→ Not acceptable – must grind out crack and reweld. 8. Summary Table – Quick Reference (Steel, t = 5–30 mm) | Irregularity | B1 (tight) | B2 (medium) | B3 (loose) | |--------------------------------|--------------------------------|-------------------------------|--------------------------------| | Undercut depth | ≤ 0.3 mm | ≤ 0.5 mm | ≤ 1.0 mm | | Excess weld (butt) | ≤ 1 + 0.1×a | ≤ 2 + 0.15×a | ≤ 3 + 0.2×a | | Misalignment (butt) | ≤ 0.1×t (max 1 mm) | ≤ 0.15×t (max 2 mm) | ≤ 0.25×t (max 3 mm) | | Surface porosity (visible) | None or 1 pore / 100 mm | 2 pores / 50 mm | Scattered, <1 mm | | Crater cracks | Not allowed | Not allowed | ≤0.5 mm isolated only | | Incomplete fusion | Not allowed | ≤0.5 mm deep, local | ≤1 mm deep, local | 9. Final Recommendation When a drawing says "DIN 8570-B", immediately clarify the quality grade (B1, B2, or B3). In most modern welding quality management, convert to ISO 5817 or ISO 13920 for traceability. For training or inspection, use DIN 8570-B as a legacy baseline – not a replacement for EN/ISO standards. Would you like a printable checklist or a comparison table with AWS D1.1 as well?