What is burn-through in MIG welding?

• A. Melting completely through the base metal
• B. Melting only on surface
• C. Cracking after cooling
• D. Producing porosity

Answer: (A)

Burn-through in MIG welding is when the heat from the arc melts the base metal all the way through, creating a hole in the material rather than just fusing the surfaces. This happens most often on very thin sheet metal or when heat input is too high or travel speed is too slow, which concentrates too much heat in one spot. It’s not simply melting the surface, and it’s not cracking after cooling or forming porosity. To prevent it, adjust the welding parameters (lower voltage/current, increase travel speed), control the arc length and wire feed, and consider using a backing plate or heat sink or changing the joint design to limit penetration.