Welding
ISO 5817 criteria: quality levels B, C and D
In short
ISO 5817:2023 sets, for each weld imperfection, a limit by quality level: D (moderate), C (intermediate) or B (stringent). From the imperfection, the level and the thickness t (or the width b, or the throat a), the calculation gives the permitted limit and compares it with the measured value.
Calculation
Example calculated with the tool’s default values.
Inputs
- Imperfection (ISO 6520-1)
- 1.7 · 5011, 5012 · Undercut
- Quality level
- C: intermediate
- Thickness t (or s)
- 10 mm
Results
- Permitted h, level C
- 0.50 mmh ≤ 0.1·t, maxi 0.5 mm
Worked example
Every value in this section belongs to the example, calculated with the tool’s default values.
- The required level is set by the application code or contract; ISO 5817 does not replace that choice.
Step-by-step calculation
Thickness range
t > 3 mm
t = 10.0 mm
Row 1.7 (5011, 5012), level C
h ≤ 0.1·t, maxi 0.5 mm
0.10 × 10.0 = 1.00 mm → capped at 0.5 mm
1.7 · Undercut
| Level | Limit | Value (mm) |
|---|---|---|
| D | h ≤ 0.2·t, maxi 1 mm | 1.00 |
| C | h ≤ 0.1·t, maxi 0.5 mm | 0.50 |
| B | h ≤ 0.05·t, maxi 0.5 mm | 0.50 |
How to use it
- Pick the imperfection, with its ISO 5817 reference and its ISO 6520-1 designation.
- Pick the quality level: B (stringent), C (intermediate) or D (moderate).
- Enter the thickness t (or s), and depending on the imperfection the bead width b or the throat a.
- Read the permitted limit for the chosen level.
Frequently asked questions
What are the ISO 5817 quality levels (B, C and D)?
Three levels: D (moderate), C (intermediate) and B (stringent). The required level is set by the application code or contract: ISO 5817 does not replace that choice. The calculation gives the limits of all three levels side by side for the chosen imperfection.
What undercut depth does ISO 5817 permit?
Row 1.7 (ISO 6520 5011, 5012), for t > 3 mm: h ≤ 0.2·t, max 1 mm at level D; h ≤ 0.1·t, max 0.5 mm at level C; h ≤ 0.05·t, max 0.5 mm at level B. Example on 10 mm at level C: 0.10 × 10.0 = 1.00 mm, capped at 0.5 mm. From 0.5 to 3 mm, undercut is only permitted as a short imperfection at levels D and C.
What excess weld metal does ISO 5817 permit?
Row 1.9 (502 in ISO 6520-1), butt weld: h ≤ 1 mm + 0.25·b, max 10 mm at level D; h ≤ 1 mm + 0.15·b, max 7 mm at level C; h ≤ 1 mm + 0.1·b, max 5 mm at level B, with b the bead width. For the convexity of a fillet weld (row 1.10), the maxima are 5, 4 and 3 mm.
Are cracks and lack of fusion permitted?
No: crack (1.1), crater crack (1.2), lack of fusion (1.5) and burn-through (1.15) are not permitted at any level. Incomplete root penetration of a single-side butt weld (1.6) is only permitted at level D, as a short imperfection: h ≤ 0.2·t, max 2 mm.
What is a short imperfection?
Over 100 mm of weld, a cumulative imperfection length of 25 mm at most (25 % of the length if the weld is shorter than 100 mm), from definition 3.6 of the standard. Some limits only apply to a short imperfection: the calculation flags it.
Limits
Indicative results. Only the rows of ISO 5817:2023 table 1 read in the standard published by SSAB are offered; internal pores, inclusions and multiple imperfections are outside the tool. For a full-penetration butt weld, s = t. The required level remains that of the application code or contract.
Sources
- ISO 5817:2023 : soudage, niveaux de qualité des imperfections : Tableau 1, ligne 1.7 (ISO 6520-1 5011, 5012) (link)