31CrMo12
1.8515Deep nitriding steel with 3% Cr — the highest Cr content in the EN 10085 nitriding series. Produces the deepest and hardest nitrided case (surface hardness >900 HV, case depth >0.5mm). Core strength 800-1000 MPa QT. Used where maximum surface hardness and wear resistance with a tough core is needed: large gears, cylinder liners, spindles, precision measuring tools, and heavy-duty sliding components.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇪🇺 | EN | Europe | 31CrMo12 / 1.8515 | 1.8515 | 100% |
Sources: EN 10085
Chemical composition comparison (wt%)
Side-by-side: 31CrMo12 (EN) (EN 10085) vs 31CrMo12 / 1.8515 (EN) (EN 10085)
| Element | 31CrMo12 (EN) | 31CrMo12 / 1.8515 (EN) | Overlap |
|---|---|---|---|
| C | 0.28–0.35% | 0.28–0.35% | 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 | 2.8–3.3% | 2.8–3.3% | OK |
| Mo | 0.3–0.5% | 0.3–0.5% | 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 | 860–890 °C | oil | — | Oil quench |
| tempering | 580–680 °C | air | — | Temper BEFORE nitriding |
| nitriding | 500–530 °C | ammonia atmosphere | 20-90 hours | Gas nitriding — surface >900 HV, depth depends on time |
Compatibility verdict
31CrMo12 and 31CrMo12 / 1.8515: 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.
Not sure which material fits?
🤖 Ask AI Advisor →All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.