Medium-carbon steel — shafts, studs, gears, keys. Through-hardenable to moderate strength.
| Property | Typical value |
|---|---|
| Density | 7850 kg/m³ |
| Yield | ~465 MPa (cold drawn / Q&T); ≥280 MPa normalised |
| Tensile | 550–700 MPa |
| Elongation | ~16 % |
| Young's E | 210 GPa |
| Hardness | ~200–255 HB |
| CTE | ~12 µm/m·K |
| Thermal cond. | ~50 W/m·K |
| Hardened | ~50–55 HRC |
| Max service | ~400 °C |
| Poisson ν | ~0.29 |
| Shear modulus G | ~81 GPa (derived) |
| Shear strength | ≈0.6 × UTS (design convention — not test data) |
| Specific heat | ~460–480 J/kg·K |
| Elec. resistivity | ~0.17 µΩ·m |
| Melting range | ~1430–1510 °C |
| Fatigue (indicative) | ~250–350 MPa (≈0.45–0.5 × UTS) — rotating-bend, polished specimen; indicative only, surface/size/loading factors apply |
~55–60%. Machines well in normalised/‘T’ condition.
Preheat 150–260 °C and post-weld temper; risk of HAZ cracking.
| System | Designation |
|---|---|
| EN | C40E / 1.1186 (≈C45E / 1.1191, C45 / 1.0503) |
| DIN | Ck40 / Ck45 |
| AISI | 1040 (≈1045) |
| JIS | S40C / ≈S45C |
| BS | BS 970 080M40 (EN8) |
| UNS | G10400 (≈G10450) |
Equivalents & alternatives: 080M40 (EN8); 1.1186 (C45E); AISI 1040. Alt: EN8D (tighter), EN19/EN24 for higher duty.
General structural mild steel — sections, plate, weldments. The default for fabrication.
Carbon steelHigher-strength structural steel — same weldability as S275 with ~30% more yield.
Carbon steelFree-cutting bright mild steel — first choice for high-volume machined parts, studs, fittings.
Carbon steelGeneral bright mild steel bar — weldable, case-hardenable, good all-rounder for machined parts.
