According to standard DIN EN ISO 3506
| Steel group | Steel grade | Strength class | Tensile strength Rm1 N/mm2 min. |
0,2% – Yield strength Rp0,21 N/mm2 min. |
Elongation at fracture A2 mm min. |
Hardness | ||
|---|---|---|---|---|---|---|---|---|
| HB | HRC | HV | ||||||
| Martensitic | C1 | 50 | 500 | 250 | 0,2d | 147 – 209 | – | 155 – 220 |
| 70 | 700 | 410 | 0,2d | 209 – 314 | 20-34 | 220 – 330 | ||
| 1104 | 1100 | 820 | 0,2d | – | 36 – 45 | 350 – 440 | ||
| C3 | 80 | 800 | 640 | 0,2d | 228 – 323 | 21 – 35 | 240 – 340 | |
| C4 | 50 | 500 | 250 | 0,2d | 147 – 209 | – | 155 – 220 | |
| 70 | 700 | 410 | 0,2d | 209 – 314 | 20-34 | 220 – 330 | ||
| Ferritic | F13 | 45 | 450 | 250 | 0,2d | 128 – 209 | – | 135 – 220 |
| 60 | 600 | 410 | 0,2d | 171 – 271 | – | 180 – 285 | ||
Notes to the table
- 1The tensile strength (Rm) refers to the stress cross-section, while the yield strength (Rp0,2) refers to the value corresponding to 0,2% permanent deformation.
- 2The elongation at fracture is determined by the actual length of the screw. “d” is the nominal diameter.
- 3The nominal diameter of the screw thread “d” is less than or equal to 24 mm.
- 4Hardening with a tempering temperature of at least 275 °C.
What the values apply to
These values apply only to fasteners whose length is not more than 8 x the nominal diameter of the screw thread (8 x d), in strength classes A1-70, A2-70 and A4-70, A1-80, A2-80, A4-80 as well as F1-60. There is no dimensional restriction for fasteners of the following strength classes: A1-50, A2-50, A4-50, C1-50 and C4-50 (in soft condition), nor for the following strength classes: C1-70, C4-70 and C3-80 (in hardened condition). For longer, cold-formed fasteners the values differ from those given in the table; in such cases the strength values must be agreed between the customer and the supplier.
The values given in the table apply to threaded fasteners (screws, nuts, studs) made of stainless and acid-resistant steel, as finished products.
Provided that the following conditions are met:
- The nominal diameter of the screw thread is 1,6 – 39 mm
Nuts of any shape and any design, provided that:
- The widths across flats and the outer cross-section are not smaller than 1,45 x the nominal diameter of the screw thread
- The thread length is at least 0,6 x the nominal diameter of the screw thread.
Temperature limits
On the basis of their mechanical properties, certain steel groups can also be used at temperatures from –200 °C up to +800 °C. In such cases, however, the mechanical and corrosion-resistance characteristics must always be agreed separately with the supplier.
However, extreme temperature conditions may affect the corrosion resistance as well as the mechanical strength values, therefore for use at higher temperatures, or at temperatures below 0°C, the customer and the supplier need to agree on the mechanical properties of the steel!
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