Chemical composition as per ISO 898-2 for typical grades
| Class | Material and Treatment | C max. | Mn min. | P max. | S max. |
|---|---|---|---|---|---|
| 8 (M16 and below) | carbon steel (may be quenched and tempered) | 0.58 | 0.25 | 0.060 | 0.150 |
| 8 (above <16) | carbon steel quenched and tempered | 0.58 | 0.30 | 0.048 | 0.058 |
| 10 | carbon steel quenched and tempered | 0.58 | 0.30 | 0.048 | 0.058 |
| 12 | carbon steel quenched and tempered | 0.58 | 0.45 | 0.048 | 0.058 |
Hardness requirement as per ISO 898-2 for typical grades
| Hardness scale | Size | Class 8 min. | Class 8 max. | Class 10 min. | Class 10 max. | Class 12 min. | Class 12 max. |
|---|---|---|---|---|---|---|---|
| Vickers, HV | M5 to M16 | 200 | 302 | 272 | 353 | 295 | 353 |
| Vickers, HV | above M16 to M39 | 233 | 353 | 272 | 353 | 272 | 353 |
| Brinell, HB | M5 to M16 | 190 | 287 | 259 | 336 | 280 | 336 |
| Brinell, HB | above M16 to M39 | 221 | 336 | 259 | 336 | 259 | 336 |
| Rockwell, HRC | M5 to M16 | – | 30 | 26 | 36 | 29 | 36 |
ISO 898-2:2012 Mechanical properties of fasteners made of carbon steel and alloy steel – Part 2: Nuts with specified property classes – Coarse thread and fine pitch thread
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