Metals & alloys · Ferrous alloys
AISI 4140 / 42CrMo4-type steel
A chromium–molybdenum through-hardening steel used where strength, toughness, fatigue resistance and heat-treat response must be balanced.
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01
Overview
- Material class
- Metals & alloys
- Category
- Ferrous alloys
- Family
- Carbon & Low-Alloy Steel
- Product forms
- Sheet/plate, Bar/rod
Composition
| Constituent | Min | Max | Typical | Note |
|---|---|---|---|---|
| C | 0.38 | 0.43 | 0.4 | |
| Mn | 0.75 | 1 | 0.85 | |
| Si | 0.15 | 0.35 | 0.25 | |
| Cr | 0.8 | 1.1 | 0.95 | |
| Mo | 0.15 | 0.25 | 0.2 | |
| P | 0.035 | |||
| S | 0.04 | |||
| Fe | Balance |
02
Properties and conditions
Engineering properties
| Property | Value | Unit | Condition |
|---|---|---|---|
| Density | 7.85 | g/cm³ | Representative; verify product form and condition |
| Elastic modulus | 205 | GPa | Representative; verify product form and condition |
| Thermal conductivity | 42–46 | W/m·K | Representative; verify product form and condition |
| Yield strength | 655–930 | MPa | quenched and tempered; section dependent |
| Tensile strength | 850–1080 | MPa | quenched and tempered |
| Elongation | 10–18 | % | quenched and tempered |
Conditions
Annealed
Softened condition for machining or forming.
Normalized
Air-cooled normalized condition.
Quenched and tempered — higher temper
Lower-strength, higher-toughness quenched-and-tempered condition.
Quenched and tempered — lower temper
Higher-strength quenched-and-tempered condition; section size and tempering temperature required.
03
Processing and use
Processing
- Preheat and controlled cooling are normally required for welding.
- Quench severity and section size control through-hardening and distortion.
- Tempering establishes the final strength–toughness balance.
Applications
- Shafts and axles
- Gears and fasteners
- Oil-and-gas components
- High-strength machine parts
Selection considerations
- Avoid treating a nominal designation as a guaranteed property set.
- Check hardenability, cleanliness and ultrasonic quality for critical sections.
Open in an analysis tool
04
Standards and related materials
Standards and designations
| System | Designation | Note |
|---|---|---|
| SAE/AISI | 4140 | |
| UNS | G41400 | |
| EN | 1.7225 / 42CrMo4 | near-equivalent; verify chemistry and product standard |
| ASTM | A29/A322/A829 | depending product form |
05
Sources and context
Sources
- Atlas 4140 data sheetExisting reference
- SAE 4140 composition referenceExisting reference
- U.S. Department of Energy lightweight materials programApplication reference
Confirm the applicable specification, product form and condition before using values for design or procurement.
Supply and sustainability
Widely available as bar, plate, forging stock and tube; product quality levels vary by specification.
Strong recyclability; life extension through repair and re-heat-treatment can be valuable for large components.
Strategic context
Established engineering material with documented processing–performance relationships.