Define porosity in a weld and name common causes in MIG welding.

Define porosity in a weld and name common causes in MIG welding.

• A. Porosity is gas-entrapped voids in weld metal; caused by moisture only.
• B. Porosity is gas-entrapped voids in weld metal; caused by high linear speed.
• C. Porosity is gas-entrapped voids in weld metal; caused by moisture, oil/grease, dirty metal, or poor shielding gas coverage or leaks.
• D. Porosity is the absence of any voids in the weld.

Answer: (C)

Porosity means gas-entrapped voids in the weld metal that form as the weld pool solidifies. In MIG welding, these pores show up when the molten metal is contaminated or not fully shielded. Contaminants like moisture on the workpiece or on the welding wire, oil or grease, and dirty metal can release gases into the melt. If the shielding gas coverage is poor or there are leaks, the protective blanket doesn’t fully protect the weld, allowing atmospheric gas to be trapped as the metal cools. This combination of gas sources and shielding issues creates the pores, weakening the weld. The other options don’t fit: moisture alone isn’t the only cause, high travel speed isn’t a primary cause of porosity, and porosity is defined by the presence of voids, not their absence.

Porosity means gas-entrapped voids in the weld metal that form as the weld pool solidifies. In MIG welding, these pores show up when the molten metal is contaminated or not fully shielded. Contaminants like moisture on the workpiece or on the welding wire, oil or grease, and dirty metal can release gases into the melt. If the shielding gas coverage is poor or there are leaks, the protective blanket doesn’t fully protect the weld, allowing atmospheric gas to be trapped as the metal cools. This combination of gas sources and shielding issues creates the pores, weakening the weld.

The other options don’t fit: moisture alone isn’t the only cause, high travel speed isn’t a primary cause of porosity, and porosity is defined by the presence of voids, not their absence.