9310 Steel
A Ni-Cr-Mo carburizing alloy steel, for aerospace
Typical values for the temper in the title
9310 contains about 3.2% nickel, about 1.2% chromium and a little molybdenum, with low carbon (0.07–0.13% per AMS 6260). The high nickel gives a core with very high toughness and fatigue resistance.
It is the classic choice for aerospace gears, especially in helicopter transmissions, where failure is not an option. It is produced in aircraft quality (sometimes vacuum remelted).
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 1035–1380 MPa | |
| Yield strength Rp0.2 | 795–1100 MPa | |
| Elongation A | 12% | |
| Hardness | 295–390 HB | |
| Modulus of elasticity E | 203 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 57% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Ni nickel | about 3.2 (nominal) | toughness and fatigue resistance |
| Cr chromium | about 1.2 (nominal) | hardenability |
| Mo molybdenum | about 0.12 (nominal) | hardenability |
| C carbon | 0.07–0.13 (AMS 6260) | low: a ductile core |
| Fe iron | balance |
Nominal composition per the AMS 6260 title. Exact ranges are in the specification and SAE J404. 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
- Helicopter transmission gears
- Aircraft engine gears
- Aerospace shafts
- Critical transmission parts
- Bearings
Fabrication
Carburizing
To strict aerospace specifications, with control of case depth, hardness and microstructure.
Quality
Supplied in aircraft quality, with strict cleanliness requirements.
Processing
Usually machined, carburized and ground.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 8620 | 530–620 / 385–415 MPa | Good | much cheaper, for industrial use · material page |
| 4620 | 520 / 365 MPa | Good | medium nickel, no chromium · material page |
| 4340 | 1080–1470 / 970–1380 MPa | Difficult — Preheat 200C | not for carburizing: for through-strength · material page |
Common mistakes
Replacing 9310 with 8620 in an aerospace part
Toughness and fatigue resistance differ greatly. The specification is binding.
Saving on process control
In aerospace gears, case depth and microstructure are inspected.
Ordering without aircraft quality
Cleanliness and inspection requirements differ.
Equivalents, standards and supply
| EN | 14NiCrMo13-4 (close) |
|---|---|
| DIN | 1.6657 |
| JIS | SNCM815 |
| Standards | ASTM A322 / AMS 6260 |
| Forms | rod · forging |
| Producers | Carpenter · TimkenSteel |
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