The standard high-tensile bolt class — general structural and machine fasteners. Medium-carbon (or boron) steel, quenched & tempered.
| Property | Typical value |
|---|---|
| Density | 7850 kg/m³ |
| Yield (≤16mm) | ≥640 MPa |
| Yield (>16mm) | ≥660 MPa |
| Tensile (≤16mm) | ≥800 MPa |
| Tensile (>16mm) | ≥830 MPa |
| Elongation | ≥12 % |
| Young's E | 210 GPa |
| Hardness | 22–32 HRC |
| CTE | ~12 µm/m·K |
| Thermal cond. | ~45 W/m·K |
| Max service | ~300 °C (strength derates; not for creep duty) |
| Poisson ν | ~0.29 |
| Shear modulus G | ~81 GPa (derived) |
| Specific heat | ~460–480 J/kg·K |
| Elec. resistivity | ~0.15–0.25 µΩ·m (steel-dependent) |
| Melting range | ~1420–1500 °C |
| Fatigue (indicative) | — (bolt fatigue is thread-dominated — use VDI 2230 / EN 1993-1-9, not material values) |
Fasteners are bought finished — for turned specials use EN8/EN19 and heat treat to suit.
Never weld finished fasteners — Q&T properties are destroyed; use weld studs (ISO 13918) instead.
| System | Designation |
|---|---|
| EN | ISO 898-1 class 8.8 (EN ISO 4014/4017) |
| DIN | DIN 931/933 8.8 |
| ASTM | ≈SAE J429 Gr 5 / ASTM A449 (inch) |
| JIS | JIS B 1051 8.8 |
| BS | BS 3692 Gr 8.8 |
Equivalents & alternatives: ~SAE J429 Grade 5 (near); EN8/EN19 H&T for specials. Alt: 10.9 (higher preload), A2/A4-70 stainless (corrosion, lower strength).
High-strength class — preloaded structural assemblies (EN 14399/HSFG type) and high-duty machine fasteners.
Fastener steelThe socket-screw class — highest standard property class. Alloy steel, tightly controlled Q&T; usually self-colour/black.
