31CrMoV9
1.8519THE standard nitriding steel — Cr-Mo-V combination optimized for gas nitriding. Vanadium refines grain and forms hard VN nitrides (surface >750 HV). Better core toughness than 31CrMo12 at similar strength. THE default choice when "nitriding steel" is specified without further detail. Used for crankshafts, gears, spindles, extrusion screws, and precision machine components.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇪🇺 | EN | Europe | 31CrMoV9 / 1.8519 | 1.8519 | 100% |
Sources: EN 10085
Chemical composition comparison (wt%)
Side-by-side: 31CrMoV9 (EN) (EN 10085) vs 31CrMoV9 / 1.8519 (EN) (EN 10085)
| Element | 31CrMoV9 (EN) | 31CrMoV9 / 1.8519 (EN) | Overlap |
|---|---|---|---|
| C | 0.27–0.34% | 0.27–0.34% | OK |
| Si | 0–0.4% | 0–0.4% | OK |
| Mn | 0.4–0.7% | 0.4–0.7% | OK |
| P | 0–0.025% | 0–0.025% | OK |
| S | 0–0.035% | 0–0.035% | OK |
| Cr | 2.3–2.7% | 2.3–2.7% | OK |
| Mo | 0.15–0.25% | 0.15–0.25% | OK |
| V | 0.1–0.2% | 0.1–0.2% | OK |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 800–1000 | MPa |
| Yield Strength | 600–750 | MPa |
| Elongation | 12–16 | % |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.85 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 850–880 °C | oil | — | Oil quench |
| tempering | 550–650 °C | air | — | Temper BEFORE nitriding |
| nitriding | 500–530 °C | ammonia atmosphere | 15-80 hours | Gas nitriding — surface >750 HV with VN precipitates |
Compatibility verdict
31CrMoV9 and 31CrMoV9 / 1.8519: 100% 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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