How can crater cracks be prevented at the end of a weld?

• A. Taper off amperage gradually before stopping the weld
• B. Stop abruptly
• C. Increase amperage at end
• D. Pause without changing amperage

Answer: (A)

Crater cracks form when the end of a weld cools too quickly or unevenly, creating tensile stresses as the last molten metal solidifies. Controlling heat input as you finish is the key to preventing that.

Tapering off amperage gradually before stopping reduces the heat and slows cooling at the weld’s end. This smoother transition gives the molten end time to fill and solidify more evenly, lowering residual stresses that would otherwise cause a crater crack. Stopping abruptly increases the cooling rate and can trap stress in the crater, making cracks more likely. Increasing amperage at the end or pausing without changing amperage either keeps heat too high or doesn’t reduce the abrupt cooling, which doesn’t help prevent cracks.