AISI 4140 steel is a chromium-molybdenum alloy steel valued for its strength, toughness, wear resistance, and hardenability. It is commonly used for shafts, gears, machinery components, automotive parts, and other applications requiring reliable mechanical performance.
The 4140 steel properties depend on its chemical composition, product size, and delivery condition. Annealed 4140 is generally easier to machine, while quenched-and-tempered 4140 offers higher strength and hardness for demanding applications.
This guide covers 4140 steel composition, mechanical properties, hardness, density, and equivalent grades, with practical reference data to help buyers compare material specifications before ordering.
4140 Steel Properties Overview
The following table summarizes key 4140 steel material properties and common specification details.
| Property | Typical Reference |
|---|---|
| Steel Grade | AISI / SAE 4140 |
| UNS Designation | G41400 |
| Steel Type | Chromium-molybdenum alloy steel |
| Density of 4140 Steel | Approx. 7.85 g/cm³ |
| Elastic Modulus | Approx. 205 GPa |
| Common Product Forms | Bars, tubes, and other specified forms |
| Common Delivery Conditions | Annealed, normalized, quenched and tempered |
These 4140 steel specs are general reference information. Actual properties depend on product dimensions, manufacturing route, heat treatment, and the applicable material standard.
4140 Steel Composition
4140 steel composition determines many of its strength, hardenability, and toughness characteristics. The following are common chemical composition ranges for AISI/SAE 4140 steel.
| Element | Composition (wt.%) |
|---|---|
| Carbon (C) | 0.38–0.43% |
| Manganese (Mn) | 0.75–1.00% |
| Silicon (Si) | 0.15–0.35% |
| Chromium (Cr) | 0.80–1.10% |
| Molybdenum (Mo) | 0.15–0.25% |
| Phosphorus (P) | ≤ 0.035% |
| Sulfur (S) | ≤ 0.040% |
Carbon contributes to strength and hardness, while chromium and molybdenum improve hardenability and help the steel achieve suitable mechanical properties through heat treatment. Although 4140 contains chromium, it is a low-alloy steel, not stainless steel.
4140 Steel Mechanical Properties
The mechanical properties of 4140 steel vary with heat treatment, section size, and delivery condition. The values below are representative references rather than guaranteed minimums for every supplied product.
| Mechanical Property | Annealed Condition | Pre-hardened Condition |
|---|---|---|
| Yield Strength | Approx. 415 MPa | Approx. 690–760 MPa |
| Tensile Strength | Approx. 655 MPa | Approx. 930–1,000 MPa |
| Elongation | Approx. 25% | Approx. 16% |
| Hardness | Approx. 197 HBW | Commonly 28–32 HRC |
4140 steel yield strength and tensile strength are especially important when selecting material for load-bearing machine parts. The required values should be checked against the applicable specification, product size, and heat-treated condition.
4140 Steel Hardness and Density
4140 steel hardness depends largely on its heat treatment. Annealed material is commonly around 197 HBW, while pre-hardened material is often supplied at approximately 28–32 HRC. The required hardness should be specified when ordering, and values on different hardness scales should only be compared using an appropriate conversion standard.
The density of 4140 steel is approximately 7.85 g/cm³, a useful reference for estimating material weight and transport requirements. Density is generally less affected by the delivery condition than hardness and strength.
4140 Steel Equivalent Grades
When sourcing 4140 alloy steel, buyers may encounter equivalent or comparable grades in different national standards.
| Grade | Standard System |
|---|---|
| AISI / SAE 4140 | United States |
| 42CrMo4 | Europe |
| 42CrMo | China |
| SCM440 | Japan |
These grades have similar alloy-steel characteristics, but they are not automatically interchangeable. Chemical composition limits, mechanical property requirements, heat treatment, and applicable standards may differ. Confirm the required standard and material certificate before approving a substitute.
How to Source 4140 Steel
Before requesting a quotation, confirm:
- Grade and standard: AISI/SAE 4140 or an approved equivalent.
- Product form and dimensions: Bar, tube, or another required form, with specified sizes and tolerances.
- Delivery condition: Annealed, normalized, or quenched and tempered, as required.
- Quantity and documentation: Required quantity, material certificate, and inspection requirements.
For available supply options, specifications, and product forms, explore our 4140 steel range, including 4140 steel bar, 4140 steel tube, and 4140 steel plate. Providing dimensions, quantity, delivery condition, and destination helps clarify your requirements for a quotation.