When oxygen and nitrogen from the atmosphere mix in the molten weld metal, they tend to:

When oxygen and nitrogen from the atmosphere mix in the molten weld metal, they tend to:

• A. increase the tensile strength of the weld metal.
• B. form harmful oxides and nitrides in the weld metal.
• C. help increase the ductility of the weld zone.
• D. increase the fracture toughness of the weld metal.

Answer: (B)

Oxygen and nitrogen dissolving into the molten weld pool form oxide and nitride compounds. These compounds are hard and brittle, creating inclusions that disrupt the metal’s continuity and act as sites for cracking or reduced deformation. That brittle character lowers ductility and toughness, and can also weaken the weld rather than increasing strength. So, the presence of these atmospheric gases tends to form harmful oxides and nitrides in the weld metal, not improve its mechanical properties.

Oxygen and nitrogen dissolving into the molten weld pool form oxide and nitride compounds. These compounds are hard and brittle, creating inclusions that disrupt the metal’s continuity and act as sites for cracking or reduced deformation. That brittle character lowers ductility and toughness, and can also weaken the weld rather than increasing strength. So, the presence of these atmospheric gases tends to form harmful oxides and nitrides in the weld metal, not improve its mechanical properties.