The socket-screw class — highest standard property class. Alloy steel, tightly controlled Q&T; usually self-colour/black.
| Property | Typical value |
|---|---|
| Density | 7850 kg/m³ |
| Yield | ≥1100 MPa |
| Tensile | ≥1220 MPa |
| Elongation | ≥8 % |
| Young's E | 210 GPa |
| Hardness | 39–44 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) |
Bought finished.
Never weld. Significant hydrogen-embrittlement risk — avoid electroplating and hot-dip galvanising.
| System | Designation |
|---|---|
| EN | ISO 898-1 class 12.9 (EN ISO 4762 socket screws) |
| DIN | DIN 912 12.9 |
| ASTM | ≈ASTM A574 (alloy socket screws) / ≈SAE J429 Gr 8+ |
| JIS | JIS B 1051 12.9 / B 1176 |
| BS | BS 3692 Gr 12.9 |
Equivalents & alternatives: ~SAE ≈ Grade 8+ ; typically 34CrMo4-class steel. Alt: 10.9 where coatings are needed.
The standard high-tensile bolt class — general structural and machine fasteners. Medium-carbon (or boron) steel, quenched & tempered.
Fastener steelHigh-strength class — preloaded structural assemblies (EN 14399/HSFG type) and high-duty machine fasteners.
