Overview
SAE/AISI 5140 Steel is a chromium alloy steel containing approximately 0.38–0.43% carbon and 0.70–0.90% chromium, offering an excellent combination of strength, toughness, wear resistance, hardenability, and fatigue resistance.
Compared with carbon steel grades such as 1045, SAE 5140 provides superior hardenability and wear resistance due to its chromium content. Compared with SAE 4140, it offers slightly lower strength but improved cost-effectiveness for many industrial applications.
SAE 5140 is widely used in:
- Automotive Components
- Gears & Pinions
- Shafts & Axles
- Construction Machinery
- Agricultural Equipment
- Forged Components
- Hydraulic Systems
- Industrial Machinery
Because of its balance between performance and cost, 5140 is commonly selected for medium-to-heavy-duty mechanical components.
Material Specification
| Property | Value |
|---|---|
| Material Designation | SAE/AISI 5140 |
| Standard | ASTM A29 / SAE J404 |
| UNS Number | G51400 |
| Material Family | Chromium Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Standard Forms | Bar, Plate, Forgings, Tube, Shafting |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.38–0.43 |
| Chromium (Cr) | 0.70–0.90 |
| Manganese (Mn) | 0.70–0.90 |
| Silicon (Si) | 0.15–0.35 |
| Phosphorus (P) | ≤0.035 |
| Sulfur (S) | ≤0.040 |
Chromium significantly improves hardenability, wear resistance, and fatigue performance compared with plain carbon steels.
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 620–760 MPa |
| Yield Strength | 380–520 MPa |
| Elongation | 18–25% |
| Hardness | 180–220 HB |
| Elastic Modulus | 205 GPa |
Quenched & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 850–1100 MPa |
| Yield Strength | 650–900 MPa |
| Elongation | 12–18% |
| Hardness | 28–40 HRC |
Induction Hardened Condition
| Property | Value |
|---|---|
| Surface Hardness | 52–60 HRC |
| Core Toughness | Excellent |
| Wear Resistance | Outstanding |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1510°C |
| Thermal Conductivity | 44 W/m·K |
| Electrical Resistivity | 0.20 μΩ·m |
| Thermal Expansion Coefficient | 11.5 × 10⁻⁶/K |
| Specific Heat Capacity | 475 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Good |
| Dry Atmosphere | Good |
| Outdoor Environment | Moderate |
| Humid Environment | Moderate |
| Marine Environment | Poor |
| Chemical Environment | Poor |
Although better than plain carbon steel, SAE 5140 is not considered corrosion resistant.
Recommended surface treatments:
- Black Oxide
- Zinc Plating
- Nickel Plating
- Hard Chrome Plating
- Phosphate Coating
- QPQ Treatment
- Powder Coating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Good |
| MIG Welding | Good |
| Arc Welding | Good |
| Resistance Welding | Moderate |
| Spot Welding | Moderate |
For thick sections:
- Preheating Recommended
- Post-Weld Stress Relief Recommended
5140 welds more easily than higher-alloy grades such as 4340.
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Drilling | Good |
| Grinding | Excellent |
| Threading | Good |
| Broaching | Good |
Machinability Comparison
| Material | Machinability |
|---|---|
| 1045 | Good–Excellent |
| 5140 | Good |
| 4140 | Good |
| 4340 | Moderate |
| 8620 | Good |
5140 machines well in the annealed and pre-hardened conditions.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 815–870°C |
| Cooling Method | Furnace Cool |
Normalizing
| Parameter | Value |
|---|---|
| Temperature | 850–900°C |
| Cooling Method | Air Cool |
Quenching
| Parameter | Value |
|---|---|
| Temperature | 830–860°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 200–650°C |
| Purpose | Strength & Toughness Adjustment |
Induction Hardening
| Property | Value |
|---|---|
| Surface Hardness | 52–60 HRC |
| Hardened Depth | 1–8 mm |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| SAE/AISI (USA) | 5140 |
| ASTM (USA) | ASTM A29 Grade 5140 |
| UNS | G51400 |
| GB/T (China) | 40Cr |
| EN (Europe) | 41Cr4 |
| DIN (Germany) | 1.7035 / 41Cr4 |
| JIS (Japan) | SCr440 |
| ISO | 41Cr4 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Alloy Plate | Yes |
| Forgings | Yes |
| Mechanical Tube | Yes |
| Seamless Pipe | Yes |
| Ground Shafting | Yes |
| Pre-Hardened Bar | Yes |
Typical Applications
Automotive Industry
- Axles
- Drive Shafts
- Steering Components
- Transmission Components
Gear Manufacturing
- Spur Gears
- Helical Gears
- Pinions
- Gear Shafts
Construction Machinery
- Excavator Pins
- Loader Components
- Hydraulic Parts
- Structural Components
Agricultural Equipment
- PTO Shafts
- Drive Components
- Gear Systems
- Wear Parts
Industrial Machinery
- Rollers
- Couplings
- Mechanical Assemblies
- Power Transmission Parts
Hydraulic Industry
- Hydraulic Rods
- Cylinder Components
- Valve Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Heat Treatment | Outstanding |
| Induction Hardening | Outstanding |
| Forging | Excellent |
| Grinding | Excellent |
| Hard Chrome Plating | Excellent |
| QPQ Treatment | Excellent |
Advantages
Good Strength-to-Cost Ratio
Excellent performance at a lower cost than 4140 and 4340.
Good Hardenability
Provides deep and uniform hardening.
Excellent Wear Resistance
Especially after induction hardening.
Good Fatigue Resistance
Suitable for dynamic loading applications.
Good Toughness
Handles impact and shock loads well.
Widely Available
Commonly stocked globally.
Limitations
Lower Strength Than 4140
Not suitable for ultra-high-strength applications.
Limited Corrosion Resistance
Requires protective coatings.
Welding Requires Precautions
Preheating may be necessary.
Lower Toughness Than 4340
Not recommended for extreme aerospace applications.
Comparison with Other Alloy Steels
| Property | 5140 | 40Cr | 4140 | 4340 | 1045 |
|---|---|---|---|---|---|
| Carbon Content | 0.40% | 0.40% | 0.40% | 0.40% | 0.45% |
| Chromium Content | Medium | Medium | Higher Alloy | Higher Alloy | None |
| Strength | High | High | Very High | Exceptional | Medium |
| Hardenability | Good | Good | Excellent | Outstanding | Moderate |
| Cost | Medium | Medium | Higher | Highest | Low |
Comparison with Engineering Materials
| Material | Yield Strength | Hardness Potential | Fatigue Resistance |
|---|---|---|---|
| SAE 5140 | 650–900 MPa | 60 HRC | Excellent |
| 40Cr | 650–900 MPa | 60 HRC | Excellent |
| SAE 4140 | 655–1200 MPa | 58 HRC | Excellent |
| SAE 4340 | 740–1600 MPa | 60 HRC | Outstanding |
| 1045 Steel | 550–700 MPa | 58 HRC | Good |
| 17-4PH Stainless | 860–1170 MPa | 44 HRC | Excellent |
Available Surface Finishes
Raw Finishes
- Annealed Finish
- Normalized Finish
- Quenched & Tempered Finish
- Pre-Hardened Finish
Protective Finishes
- Black Oxide
- Zinc Plating
- Nickel Plating
- Hard Chrome Plating
- QPQ Treatment
- Phosphate Coating
Decorative Finishes
- Powder Coating
- Spray Painting
- Electrophoretic Coating (E-Coating)
Frequently Asked Questions (FAQ)
What is SAE 5140 steel?
SAE 5140 is a chromium alloy steel known for its good strength, wear resistance, hardenability, and fatigue performance.
What is SAE 5140 used for?
Typical applications include:
- Gears
- Shafts
- Axles
- Hydraulic Components
- Agricultural Equipment
- Industrial Machinery
What is the difference between SAE 5140 and SAE 4140?
| Property | SAE 5140 | SAE 4140 |
|---|---|---|
| Alloy Elements | Chromium Only | Chromium + Molybdenum |
| Strength | High | Higher |
| Hardenability | Good | Better |
| Cost | Lower | Higher |
What is the difference between SAE 5140 and 40Cr?
SAE 5140 and Chinese 40Cr are generally considered equivalent grades and are interchangeable in most industrial applications.
Can SAE 5140 be induction hardened?
Yes. Surface hardness can reach 52–60 HRC after induction hardening.
Is SAE 5140 suitable for gears?
Yes. It is widely used for medium-to-heavy-duty gears, shafts, and pinions.
Can SAE 5140 be welded?
Yes. Proper preheating and stress relief are recommended for critical applications.
What hardness can SAE 5140 achieve?
- Quenched & Tempered: 28–40 HRC
- Induction Hardened: 52–60 HRC
Why is SAE 5140 widely used in machinery manufacturing?
Because it combines:
- Good Strength
- Good Hardenability
- Excellent Wear Resistance
- Cost Efficiency
- Reliable Fatigue Performance
making it ideal for industrial power transmission components.
Does GCNOV provide custom manufacturing services for SAE 5140?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Gear Manufacturing
- Shaft Machining
- Induction Hardening
- QPQ Treatment
- Heat Treatment
- Precision Grinding
- Hard Chrome Plating
- Prototype Development
- Low-Volume Production
- Mass Production