EN8 vs EN19
EN8 and EN19 sit either side of the most common material decision in Indian engineering. The honest dividing line is not strength on paper — it is section size, because that is where EN8 quietly fails to deliver what its certificate promises.
EN8 is a medium carbon steel; EN19 adds chromium and molybdenum for hardenability. Both reach similar surface hardness, but EN19 develops uniform properties through thick sections where EN8 leaves a soft core. Above roughly 60 mm section, or wherever fatigue governs, choose EN19.
- Carbon (both)
- ≈0.36 – 0.44%
- EN19 adds
- 0.9–1.2% Cr, 0.15–0.3% Mo
- EN8 tensile
- 620 – 700 MPa normalised
- EN19 tensile
- 850 – 1000 MPa Q&T
- Switch point
- ≈60 mm section
- Relative cost
- EN19 roughly 25–40% higher
Key takeaways
- The decision is about section size and hardenability, not headline tensile strength.
- EN8 in a 100 mm section leaves a soft core no coupon test will show.
- If only a surface wears, induction harden EN8 rather than paying for EN19 throughout.
- Over-specifying EN19 costs money and machinability without improving what governs the design.
EN8 vs EN19 at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Carbon (both): ≈0.36 – 0.44%
- EN19 adds: 0.9–1.2% Cr, 0.15–0.3% Mo
- EN8 tensile: 620 – 700 MPa normalised
- EN19 tensile: 850 – 1000 MPa Q&T
- Switch point: ≈60 mm section
- Relative cost: EN19 roughly 25–40% higher
| Factor | EN8 (080M40) | EN19 (42CrMo4) |
|---|---|---|
| Alloying | None deliberate | Chromium + molybdenum |
| Hardenability | Shallow, surface only | Deep, through-section |
| Tensile strength | 620–700 MPa normalised | 850–1000 MPa quenched & tempered |
| Best section size | Up to ~60 mm | 60 mm and above |
| Machinability | Better | Harder on tooling |
| Relative cost | Baseline | 25–40% higher |
| Choose it for | Brackets, pins, light shafts | Crankshafts, axles, loaded gears |
The Real Difference Is Hardenability
Both hold roughly 0.4% carbon, so both can be hardened at the surface. EN19 adds chromium and molybdenum, which lets hardening penetrate deep into a thick section. In a 100 mm shaft, EN8 hardens only in an outer skin while the core stays soft — a difference no tensile test on a small coupon will reveal.
- Similar carbon, very different hardenability
- EN8 hardens shallow, EN19 deep
- Core properties diverge above ~60 mm
- Coupon testing can hide the difference
Cost and Machinability
EN8 costs meaningfully less and machines more freely. On brackets, pins, light shafts and general machinery parts it is the correct answer, and specifying EN19 there simply raises cost and tool wear for no functional gain.
The Decision Rule We Use
Below 60 mm section with moderate load, EN8. Above 60 mm needing uniform properties, or wherever fatigue governs, EN19. If only a surface wears, keep EN8 and induction harden it rather than upgrading the whole part.
Topics covered on this page
- EN8 vs EN19
- EN8 or EN19 which is better
- difference between EN8 and EN19
- EN19 vs EN8 hardness
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
Is EN19 stronger than EN8?
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In thick sections decisively, because it hardens through. In thin sections properly heat treated, the gap narrows considerably.
Can I use EN8 instead of EN19 to save cost?
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On light, thin, non-fatigue parts yes. On thick or fatigue-loaded components the core will be soft and the substitution is unsafe.
Which machines better?
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EN8, noticeably. EN19 in the quenched and tempered condition is harder on tooling and slower to cut.
Which do you recommend for shafts?
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EN8 for light duty under 60 mm; EN19 for loaded shafts above that, or anywhere fatigue governs the design.