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Alloy Steel

Alloy Steel 4140 (Chromium-Molybdenum)

4140 is a medium-carbon chromium-molybdenum alloy steel with good toughness, fatigue strength, and wear resistance. It can be through-hardened and is commonly supplied annealed or pre-hardened. Request a quote or browse all materials.

Typical Properties

Steel 4140 at a glance

PropertyTypical value
Density7.85 g/cm³ (0.284 lb/in³)
UTS, annealed~655 MPa (95 ksi)
Yield, annealed~415 MPa (60 ksi)
Elongation, annealed~25%
Hardness, annealed~197 HB
Pre-hardened (typical)~28–32 HRC
Elastic modulus~205 GPa
Thermal conductivity~42.6 W/m·K

Strength and hardness depend strongly on heat treatment; quench and temper can reach much higher hardness. Specify condition on the drawing. These are typical reference values from standard published data, not guaranteed minimums. Request material certificates in your RFQ if properties must be verified.

Advantages

Why engineers choose Steel 4140

Toughness

Good impact and fatigue resistance.

Hardenability

Through-hardens in moderate sections.

Wear

Suitable for gears, shafts, and tooling with heat treatment.

Availability

Common bar and plate stock, often pre-hardened.

Design considerations: Rusts without coating; welding requires preheat and post-weld treatment; harder conditions machine more slowly.

Applications

Common uses

Shafts and axlesGears and sprocketsTooling and fixturesSpindlesHeavy-duty fasteners

Processes and Finishes

How 3DWK can make it

Black Oxide

A common finish option for Steel 4140 parts.

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Plating & Conversion Coatings

A common finish option for Steel 4140 parts.

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Powder Coating

A common finish option for Steel 4140 parts.

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Alternatives

Related materials

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