Nitrogen entering the weld pool from the atmosphere can cause which issue?

Nitrogen entering the weld pool from the atmosphere can cause which issue?

• A. Increased hardness
• B. Subsurface porosity and reduced penetration
• C. Faster weld speed
• D. Better corrosion resistance

Answer: (B)

Shielding gas protects the molten weld from the air. If nitrogen from the atmosphere gets into the weld pool, it doesn’t contribute to the weld like the shielding gas should. As the molten metal solidifies, dissolved nitrogen can come out as gas and form bubbles, creating porosity in the weld. When porosity occurs beneath the surface, it’s subsurface porosity, which weakens the weld and can reduce the effective penetration because voids interrupt the solidification and fusion of the weld metal with the base material. Nitrogen entering the weld pool does not increase hardness or corrosion resistance, nor does it inherently speed up welding, so subsurface porosity and reduced penetration are the correct consequences.

Shielding gas protects the molten weld from the air. If nitrogen from the atmosphere gets into the weld pool, it doesn’t contribute to the weld like the shielding gas should. As the molten metal solidifies, dissolved nitrogen can come out as gas and form bubbles, creating porosity in the weld. When porosity occurs beneath the surface, it’s subsurface porosity, which weakens the weld and can reduce the effective penetration because voids interrupt the solidification and fusion of the weld metal with the base material. Nitrogen entering the weld pool does not increase hardness or corrosion resistance, nor does it inherently speed up welding, so subsurface porosity and reduced penetration are the correct consequences.