4320
Data verified4320 is a Ni-Cr-Mo carburizing steel whose ~1.8% nickel gives a markedly tougher core than 8620. It is specified for larger, shock-loaded gears in mining, truck and industrial transmissions.
Chemical composition
| Element | Content (%) |
|---|---|
| C | 0.17–0.22 |
| Si | 0.15–0.35 |
| Mn | 0.45–0.65 |
| P | ≤0.035 |
| S | ≤0.040 |
| Cr | 0.40–0.60 |
| Ni | 1.65–2.00 |
| Mo | 0.20–0.30 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Case hardness (carburized) | 58–62 HRC |
| Core tensile strength | 750–1000 MPa (typ.) |
| Density | 7.85 g/cm³ |
Heat treatment
Carburize 900–930 °C; quench 800–830 °C oil; temper 150–200 °C.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 20NiCrMo2-2 family (near) |
| aisi | 4320 |
| jis | SNCM420 |
| gb | 20CrNiMo |
Compare side by side: 4320 vs 17CrNiMo6 · 4320 vs 8620
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Heavy gears and pinions, transmission shafts, mining equipment gears.
Processing: Machines well soft; nickel content makes case/core response forgiving over a wide section range.
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Ask for a quotationVisit NasteelSource: SAE J404 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.