18CrNiMo7-6
1.6587Premium Cr-Ni-Mo case-hardening steel for the most demanding gear applications. Excellent core toughness and hardenability for large cross-sections. The standard gear steel for wind turbines, heavy-duty gearboxes, and aerospace gearing.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | AISI 4820 (approx) | — | REF |
| 🇪🇺 | EN | Europe | 18CrNiMo7-6 | 1.6587 | 100% |
| 🇨🇳 | GB | China | 17CrNiMo6 | — | 90% |
Sources: ASTM A29, EN 10084:2008, GB/T 3077
Chemical composition comparison (wt%)
Side-by-side: 18CrNiMo7-6 (EN) (EN 10084:2008) vs 17CrNiMo6 (GB)
| Element | 18CrNiMo7-6 (EN) | 17CrNiMo6 (GB) | Overlap |
|---|---|---|---|
| C | 0.15–0.21% | — | — |
| Si | 0–0.4% | — | — |
| Mn | 0.5–0.9% | — | — |
| P | 0–0.025% | — | — |
| S | 0–0.035% | — | — |
| Cr | 1.5–1.8% | — | — |
| Mo | 0.25–0.35% | — | — |
| Ni | 1.4–1.7% | — | — |
Mechanical properties
Carburized QT
| Property | Value | Unit |
|---|---|---|
| Hardness HRC | 58–62 | HRC |
| Tensile Strength | 1050–1350 | MPa |
As Received
| Property | Value | Unit |
|---|---|---|
| Hardness HB | ≤ 229 | HB |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.85 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| carburizing | 880–950 °C | — | Depends on case depth | Gas carburizing typical. Case depth 1.0-3.0mm for large gears |
| quenching | 810–840 °C | oil | min 30 min | Direct quench or reheat |
| tempering | 150–200 °C | air | 120 min minimum | Low-temperature temper |
| annealing | 640–680 °C | furnace | Several hours | Soft annealing |
Compatibility verdict
18CrNiMo7-6 and 17CrNiMo6: 90% 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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