During the welding of a hardenable medium-carbon steel crankshaft using a shielded metal arc welding (SMAW) process, the welder observes a characteristic 'pinging' sound shortly after the weld cools. This sound, combined with visible cracking, indicates a severe problem often associated with welding hardenable steels. What mitigating action is most likely to prevent this issue in subsequent welds?

Question: During the welding of a hardenable medium-carbon steel crankshaft using a shielded metal arc welding (SMAW) process, the welder observes a characteristic 'pinging' sound shortly after the weld cools. This sound, combined with visible cracking, indicates a severe problem often associated with welding hardenable steels. What mitigating action is most likely to prevent this issue in subsequent welds?

Answer options:

• Increasing the welding current to achieve deeper penetration
• Decreasing the preheat temperature to speed up cooling ✅ Applying a controlled post-weld heat treatment (PWHT)
• Switching to a larger diameter electrode for single pass welds

Correct answer: Applying a controlled post-weld heat treatment (PWHT)

Explanation: The 'pinging' sound and cracking after welding hardenable steels often indicate hydrogen-induced cracking, which is promoted by rapid cooling and high residual stresses. Applying a controlled post-weld heat treatment (PWHT) can reduce these stresses, temper the hard microstructure, and allow for hydrogen diffusion, thereby preventing cracking. Increasing current or decreasing preheat would exacerbate the problem, and electrode size change isn't the primary solution for this crack type.