Crater Cracks by Lincoln's Aluminum Expert, Frank Armao.   

Frank Armao

Within the walls of The Lincoln Electric Company are some of the brightest minds in welding, but we wouldn't be The Welding Experts® if it weren't for the expertise of our customers. Learn with us from questions submitted by real customers and answered by the real experts.

Why do you get "crater cracks" in aluminum and how do you prevent them?

Crater cracks happen for two reasons:

• High thermal rate of conductivity
• The concave shape of the crater 

Aluminum cools so fast that it doesn't provide adequate time for the weld bead to flatten or the crater to fill. 

The deep depression of the crater quickly freezes in a concave shape, exerting high tensile stresses on the surrounding metal. It is in this area that a crack will propagate through the weld metal. 

As the weld cools, crater cracking is common if proper steps are not taken to minimize the problem. 

The easiest most common way to prevent cracking in aluminum
Instead of releasing the trigger at the end of the weld, continue to feed wire and reverse the direction of travel back into the already-welded material. 

Weld far enough back to re-weld the entire crater (One inch should be sufficient), and this will increase the deposit in the crater area, changing its shape from concave to convex. 

The convex-shaped crater rapidly cools and reduces the stress on the weld metal in the crater, which causes "crater cracking."  

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