What practice helps prevent cracking in tack welds?

• A. Leaving weld craters unfilled
• B. Filling each weld crater adequately to reduce cracking
• C. Using minimal filler metal
• D. Cooling the weld with cold air

Answer: (B)

Filling each weld crater adequately reduces cracking by removing the sharp notch that forms at the end of a tack weld. When the weld cools and contracts, residual tensile stresses concentrate at abrupt geometry like an open crater. If the crater is left unfilled, that notch becomes a ready-made crack path as the metal solidifies and shrinks. By filling the crater, you smooth the transition, lower stress concentration, and promote more uniform solidification, which together greatly reducing the chance of a crack initiating and propagating. Cooling with cold air causes rapid temperature drop and increases residual stresses, and using minimal filler metal leaves unfilled gaps that maintain notch effects, both raising the risk of cracking.