What are the acceptable undercut limits in a weld?

What are the acceptable undercut limits in a weld?

• A. <1.6 mm (1/16") length, <50 mm (2") accumulated in 300 mm (12") length
• B. <2.0 mm (1/8") length, <70 mm (2-3/4") accumulated in 400 mm (16") length
• C. <0.8 mm (1/32") length, <25 mm (1") accumulated in 200 mm (8") length
• D. No restriction

Answer: (A)

Undercut weakens the weld by nibbling into the base metal along the weld toe, reducing the effective throat thickness and creating a potential stress concentration. To keep welds reliable, acceptance criteria limit both how deep or long an individual undercut can be and how much undercut can accumulate over a measured length. The best answer sets a maximum single undercut length of 1.6 mm and a cumulative limit of 50 mm of undercut within a 300 mm section. This means you can have multiple small undercuts as long as their total length within that 300 mm span stays under 50 mm, but no single undercut exceeds 1.6 mm. These limits strike a balance between producing quality welds and allowing minor imperfections that can occur during welding. Other options propose looser or no restrictions, which would permit larger or more numerous undercuts and thus weaken the weld region, so they do not meet the required standard.

Undercut weakens the weld by nibbling into the base metal along the weld toe, reducing the effective throat thickness and creating a potential stress concentration. To keep welds reliable, acceptance criteria limit both how deep or long an individual undercut can be and how much undercut can accumulate over a measured length.

The best answer sets a maximum single undercut length of 1.6 mm and a cumulative limit of 50 mm of undercut within a 300 mm section. This means you can have multiple small undercuts as long as their total length within that 300 mm span stays under 50 mm, but no single undercut exceeds 1.6 mm. These limits strike a balance between producing quality welds and allowing minor imperfections that can occur during welding.

Other options propose looser or no restrictions, which would permit larger or more numerous undercuts and thus weaken the weld region, so they do not meet the required standard.