What is hydrogen-induced cracking and how can it be prevented in welding?

• A. Cracking due to hydrogen in the weld metal or heat-affected zone; prevented with low-hydrogen electrodes, preheat, and proper cooling.
• B. Cracking caused by hydrogen embrittlement after painting.
• C. Cracking due to impurities in shielding gas.
• D. Cracking only occurs in aluminum alloys.

Answer: (A)

Hydrogen-induced cracking is a weld failure caused when diffusible hydrogen enters the weld metal or heat-affected zone during welding and, under the tensile stresses present as the metal cools, forms brittle microcracks that can grow and split the joint. The hydrogen tends to diffuse to stressed areas and grain boundaries, so it’s especially risky in high-strength steels and thick sections with high residual stresses. Prevention centers on keeping hydrogen out of the weld and controlling cooling so hydrogen can escape rather than being trapped. Using low-hydrogen consumables, keeping filler metal and flux dry (baking and proper storage), preheating the joint, maintaining appropriate interpass temperatures, and ensuring slower, controlled cooling all reduce hydrogen uptake and allow diffusion out of the metal. Post-weld heat treatment can relieve stresses in some materials. Other options describe problems that aren’t caused by this mechanism—cracking after painting, impurities in shielding gas, or cracking only in aluminum alloys—so they don’t fit the described hydrogen-induced cracking scenario.