Common Copper Alloy Welding Defects
Because the weldability of copper alloys changes so much, it can be intimidating. Let’s explore some of the more common defects and how to avoid them.
Copper and its alloys are most susceptible to this defect. Pure coppers, brasses, phosphor bronzes, copper nickels, and aluminum bronzes are particularly so.
In order to combat porosity in coppers, phosphor bronzes, and copper nickels, do not use autogenous welding with a matching filler. Instead, use filler wire containing deoxidants, such as aluminum, silicon, manganese, titanium, or phosphorous.
Phosphor bronzes are best paired to fillers with a high level of deoxidants.
Copper nickels are best paired with fillers containing 0.2-0.5% titanium.
Reduce the risk of porosity in brasses by using a zinc-free filler. Either a silicon bronze or an aluminum bronze filler is best suited with brasses. Additionally, higher welding speeds reduces pore size in the weld.
Aluminum bronze alloys have a strong aluminium oxide film that forms on their surface. This film gives them strong corrosion resistance. But it also causes oxide film entrapment which increases its risk of porosity. Remove the film to prevent this. Rigorously clean the material surface with wire brushes or scrapers before welding these alloys.
Lack of Fusion
Brasses with less than 20% zinc are vulnerable to fusion defects because of their high thermal conductivity. Therefore, preheat low-zinc alloys before welding.
Aluminum bronzes are also susceptible to lack of fusion due to the aforementioned aluminium oxide film. Again, it’s crucial to thoroughly clean the surface to remove this film before welding.
Coppers containing chromium or beryllium alloys, brasses, and aluminum bronzes with low aluminum content, less than 8.5%, are susceptible to hot cracking. Carefully preheat coppers with chromium/beryllium and aluminum bronzes to reduce the risk. However, brasses containing high levels of zinc don’t require preheating. Unlike their low-zinc counterparts, slow cooling rates can reduce their cracking risk.