A fabricator is visually inspecting a structural steel assembly for bridge construction. The welding procedure specification (WPS) calls for E7018 electrodes and specific preheat temperatures. During inspection, several short, transverse cracks are observed in the weld toes shortly after cooling. What is the most probable cause of these defects, given the electrode type and potential for insufficient preheat/post-weld cooling control?

Question: A fabricator is visually inspecting a structural steel assembly for bridge construction. The welding procedure specification (WPS) calls for E7018 electrodes and specific preheat temperatures. During inspection, several short, transverse cracks are observed in the weld toes shortly after cooling. What is the most probable cause of these defects, given the electrode type and potential for insufficient preheat/post-weld cooling control?

Answer options:

• Excessive welding current leading to burn-through. ✅ Too rapid cooling leading to hydrogen-induced cracking (cold cracking).
• Insufficient shielding gas coverage causing oxidation.
• Incorrect electrode classification causing incomplete fusion.

Correct answer: Too rapid cooling leading to hydrogen-induced cracking (cold cracking).

Explanation: Transverse cracks at the weld toe, especially in high-strength steels and when using low-hydrogen electrodes like E7018, are often indicative of hydrogen-induced cracking (cold cracking). This typically occurs due to the combination of diffusible hydrogen, susceptible microstructure, and high residual stresses exacerbated by rapid cooling. Insufficient preheat or controlled cooling can contribute to this issue.