Overview
40Cr Steel is one of the most widely used medium-carbon chromium alloy steels in China. It offers an excellent combination of strength, toughness, wear resistance, hardenability, fatigue resistance, and machinability, making it a preferred material for shafts, gears, axles, molds, and mechanical transmission components.
Compared with 45# steel, 40Cr provides significantly better hardenability and mechanical properties after heat treatment. Compared with SAE 4140, 40Cr is generally considered a close equivalent and is widely used as a cost-effective engineering steel.
40Cr is commonly used in:
- Transmission Shafts
- Gears & Pinions
- Axles
- Hydraulic Components
- Machine Tool Parts
- Construction Machinery
- Automotive Components
- Mold Bases
Because of its versatility and reliable performance, 40Cr is one of the most popular engineering steels in manufacturing industries worldwide.
Material Specification
| Property | Value |
|---|---|
| Material Designation | 40Cr |
| Standard | GB/T 3077 |
| Material Family | Chromium Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Annealed, Normalized, Quenched & Tempered |
| Standard Forms | Bar, Plate, Forgings, Tube, Shaft Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.37–0.44 |
| Chromium (Cr) | 0.80–1.10 |
| Manganese (Mn) | 0.50–0.80 |
| Silicon (Si) | 0.17–0.37 |
| Phosphorus (P) | ≤0.035 |
| Sulfur (S) | ≤0.035 |
Chromium improves hardenability, wear resistance, fatigue strength, and overall mechanical performance.
Mechanical Properties
Quenched & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | ≥980 MPa |
| Yield Strength | ≥785 MPa |
| Elongation | ≥9% |
| Reduction of Area | ≥45% |
| Impact Energy | ≥47 J |
| Hardness | 28–32 HRC |
| Elastic Modulus | 206 GPa |
Induction Hardened Condition
| Property | Value |
|---|---|
| Surface Hardness | 50–58 HRC |
| Core Toughness | Excellent |
| Wear Resistance | Outstanding |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1510°C |
| Thermal Conductivity | 42 W/m·K |
| Electrical Resistivity | 0.22 μΩ·m |
| Thermal Expansion Coefficient | 11.5 × 10⁻⁶/K |
| Specific Heat Capacity | 460 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 |
40Cr is not corrosion resistant and should be protected in harsh environments.
Recommended surface treatments:
- Black Oxide
- Hard Chrome Plating
- Zinc Plating
- Electroless Nickel Plating
- QPQ Treatment
- Phosphate Coating
- Powder Coating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Good |
| MIG Welding | Good |
| Arc Welding | Good |
| Resistance Welding | Moderate |
| Spot Welding | Moderate |
Recommended welding precautions:
- Preheat: 200–300°C
- Controlled Cooling
- Stress Relief Heat Treatment
For critical components, welding after heat treatment should be carefully controlled.
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Drilling | Good |
| Grinding | Excellent |
| Threading | Good |
| Broaching | Good |
Machinability Comparison
| Material | Machinability |
|---|---|
| 45# Steel | Excellent |
| 40Cr | Excellent |
| 20Cr | Excellent |
| 4140 | Good |
| 4340 | Moderate |
40Cr is one of the most commonly machined alloy steels in CNC manufacturing.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 820–860°C |
| Cooling Method | Furnace Cool |
Normalizing
| Parameter | Value |
|---|---|
| Temperature | 850–880°C |
| Cooling Method | Air Cool |
Quenching
| Parameter | Value |
|---|---|
| Temperature | 840–870°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 520–680°C |
| Purpose | Strength & Toughness Balance |
Induction Hardening
| Property | Value |
|---|---|
| Surface Hardness | 50–58 HRC |
| Hardened Depth | 1–8 mm |
Nitriding
| Property | Value |
|---|---|
| Surface Hardness | 60–70 HRC |
| Wear Resistance | Excellent |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| GB/T (China) | 40Cr |
| SAE/AISI (USA) | 5140 (Approximate) / 4140 (Closest Mechanical Equivalent) |
| ASTM (USA) | AISI 4140 |
| UNS | G41400 |
| EN (Europe) | 41Cr4 / 42CrMo4 (Application Dependent) |
| DIN (Germany) | 1.7035 / 41Cr4 |
| JIS (Japan) | SCr440 |
| ISO | 41Cr4 |
Note: In engineering applications, 40Cr is most commonly compared with AISI 4140, although the chemical composition is closer to AISI 5140.
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Alloy Plate | Yes |
| Forgings | Yes |
| Mechanical Tube | Yes |
| Ground Shafting | Yes |
| Pre-Hardened Bar | Yes |
| Precision Machined Components | Yes |
Typical Applications
Power Transmission Industry
- Drive Shafts
- Splined Shafts
- Couplings
- Transmission Components
Gear Manufacturing
- Spur Gears
- Helical Gears
- Worm Gears
- Pinions
Automotive Industry
- Axles
- Steering Components
- Suspension Parts
- Drive Systems
Construction Machinery
- Excavator Pins
- Loader Components
- Hydraulic Components
- Structural Parts
Mold Industry
- Mold Bases
- Fixture Components
- Tool Holders
General Machinery
- Rollers
- Shafts
- Wear Parts
- Mechanical Assemblies
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Outstanding |
| CNC Milling | Outstanding |
| Heat Treatment | Outstanding |
| Induction Hardening | Outstanding |
| Nitriding | Outstanding |
| Forging | Excellent |
| Precision Grinding | Excellent |
| Hard Chrome Plating | Excellent |
Advantages
Excellent Strength
Suitable for medium-to-heavy-duty applications.
Good Toughness
Performs well under shock loading.
Excellent Wear Resistance
Especially after induction hardening or nitriding.
Outstanding Machinability
Ideal for precision machining.
Good Fatigue Resistance
Suitable for rotating and cyclic-loaded components.
Cost Effective
Lower cost than nickel alloy steels.
Limitations
Limited Corrosion Resistance
Requires surface protection.
Lower Toughness Than 4340
Not suitable for ultra-critical aerospace applications.
Heat Treatment Required
For maximum performance.
Heavier Than Aluminum Alloys
Not suitable for lightweight structures.
Comparison with Other Alloy Steels
| Property | 40Cr | 4140 | 5140 | 4340 | 45# Steel |
|---|---|---|---|---|---|
| Carbon Content | 0.40% | 0.40% | 0.40% | 0.40% | 0.45% |
| Chromium Content | Yes | Yes + Mo | Yes | Yes + Ni + Mo | No |
| Strength | High | Very High | High | Exceptional | Medium |
| Hardenability | Good | Excellent | Good | Outstanding | Moderate |
| Cost | Moderate | Higher | Similar | Highest | Lowest |
Comparison with Engineering Materials
| Material | Yield Strength | Hardness Potential | Fatigue Resistance |
|---|---|---|---|
| 40Cr | ≥785 MPa | 58 HRC | Excellent |
| SAE 4140 | 655–1200 MPa | 58 HRC | Excellent |
| SAE 5140 | 650–900 MPa | 60 HRC | Excellent |
| SAE 4340 | 740–1600 MPa | 60 HRC | Outstanding |
| 45# Steel | ≥355 MPa | 50 HRC | Good |
| 17-4PH Stainless | 860–1170 MPa | 44 HRC | Excellent |
Available Surface Finishes
Raw Finishes
- Hot Rolled Finish
- Annealed Finish
- Quenched & Tempered Finish
- Ground Finish
Functional Finishes
- Induction Hardened Finish
- Nitrided Finish
- Precision Ground Finish
Protective Finishes
- Black Oxide
- Hard Chrome Plating
- Zinc Plating
- Electroless Nickel Plating
- QPQ Treatment
- Phosphate Coating
Frequently Asked Questions (FAQ)
What is 40Cr steel?
40Cr is a medium-carbon chromium alloy steel widely used for shafts, gears, axles, and mechanical components requiring high strength and wear resistance.
What is 40Cr used for?
Typical applications include:
- Shafts
- Gears
- Axles
- Hydraulic Components
- Mold Bases
- Construction Machinery Parts
What is the equivalent material to 40Cr?
Common equivalents include:
- AISI 4140 (Mechanical Equivalent)
- AISI 5140 (Chemical Equivalent)
- DIN 41Cr4
- JIS SCr440
What is the difference between 40Cr and 45# steel?
| Property | 40Cr | 45# Steel |
|---|---|---|
| Chromium Content | Yes | No |
| Hardenability | Better | Lower |
| Strength | Higher | Lower |
| Wear Resistance | Better | Lower |
Can 40Cr be induction hardened?
Yes. Surface hardness can reach 50–58 HRC.
Can 40Cr be nitrided?
Yes. Nitriding can achieve surface hardness of 60–70 HRC with excellent wear resistance.
Is 40Cr suitable for gears?
Yes. It is widely used for medium-load gears, shafts, and transmission components.
Can 40Cr be welded?
Yes, but preheating and stress-relief treatment are recommended.
Why is 40Cr widely used in machinery manufacturing?
Because it combines:
- High Strength
- Good Toughness
- Excellent Machinability
- Good Wear Resistance
- Cost Efficiency
making it one of the most versatile engineering steels available.
Does GCNOV provide custom manufacturing services for 40Cr?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Shaft Manufacturing
- Gear Machining
- Induction Hardening
- Nitriding
- Precision Grinding
- Hard Chrome Plating
- Prototype Development
- Low-Volume Production
- Mass Production