Material datasheet · Low-alloy steel
AISI 4140 Cr-Mo Alloy Steel
UNS G41400 · Quenched & tempered (commonly delivered Q&T at 28-32 HRC)
The bread-and-butter alloy steel. Strong, tough, hardenable, cheap.
Chemical composition
Nominal % by weight.
| Element | % by wt |
|---|---|
| Fe | Bal. |
| C | 0.38–0.43 |
| Cr | 0.80–1.10 |
| Mo | 0.15–0.25 |
| Mn | 0.75–1.00 |
Applicable specifications
AMS / ASTM / MIL.
- AMS 6382 (annealed bar)
- AMS 6349
- ASTM A29
- ASTM A322
Austenitize 1550°F, oil quench, temper 1100–1200°F to target hardness.
Machining guidance
CNC parameters and tooling.
TiAlN-coated carbide; positive rake for Q&T condition
Pre-hard (28-32 HRC) machines reasonably; harder tempers require slower speeds and rigid setups.
Stock & cost
Forms and Q1 2026 pricing.
- Black oxide (MIL-DTL-13924)
- Phosphate (MIL-DTL-16232)
- Hard chrome plate
- Nickel plate
- Paint
Typical applications
Where 4140 Steel is the right pick.
- Drive shafts
- Hydraulic cylinders
- Gears
- Industrial fixtures
- Firearms components
Alternative materials
Substitute or upgrade options.
- 4340 (higher strength)
- 1045 (cheaper, lower hardenability)
- 17-4PH (no plating needed)
Digital Machine · Quick-Turn CNC · California
Machine your part in 4140 Steel.
Production CNC milling and turning. Confirm material, inspection and documentation requirements when requesting a quote.
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Related tools & references
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