Hydrogen-induced cracking prevention?

Hydrogen-induced cracking prevention?

• A. High-hydrogen electrodes
• B. Low-hydrogen electrodes, proper preheat, and slow cooling
• C. Rapid cooling only
• D. Increasing current

Answer: (B)

Hydrogen-induced cracking is best prevented by reducing the hydrogen that ends up in the weld and by giving that hydrogen a chance to diffuse out as the metal cools. Using low-hydrogen electrodes minimizes the hydrogen content in the weld metal, cutting the amount of hydrogen available to cause embrittlement. Preheating keeps the weld and heat-affected zone hotter during welding, which reduces hydrogen absorption and slows its diffusion, lowering peak stresses. Slower cooling provides time for any diffusible hydrogen to diffuse out before the steel becomes brittle and cracks can form under restraint. Using electrodes with high hydrogen, rapid cooling, or simply increasing current would either add more hydrogen or worsen conditions that promote cracking, so they’re not effective preventive measures.

Hydrogen-induced cracking is best prevented by reducing the hydrogen that ends up in the weld and by giving that hydrogen a chance to diffuse out as the metal cools. Using low-hydrogen electrodes minimizes the hydrogen content in the weld metal, cutting the amount of hydrogen available to cause embrittlement. Preheating keeps the weld and heat-affected zone hotter during welding, which reduces hydrogen absorption and slows its diffusion, lowering peak stresses. Slower cooling provides time for any diffusible hydrogen to diffuse out before the steel becomes brittle and cracks can form under restraint.

Using electrodes with high hydrogen, rapid cooling, or simply increasing current would either add more hydrogen or worsen conditions that promote cracking, so they’re not effective preventive measures.