What is burn-through in MIG welding?

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 happens when the heat from the MIG welding arc is high enough to melt all the way through the base metal, creating a hole from the top surface to the bottom. This usually occurs on thin material or when the heat input is too great for the thickness, the weld is held too long, or there’s insufficient backing to support the weld. It’s different from merely melting the surface, which would indicate too little penetration or poor fusion, and it’s not the same as cracking after cooling or porosity, which are separate defects that occur during cooling or due to gas entrapment. To prevent it, reduce heat input, increase travel speed, adjust wire size or voltage, and use proper backing or joint setup.

Burn-through happens when the heat from the MIG welding arc is high enough to melt all the way through the base metal, creating a hole from the top surface to the bottom. This usually occurs on thin material or when the heat input is too great for the thickness, the weld is held too long, or there’s insufficient backing to support the weld. It’s different from merely melting the surface, which would indicate too little penetration or poor fusion, and it’s not the same as cracking after cooling or porosity, which are separate defects that occur during cooling or due to gas entrapment. To prevent it, reduce heat input, increase travel speed, adjust wire size or voltage, and use proper backing or joint setup.