30CrNiMo8 vs 4340
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
30CrNiMo8
Alloy & Engineering Steel
30CrNiMo8 is a high-hardenability EN Q&T steel (1.6580) with about 2% each of chromium and nickel. It is specified for large, highly stressed parts — rotor shafts, aircraft components and heavy fasteners — where 42CrMo4 runs out of section capability.
Standards: DIN 1.6580 (30CrNiMo8)
4340
Alloy & Engineering Steel
4340 is a Ni-Cr-Mo steel with deep hardenability and high fatigue strength, used where 4140 runs out of section size or toughness: landing gear, large shafts and high-strength fasteners.
Standards: DIN 1.6511 (36CrNiMo4) · AISI 4340 · JIS SNCM439 · GB 40CrNiMo
Chemical composition compared (%)
| Element | 30CrNiMo8 | 4340 |
|---|---|---|
| C | 0.26–0.34 | 0.38–0.43 |
| Si | ≤0.40 | 0.15–0.35 |
| Mn | 0.50–0.80 | 0.60–0.80 |
| P | ≤0.025 | — |
| S | ≤0.035 | — |
| Cr | 1.80–2.20 | 0.70–0.90 |
| Ni | 1.80–2.20 | 1.65–2.00 |
| Mo | 0.30–0.50 | 0.20–0.30 |
Properties compared
| Property | 30CrNiMo8 | 4340 |
|---|---|---|
| Hardness (Q&T) | 34–44 HRC typical | 33–45 HRC typical |
| Tensile strength | 1100–1400 MPa (Q&T, EN 10083 section bands) | 1100–1400 MPa (Q&T) |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Hardenability | — | Very high (large sections) |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: 30CrNiMo8 · 4340. Substitution decisions for certified parts stay with the design authority.