses burn through especially for thin aluminium sheets.
4. Ideal Weldable Aluminium Alloys?
Aluminium alloys have different welding characteristics.2XXX and 7XXX series alloys are often used in aerospace applications and they have very high strength. Due to their copper and zinc ratio, these alloys prone to cracking therefore they require extra precautions for welding application.
On the other hand 6XXX series have less strength but better physical characteristics. They are more easily welded compared to 2XXX and 7XXX series.
4XXX series alloys often used as a filler material for welding other aluminium alloys. The silicon content significantly reduces their melting point and allows them to emerge as a filler material.
5XXX, 3XXX and 1XXX alloys are generally offer good weldability for particular situations.
Aluminium poses has significant different metallurgical characteristics which requires different fabrication procedures than mild and stainless steel. Considering the dominance of carbon steel applications in metal fabrication, aluminium fabrication requires an eye for detail and more delicate processing application. Material knowledge and manufacturing expertise with aluminium are very crucial when selecting a contractor for aluminium fabrications.