Overview
42CrMo Steel is a high-strength chromium-molybdenum alloy steel widely used in heavy-duty engineering applications requiring excellent strength, toughness, hardenability, fatigue resistance, wear resistance, and impact performance.
As the Chinese equivalent of AISI 4140 and EN 42CrMo4, 42CrMo is one of the most important engineering steels used in manufacturing shafts, gears, hydraulic components, molds, oilfield equipment, and construction machinery.
Compared with 40Cr, 42CrMo offers:
- Higher strength
- Better hardenability
- Improved fatigue resistance
- Superior high-temperature performance
- Better toughness after heat treatment
42CrMo is widely used in:
- Heavy-Duty Shafts
- Hydraulic Cylinders
- Gears & Pinions
- Oil & Gas Equipment
- Wind Power Components
- Construction Machinery
- Mining Equipment
- Mold Bases
Because of its exceptional balance between strength and toughness, 42CrMo is considered one of the most versatile alloy steels in modern engineering.
Material Specification
| Property | Value |
|---|---|
| Material Designation | 42CrMo |
| Standard | GB/T 3077 |
| Material Family | Chromium-Molybdenum Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Annealed, Quenched & Tempered |
| Standard Forms | Bar, Plate, Forgings, Tube, Shaft Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.38–0.45 |
| Chromium (Cr) | 0.90–1.20 |
| Molybdenum (Mo) | 0.15–0.30 |
| Manganese (Mn) | 0.50–0.80 |
| Silicon (Si) | 0.17–0.37 |
| Phosphorus (P) | ≤0.035 |
| Sulfur (S) | ≤0.035 |
The addition of molybdenum significantly improves hardenability, temper resistance, and fatigue strength.
Mechanical Properties
Quenched & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | ≥1080 MPa |
| Yield Strength | ≥930 MPa |
| Elongation | ≥12% |
| Reduction of Area | ≥45% |
| Impact Energy | ≥63 J |
| Hardness | 28–35 HRC |
| Elastic Modulus | 206 GPa |
High Strength Condition
| Property | Value |
|---|---|
| Tensile Strength | 1100–1400 MPa |
| Yield Strength | 950–1200 MPa |
| Hardness | Up to 55 HRC |
Nitrided Condition
| Property | Value |
|---|---|
| Surface Hardness | 60–72 HRC |
| Wear Resistance | Outstanding |
| Fatigue Resistance | Outstanding |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1540°C |
| Thermal Conductivity | 42 W/m·K |
| Electrical Resistivity | 0.22 μΩ·m |
| Thermal Expansion Coefficient | 11.1 × 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 |
42CrMo is not a corrosion-resistant alloy and requires surface protection in aggressive environments.
Recommended surface treatments:
- Gas Nitriding
- QPQ Treatment
- Black Oxide
- Hard Chrome Plating
- Electroless Nickel Plating
- Zinc Plating
- Phosphate Coating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Good |
| MIG Welding | Good |
| Arc Welding | Good |
| Resistance Welding | Moderate |
| Spot Welding | Moderate |
Recommended welding procedures:
- Preheat: 200–350°C
- Controlled Cooling
- Post-Weld Stress Relief
For critical structural applications, welding should be followed by heat treatment.
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 |
| 42CrMo | Good–Excellent |
| 4140 | Good |
| 4340 | Moderate |
42CrMo is commonly supplied pre-hardened for machining applications.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 830–880°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 | 540–680°C |
| Purpose | Strength & Toughness Optimization |
Nitriding
| Property | Value |
|---|---|
| Surface Hardness | 60–72 HRC |
| Case Depth | 0.2–0.7 mm |
Induction Hardening
| Property | Value |
|---|---|
| Surface Hardness | 52–60 HRC |
| Hardened Depth | 1–8 mm |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| GB/T (China) | 42CrMo |
| SAE/AISI (USA) | 4140 |
| ASTM (USA) | AISI 4140 |
| UNS | G41400 |
| EN (Europe) | 42CrMo4 |
| DIN (Germany) | 1.7225 |
| JIS (Japan) | SCM440 |
| ISO | 42CrMo4 |
42CrMo is globally recognized as the Chinese equivalent of AISI 4140 and DIN 42CrMo4.
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
Power Transmission Industry
- Drive Shafts
- Splined Shafts
- Couplings
- Gear Shafts
Gear Manufacturing
- Spur Gears
- Helical Gears
- Pinions
- Worm Gears
Hydraulic Industry
- Hydraulic Rods
- Cylinder Components
- Valve Bodies
- Pump Shafts
Oil & Gas Industry
- Drill Collars
- Wellhead Equipment
- Pressure Components
- Structural Parts
Construction & Mining Machinery
- Excavator Pins
- Loader Components
- Crusher Parts
- Wear Components
Mold Manufacturing
- Plastic Mold Bases
- Forging Dies
- Tool Holders
- Fixture Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Outstanding |
| CNC Milling | Outstanding |
| Heat Treatment | Outstanding |
| Nitriding | Outstanding |
| Induction Hardening | Outstanding |
| Forging | Excellent |
| Precision Grinding | Excellent |
| Hard Chrome Plating | Excellent |
Advantages
High Strength
Suitable for heavy-duty load-bearing applications.
Excellent Toughness
Performs well under impact and shock loads.
Outstanding Fatigue Resistance
Ideal for rotating and cyclic-loaded components.
Excellent Hardenability
Uniform hardness throughout large sections.
Excellent Wear Resistance
Particularly after nitriding or induction hardening.
Widely Available
Commonly stocked worldwide.
Limitations
Limited Corrosion Resistance
Requires protective surface treatments.
Higher Cost Than 40Cr
Due to molybdenum alloying.
Welding Requires Control
Preheating and stress-relief recommended.
Heavier Than Aluminum Alloys
Not suitable for lightweight structures.
Comparison with Other Alloy Steels
| Property | 42CrMo | 4140 | 40Cr | 4340 | SCM440 |
|---|---|---|---|---|---|
| Carbon Content | 0.42% | 0.40% | 0.40% | 0.40% | 0.40% |
| Chromium | Yes | Yes | Yes | Yes | Yes |
| Molybdenum | Yes | Yes | No | Yes | |
| Strength | Very High | Very High | High | Exceptional | Very High |
| Hardenability | Excellent | Excellent | Good | Outstanding | Excellent |
| Cost | Moderate | Moderate | Lower | Higher | Moderate |
Comparison with Engineering Materials
| Material | Yield Strength | Hardness Potential | Fatigue Resistance |
|---|---|---|---|
| 42CrMo | ≥930 MPa | 60 HRC | Excellent |
| SAE 4140 | 655–1200 MPa | 58 HRC | Excellent |
| 40Cr | ≥785 MPa | 58 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
- Nitrided Finish
- Induction Hardened Finish
- Precision Ground Finish
Protective Finishes
- Black Oxide
- Hard Chrome Plating
- Electroless Nickel Plating
- Zinc Plating
- QPQ Treatment
- Phosphate Coating
Frequently Asked Questions (FAQ)
What is 42CrMo steel?
42CrMo is a chromium-molybdenum alloy steel known for high strength, toughness, fatigue resistance, and excellent hardenability.
What is 42CrMo used for?
Typical applications include:
- Shafts
- Gears
- Hydraulic Cylinders
- Oilfield Equipment
- Mold Bases
- Heavy Machinery Components
What is the equivalent material to 42CrMo?
Common equivalents include:
- AISI 4140
- DIN 42CrMo4
- JIS SCM440
- EN 42CrMo4
What is the difference between 42CrMo and 40Cr?
| Property | 42CrMo | 40Cr |
|---|---|---|
| Molybdenum Content | Yes | No |
| Strength | Higher | Lower |
| Hardenability | Better | Lower |
| Fatigue Resistance | Better | Good |
Can 42CrMo be nitrided?
Yes. Surface hardness can reach 60–72 HRC after nitriding.
Can 42CrMo be induction hardened?
Yes. Surface hardness can reach 52–60 HRC.
Is 42CrMo suitable for shafts?
Yes. It is one of the most widely used shaft materials in heavy machinery and hydraulic systems.
Can 42CrMo be welded?
Yes, but preheating and post-weld stress relief are recommended.
Why is 42CrMo widely used in engineering?
Because it combines:
- High Strength
- Excellent Toughness
- Outstanding Fatigue Resistance
- Excellent Hardenability
- Good Machinability
making it one of the most versatile engineering steels available.
Does GCNOV provide custom manufacturing services for 42CrMo?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Shaft Manufacturing
- Gear Machining
- Nitriding
- Induction Hardening
- Heat Treatment
- Precision Grinding
- Hard Chrome Plating
- Prototype Development
- Low-Volume Production
- Mass Production