Preheating near the weld is intended to reduce which risk?

Preheating near the weld is intended to reduce which risk?

• A. Cracking Due to Hydrogen
• B. Corrosion
• C. Thermal Distortion
• D. Electrical Resistance

Answer: (A)

Hydrogen cracking happens when hydrogen produced or absorbed during welding diffuses into the metal and becomes trapped as the weld cools, especially in the heat‑affected zone. Preheating the area near the weld slows the cooling rate, keeping the metal hotter longer and giving hydrogen time to diffuse out before the metal becomes brittle and residual stresses lock in cracks. In short, warmer preheat reduces hydrogen diffusion barriers and lowers the chance that trapped hydrogen will crack the weld as it cools. Corrosion, thermal distortion, and electrical resistance aren’t addressed in the same protective way, so the preheat focus here is specifically on preventing hydrogen-induced cracking.

Hydrogen cracking happens when hydrogen produced or absorbed during welding diffuses into the metal and becomes trapped as the weld cools, especially in the heat‑affected zone. Preheating the area near the weld slows the cooling rate, keeping the metal hotter longer and giving hydrogen time to diffuse out before the metal becomes brittle and residual stresses lock in cracks. In short, warmer preheat reduces hydrogen diffusion barriers and lowers the chance that trapped hydrogen will crack the weld as it cools. Corrosion, thermal distortion, and electrical resistance aren’t addressed in the same protective way, so the preheat focus here is specifically on preventing hydrogen-induced cracking.