What is a common cause of porosity in GMAW?

What is a common cause of porosity in GMAW?

• A. Correct shielding gas quantity
• B. Inadequate gas shielding
• C. Excessive shielding gas
• D. No shielding gas

Answer: (B)

Porosity in GMAW happens when the molten weld metal isn’t properly protected from the surrounding air. The shielding gas must blanket the weld pool continuously; if the flow is too low, there are leaks, or the nozzle is too far away (or there are drafts), air can reach the molten metal and form gas pockets as it solidifies. That’s why inadequate shielding is the most common cause—the weld is exposed to contaminants during solidification, creating porosity. If there is no shielding gas at all, porosity would still occur for the same reason. Excessive shielding gas can cause other issues like turbulence or gas scouring, but the essential idea is that the weld requires consistent, sufficient shielding to prevent porosity. Ensure proper flow, check for leaks, maintain the correct nozzle distance, and minimize drafts.

Porosity in GMAW happens when the molten weld metal isn’t properly protected from the surrounding air. The shielding gas must blanket the weld pool continuously; if the flow is too low, there are leaks, or the nozzle is too far away (or there are drafts), air can reach the molten metal and form gas pockets as it solidifies. That’s why inadequate shielding is the most common cause—the weld is exposed to contaminants during solidification, creating porosity. If there is no shielding gas at all, porosity would still occur for the same reason. Excessive shielding gas can cause other issues like turbulence or gas scouring, but the essential idea is that the weld requires consistent, sufficient shielding to prevent porosity. Ensure proper flow, check for leaks, maintain the correct nozzle distance, and minimize drafts.