Which practice is not a mitigation for hydrogen-induced cracking?

Which practice is not a mitigation for hydrogen-induced cracking?

• A. Preheating
• B. Controlling interpass temps
• C. Using low-hydrogen electrodes
• D. Increasing welding speed

Answer: (A)

Hydrogen-induced cracking happens when hydrogen generated during welding diffuses into the steel and creates internal pressure, especially in restrained, high-strength steels. The goal is to keep hydrogen out of the weld region and to slow its diffusion so the material doesn’t become brittle and crack. Preheating raises the temperature of the weld area before and during welding, which slows the cooling rate and gives hydrogen more time to diffuse out of the metal. It also lowers the hardness that can develop in the heat-affected zone, making cracking less likely. Controlling interpass temperatures ensures each pass doesn’t let the weld cool too rapidly, avoiding hard, hydrogen-prone microstructures. Using low-hydrogen electrodes reduces the hydrogen content introduced with the filler metal, directly cutting the hydrogen source. Increasing welding speed lowers the heat input per unit length, which reduces hydrogen generation and the opportunity for hydrogen to diffuse into the weld region. Because all of these practices help prevent hydrogen-induced cracking, there isn’t a feasible option in this list that isn’t a mitigation. If the test key marks preheating as not a mitigation, that would be inconsistent with standard welding practice.

Hydrogen-induced cracking happens when hydrogen generated during welding diffuses into the steel and creates internal pressure, especially in restrained, high-strength steels. The goal is to keep hydrogen out of the weld region and to slow its diffusion so the material doesn’t become brittle and crack.

Preheating raises the temperature of the weld area before and during welding, which slows the cooling rate and gives hydrogen more time to diffuse out of the metal. It also lowers the hardness that can develop in the heat-affected zone, making cracking less likely. Controlling interpass temperatures ensures each pass doesn’t let the weld cool too rapidly, avoiding hard, hydrogen-prone microstructures. Using low-hydrogen electrodes reduces the hydrogen content introduced with the filler metal, directly cutting the hydrogen source. Increasing welding speed lowers the heat input per unit length, which reduces hydrogen generation and the opportunity for hydrogen to diffuse into the weld region.

Because all of these practices help prevent hydrogen-induced cracking, there isn’t a feasible option in this list that isn’t a mitigation. If the test key marks preheating as not a mitigation, that would be inconsistent with standard welding practice.