ISO 898-1Stud bolt
ISO 898-1
The property class system behind every metric bolt. The first number is tensile strength ÷ 100 MPa, the second is the yield-to-tensile ratio × 10 — so 8.8 means 800 MPa tensile and 80 % of that as yield.
- Base material
- Carbon steel and alloy steel
- Heat treatment condition
- 4.6 and 5.6 as rolled; 8.8, 10.9 and 12.9 quenched and tempered
- Hardness, max
- See the Vickers range in the last column — hardness is how the class is verified in practice
Service temperature
-20 °C+300 °C−273+900 °C
Class 12.9 is vulnerable to hydrogen embrittlement. Do not electroplate it without a documented bake-out, and avoid it in wet H₂S entirely.
Chemical composition
| Element | Min (% by weight) | Max (% by weight) | Notes |
|---|---|---|---|
| C | — | 0.55 | 8.8 |
| P | — | 0.025 | 8.8 – 12.9 |
| S | — | 0.025 | 8.8 – 12.9 |
| B | — | 0.003 | 8.8 – 12.9 |
Mechanical properties
| Diameter | Tensile strength, min | Yield strength, min | Elongation, min | Reduction of area, min |
|---|---|---|---|---|
| Class 4.6 | 400 MPa | 240 MPa | 22 % | ≥ 120 HV |
| Class 5.6 | 500 MPa | 300 MPa | 20 % | ≥ 155 HV |
| Class 8.8 (≤ M16) | 800 MPa | 640 MPa | 12 % | 250–320 HV |
| Class 8.8 (> M16) | 830 MPa | 660 MPa | 12 % | 255–335 HV |
| Class 10.9 | 1 040 MPa | 940 MPa | 9 % | 320–380 HV |
| Class 12.9 | 1 220 MPa | 1 100 MPa | 8 % | 385–435 HV |
Recommended coatings
Equivalent grades
- DIN 267-3
- EN ISO 898-1
- SAE J429 (gan tuong duong: Gr5 ≈ 8.8, Gr8 ≈ 10.9)
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