8620 / 20NiCrMo2-2
1.6523Nickel-chromium-molybdenum case-hardening steel. Good combination of core toughness and case hardness. The most widely used case-hardening steel in the US (AISI 8620). Used for gears, pinions, worm drives, king pins, and cross-shafts.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | AISI 8620 | G86200 | REF |
| 🇪🇺 | EN | Europe | 20NiCrMo2-2 | 1.6523 | 100% |
| 🇨🇳 | GB | China | 20CrNiMo | — | 90% |
| 🇯🇵 | JIS | Japan | SNCM220 | — | 88% |
Sources: ASTM A29, EN 10084:2008, GB/T 3077, JIS G4103
Chemical composition comparison (wt%)
Side-by-side: 8620 / 20NiCrMo2-2 (EN) (EN 10084:2008) vs AISI 8620 (AISI) (ASTM A29)
| Element | 8620 / 20NiCrMo2-2 (EN) | AISI 8620 (AISI) | Overlap |
|---|---|---|---|
| C | 0.17–0.23% | 0.18–0.23% | OK |
| Si | 0–0.4% | — | — |
| Mn | 0.65–0.95% | 0.7–0.9% | OK |
| P | 0–0.025% | 0–0.035% | OK |
| S | 0–0.035% | 0–0.04% | OK |
| Cr | 0.3–0.65% | 0.4–0.6% | OK |
| Mo | 0.15–0.25% | 0.15–0.25% | OK |
| Ni | 0.4–0.7% | 0.4–0.7% | OK |
Mechanical properties
Carburized QT
| Property | Value | Unit |
|---|---|---|
| Hardness HRC | 58–62 | HRC |
| Tensile Strength | 800–1100 | MPa |
As Received
| Property | Value | Unit |
|---|---|---|
| Hardness HB | ≤ 212 | HB |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.85 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| carburizing | 880–930 °C | — | Depends on case depth | Typical case depth 0.5-1.5mm |
| quenching | 810–840 °C | oil | min 30 min | Direct quench or reheat |
| tempering | 150–200 °C | air | 60-120 min | Low-temperature temper |
| annealing | 640–680 °C | furnace | Several hours | Soft annealing |
Compatibility verdict
8620 / 20NiCrMo2-2 and AISI 8620: 93% composition match
Close equivalents but NOT identical. Critical differences: C range (0.17–0.23 vs 0.18–0.23), Mn range (0.65–0.95 vs 0.7–0.9), P range (0–0.025 vs 0–0.035), S range (0–0.035 vs 0–0.04).
For dual certification, melt must hit: C 0.18–0.23, Mn 0.7–0.9, P 0–0.025, S 0–0.035
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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