Which factor is most associated with porosity formation in a weld?

Which factor is most associated with porosity formation in a weld?

• A. Hydrogen or vapors from surface contaminants entering weld pool.
• B. Too little heat.
• C. Excess filler metal.
• D. Over-shielding gas.

Answer: (A)

Porosity happens when gas becomes trapped in the weld as it solidifies. The most common gas causing porosity is hydrogen, which enters the weld pool from moisture or vapors on the surface—things like damp metal, oil, grease, cleaning solvents, rust, or flux residues. Hydrogen dissolves in the molten metal and, as the weld cools, forms tiny gas pockets that become pores in the solid weld. That’s why keeping parts clean and dry, preheating when needed, and using proper low-hydrogen materials and shielding practices are crucial to preventing porosity. The other factors listed don’t consistently cause porosity: too little heat tends to produce poor fusion rather than trapped gas; excess filler metal affects geometry and may cause other defects; over-shielding gas can cause instability or turbulence but is not the primary driver of porosity like hydrogen from surface contaminants is.

Porosity happens when gas becomes trapped in the weld as it solidifies. The most common gas causing porosity is hydrogen, which enters the weld pool from moisture or vapors on the surface—things like damp metal, oil, grease, cleaning solvents, rust, or flux residues. Hydrogen dissolves in the molten metal and, as the weld cools, forms tiny gas pockets that become pores in the solid weld. That’s why keeping parts clean and dry, preheating when needed, and using proper low-hydrogen materials and shielding practices are crucial to preventing porosity. The other factors listed don’t consistently cause porosity: too little heat tends to produce poor fusion rather than trapped gas; excess filler metal affects geometry and may cause other defects; over-shielding gas can cause instability or turbulence but is not the primary driver of porosity like hydrogen from surface contaminants is.