EN8 and EN9 are the two workhorse plain carbon steels of UK engineering. The step from 0.40% carbon (EN8) to 0.55% carbon (EN9) buys strength, hardness and wear resistance — and costs ductility, toughness and weldability. Choosing between them comes down to one question: is the part's main enemy load, or wear?
| Property | EN8 (080M40 / C40E) | EN9 (070M55 / C55E) |
|---|---|---|
| Carbon content | 0.36–0.44% | 0.50–0.60% |
| Classification | Medium carbon | High carbon |
| Tensile strength (normalised, ≤16mm) | 550–700 N/mm² | 620–770 N/mm² |
| Yield strength (normalised, ≤16mm) | ~340 N/mm² | ~370 N/mm² |
| Elongation (normalised) | ~14% | ~10% |
| Toughness / ductility | Better | Lower — higher carbon |
| Wear resistance | Moderate | Good — the reason to specify EN9 |
| Flame/induction hardening response | ~50–55 HRC surface | Higher achievable surface hardness |
| Weldability | Fair — with care | Poor — generally avoid welding |
| Machinability | Good | Fair |
| Typical applications | Shafts, axles, studs, keys, general machined parts | Blades, springs, wear strips, agricultural tooling |
| DIN / EN equivalent | C40E / 1.1186 | C55E / 1.1203 |
| Stocked bright & black | Yes | Yes |
| 3.1 cert available | Yes | Yes |
Carbon is the cheapest strengthening element in steel, and the step from EN8 to EN9 is purely a carbon step — neither grade carries deliberate alloy additions. More carbon means more pearlite in the structure: harder, stronger, more wear-resistant, but less ductile and markedly less friendly to welding.
Both grades respond well to surface hardening, but EN9's higher carbon reaches a higher surface hardness, which is why it dominates agricultural wear parts and cutting edges. If you need substantially more core strength than either grade offers, the next step is an alloy steel — see EN8 vs EN19.
EN8 and EN9 bright and black bar from stock at Sherwood Park. Cut to length from one piece. 3.1 certs available on both.