EN18 is a medium-carbon chromium steel with about 0.4% carbon and 1% chromium. It hardens well in oil and, hardened and tempered, gives good strength and toughness for shafts, axles, gears, studs and bolts that need more than EN8 but less than EN19 or EN24. It can also be induction hardened for a wear-resistant surface.
Quick facts
- Type
- Medium-carbon chromium alloy steel
- Carbon
- About 0.35–0.45%
- Chromium
- About 0.85–1.15%
- Tensile strength
- About 700–1,000 MPa hardened and tempered
- Hardening
- Oil quench from about 830–860 °C
- Machinability
- Fair; best in the annealed or tempered state
Equivalent grades
| Standard | Grade |
|---|---|
| BS 970 | EN18 / 530M40 |
| EN / DIN | 41Cr4 (1.7035) |
| SAE / AISI | 5140 |
| IS | 40Cr4 |
Equivalents are close, not identical. Name the grade and standard on the drawing.
Typical chemical composition
| Element | % |
|---|---|
| Carbon (C) | About 0.35–0.45 |
| Chromium (Cr) | About 0.85–1.15 |
| Manganese (Mn) | About 0.6–0.9 |
| Silicon (Si) | About 0.1–0.35 |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
Typical uses
- Shafts, axles and spindles
- Gears and pinions
- Studs, bolts and connecting parts
- Induction-hardened pins and rollers
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Questions
- EN18 or EN19?
- EN19 has molybdenum and hardens deeper, so it is chosen for larger and more heavily loaded parts. EN18 is a little cheaper and enough for medium sections.
- Can EN18 be induction hardened?
- Yes, it responds well and is often induction hardened on shafts and pins for a hard surface over a tough core.
- What is the Indian equivalent of EN18?
- 40Cr4 in IS 1570.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.