4620 Steel
A Ni-Mo carburizing alloy steel
Typical values for the temper in the title
4620 is a low-carbon (about 0.2%) steel with about 1.8% nickel and molybdenum, without chromium. It is intended for carburizing: a very hard surface, and a ductile, tough core thanks to the nickel.
It is used for gears, bearings and shafts under shock loads. It is often confused with 8620, but the composition differs: 8620 has chromium, 4620 does not.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 520 MPa | |
| Yield strength Rp0.2 | 365 MPa | |
| Elongation A | 22% | |
| Hardness | 149 HB | |
| Modulus of elasticity E | 207 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 65% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | 0.17–0.22 | low: a ductile core |
| Ni nickel | 1.65–2.00 | toughness and hardenability |
| Mo molybdenum | 0.20–0.30 | hardenability |
| Mn manganese | 0.45–0.65 | |
| Si silicon | 0.15–0.35 | |
| Fe iron | balance |
Ranges per SAE J404 and ASTM A322. P max 0.035, S max 0.040. Equivalents in other standards are close in composition, not identical.
Conditions and heat treatment
In alloy steels, chromium, molybdenum and nickel raise hardenability: thicker parts reach full hardness even at the center. Properties are set mainly by heat treatment.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed / hot rolled | for machining | delivery condition |
| Carburized | very hard surface, strong and tough core | gears, shafts and cams |
| Quenched and tempered (no carburizing) | medium strength | parts that do not need a hard surface |
Applications
- Gears
- Bearings
- Shafts under shock loads
- Cams and pins
- Transmission parts
Fabrication
Carburizing
Gives a hard case with a very ductile core thanks to the nickel.
Welding
Possible before carburizing.
Machining
Good hot rolled or annealed.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 8620 | 530–620 / 385–415 MPa | Good | with chromium and less nickel: the most common carburizing steel · material page |
| 9310 | 1035–1380 / 795–1100 MPa | Good | more nickel, for aerospace · material page |
| 1018 | 400 / 220 MPa | Excellent | a cheap carbon steel for carburizing · material page |
Common mistakes
Replacing 4620 with 8620 without checking
The composition differs, and so does core toughness.
Trying to through-harden it
Too little carbon. Carburize.
Relying on equivalents found in sources
Many equivalents listed for 4620 actually belong to 8620. Check the composition.
Equivalents, standards and supply
| Standards | ASTM A29 / ASTM A322 |
|---|---|
| Forms | rod · wire · forging |
| Producers | TimkenSteel · Nucor · Gerdau |
Learn more
Values are typical and for comparison only, and depend strongly on condition and diameter. For design, rely on the standard and on the mill certificate. Sources: SAE J403 and J404, ASTM A29, A322 and A519 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026