Which option correctly identifies the method used to avoid burn-through in a vehicle open butt joint weld?

Which option correctly identifies the method used to avoid burn-through in a vehicle open butt joint weld?

• A. Double pass welds
• B. Full-penetration weld
• C. Stitch welds
• D. Lap welds

Answer: (C)

Controlling heat input is essential when welding thin vehicle body panels. Burn-through occurs when the molten metal penetrates through the sheet, especially on open butt joints where there isn’t extra material to absorb heat. Using stitch welds—a series of small, spaced welds with brief pauses between them—limits heat buildup at any single spot and allows each weld segment to cool before the next is made. This approach minimizes the risk of burning through while still maintaining seam strength and proper alignment. The other options increase heat in the joint: a continuous or double-pass weld adds more heat, which raises the chance of burn-through on thin metal; a full-penetration weld concentrates heat to achieve complete fusion through the thickness, which is often unnecessary and riskier on thin panels; lap welds involve overlapping layers and can require more heat and handling of fit-up, making them less suited to preventing burn-through in an open butt joint on vehicle bodies.

Controlling heat input is essential when welding thin vehicle body panels. Burn-through occurs when the molten metal penetrates through the sheet, especially on open butt joints where there isn’t extra material to absorb heat. Using stitch welds—a series of small, spaced welds with brief pauses between them—limits heat buildup at any single spot and allows each weld segment to cool before the next is made. This approach minimizes the risk of burning through while still maintaining seam strength and proper alignment.

The other options increase heat in the joint: a continuous or double-pass weld adds more heat, which raises the chance of burn-through on thin metal; a full-penetration weld concentrates heat to achieve complete fusion through the thickness, which is often unnecessary and riskier on thin panels; lap welds involve overlapping layers and can require more heat and handling of fit-up, making them less suited to preventing burn-through in an open butt joint on vehicle bodies.