What is crater cracking, and how can it be prevented?

What is crater cracking, and how can it be prevented?

• A. Cracks forming in the crater at end of weld; prevented by backfilling the crater or performing a small restart/stop-off.
• B. Cracks in the base metal away from the weld; prevented by cooling.
• C. Cracks along the weld toe caused by over-welding.
• D. Cracking only occurs during preheating.

Answer: (A)

Crater cracking occurs when a crack forms in the crater at the end of a weld bead as the molten metal cools and contracts. The end of the weld undergoes a high thermal gradient and residual tensile stresses, and if the crater is left open, the final solidifying metal can initiate a crack. Preventing it comes down to finishing the weld in a way that ties in that final portion of metal. Backfilling the crater with a little more weld metal as you finish, or making a short restart/stop-off to close the crater, helps relieve those stresses and creates a smoother end to the weld. This reduces the chance of a crack starting at the weld’s termination. The other scenarios described refer to different cracking issues that aren’t crater cracking, such as cracks in base metal away from the weld, cracks along the weld toe from excessive welding, or cracking that occurs only during preheating.

Crater cracking occurs when a crack forms in the crater at the end of a weld bead as the molten metal cools and contracts. The end of the weld undergoes a high thermal gradient and residual tensile stresses, and if the crater is left open, the final solidifying metal can initiate a crack.

Preventing it comes down to finishing the weld in a way that ties in that final portion of metal. Backfilling the crater with a little more weld metal as you finish, or making a short restart/stop-off to close the crater, helps relieve those stresses and creates a smoother end to the weld. This reduces the chance of a crack starting at the weld’s termination.

The other scenarios described refer to different cracking issues that aren’t crater cracking, such as cracks in base metal away from the weld, cracks along the weld toe from excessive welding, or cracking that occurs only during preheating.