4140 is a chromium-molybdenum alloy steel commonly supplied pre-hardened (PHT, ~28-32 HRC). It machines reasonably well in this state and reaches ~50 HRC after heat treatment. Standard for high-strength fasteners, shafts, gears, and fixtures.
Mechanical and physical properties
| Property | Value (PHT) |
|---|---|
| Tensile strength | 950 MPa |
| Yield strength | 830 MPa |
| Elongation at break | 13% |
| Density | 7.85 g/cm³ |
| Modulus | 205 GPa |
| Hardness | 28-32 HRC (PHT) |
| Machinability rating | Fair (PHT) / Good (annealed) |
Typical applications
- Shafts, axles, gears.
- Tooling and fixtures.
- High-strength fasteners.
- Mining and oilfield components.
Heat treat sequence
Machine in the annealed condition, heat treat to target hardness, then grind tight tolerances. Do not try to heat treat after final machining — it will distort.
Specifying it on Uretyco
- 1Pick 4140 from the dropdown
Pre-hardened or annealed available.
- 2Decide on heat treat
Skip for moderate strength; specify if hardness > 32 HRC.
- 3Specify post-HT operations
Grinding, finishing.
- 4Add coating if outdoor
Zinc plate or paint — 4140 rusts.
Related materials
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