39NiCrMo3
1.6510Nickel-chromium-molybdenum quench & temper steel. Similar to AISI 4340 but with lower Ni — more economical. Good hardenability for sections up to ~80mm. Excellent balance of strength, toughness, and fatigue resistance. High white-point sensitivity — hydrogen control required. Used for crankshafts, connecting rods, gear shafts, landing gear components, and heavy-duty machinery parts.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | AISI 9840 | — | REF |
| 🇪🇺 | EN | Europe | 39NiCrMo3 / 1.6510 | 1.6510 | 100% |
| 🇫🇷 | AFNOR | France | 40NCD3 | — | 95% |
Sources: ASTM A519, EN 10083-3, NF
Chemical composition comparison (wt%)
Side-by-side: 39NiCrMo3 (EN) (EN 10083-3) vs 40NCD3 (AFNOR)
| Element | 39NiCrMo3 (EN) | 40NCD3 (AFNOR) | Overlap |
|---|---|---|---|
| C | 0.35–0.43% | — | — |
| Si | 0–0.4% | — | — |
| Mn | 0.5–0.8% | — | — |
| P | 0–0.025% | — | — |
| S | 0–0.035% | — | — |
| Cr | 0.6–1% | — | — |
| Mo | 0.15–0.25% | — | — |
| Ni | 0.7–1% | — | — |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 900–1200 | MPa |
| Yield Strength | 600–800 | MPa |
| Elongation | 10–16 | % |
| Hardness HB | 260–340 | HB |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.85 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 830–860 °C | oil | — | Oil quench — water risks cracking due to Ni content |
| tempering | 540–660 °C | air | — | Temper to target strength class |
Compatibility verdict
39NiCrMo3 and 40NCD3: 95% composition match
Close equivalents but NOT identical.
Related materials
50CrV4
1.8160Chromium-vanadium spring/tool steel — identical alloy system to 51CrV4 (1.8159) but recognized as a separate grade in some standards. Dual use: heavy-duty springs (EN 10089) AND cold work tools (knives, shear blades). V improves temper resistance and grain refinement. UTS 1200-1500 QT. Used for heavy leaf springs, stabilizer bars, torsion bars, and cold work cutting tools.
51CrMoV4
1.7701CrMoV alloyed spring steel — THE European automotive suspension spring material. CrMo gives deep hardenability for large coil springs, V adds grain refinement and secondary hardening for fatigue resistance. UTS 1350-1600 MPa QT. Used for hot-formed coil springs (cars, trucks), leaf springs, torsion bars, and stabilizer bars. Excellent sag resistance to 200°C.
20MnCr5
1.7147Manganese-chromium case-hardening steel with higher core strength than 16MnCr5. Used for heavily loaded gears, shafts, camshafts, and transmission components requiring high surface hardness with tough core. Popular in automotive and heavy machinery.
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