Which practice mitigates hydrogen-induced cracking in welds?

Which practice mitigates hydrogen-induced cracking in welds?

• A. Increasing welding speed
• B. Preheating the weld area
• C. Using high-hydrogen electrodes
• D. Post-weld painting

Answer: (B)

Hydrogen-induced cracking happens when hydrogen atoms generated during welding diffuse into the metal and become trapped at microstructural features as the weld cools, creating pressures that crack the metal. Preheating the weld area raises the temperature during and after welding, which slows the cooling rate and gives hydrogen more time to diffuse out before cracks form. This reduces the concentration of hydrogen in susceptible regions and lowers the hardness developed in the heat-affected zone, both of which lessen the likelihood of cracking. In contrast, increasing welding speed cools the weld more quickly, which can trap hydrogen and increase cracking risk; using high-hydrogen electrodes adds more hydrogen to the weld metal; post-weld painting does not address hydrogen in the weld region.

Hydrogen-induced cracking happens when hydrogen atoms generated during welding diffuse into the metal and become trapped at microstructural features as the weld cools, creating pressures that crack the metal. Preheating the weld area raises the temperature during and after welding, which slows the cooling rate and gives hydrogen more time to diffuse out before cracks form. This reduces the concentration of hydrogen in susceptible regions and lowers the hardness developed in the heat-affected zone, both of which lessen the likelihood of cracking.

In contrast, increasing welding speed cools the weld more quickly, which can trap hydrogen and increase cracking risk; using high-hydrogen electrodes adds more hydrogen to the weld metal; post-weld painting does not address hydrogen in the weld region.