Overview
20Cr Steel is a low-carbon chromium alloy steel widely used for carburizing and case-hardening applications. It combines a hard, wear-resistant surface with a tough, ductile core, making it ideal for gears, shafts, pins, bushings, and transmission components.
As one of the most commonly used alloy steels in China, 20Cr offers excellent machinability, good cold formability, and outstanding carburizing performance. After carburizing and quenching, it can achieve high surface hardness while maintaining core toughness.
20Cr is widely used in:
- Automotive Transmission Gears
- Gear Shafts
- Spline Shafts
- Pinions
- Bushings
- Camshafts
- Machinery Components
- Agricultural Equipment
Compared with 20# carbon steel, 20Cr provides significantly better hardenability and wear resistance. Compared with 20CrMnTi, it offers lower hardenability but lower material cost.
20Cr Alloy Steel
A low-carbon chromium alloy structural steel offering good hardenability, core toughness, machinability, and excellent surface hardness after carburizing.
A versatile carburizing steel.
20Cr is a low-carbon chromium alloy steel developed for parts requiring a hard, wear-resistant surface and a tough internal core.
Its carbon content is maintained at approximately 0.20%, while chromium improves hardenability, wear resistance, and tempering stability.
After carburizing and quenching, 20Cr can achieve a surface hardness of approximately 58–62 HRC while retaining the toughness required for gears, shafts, pins, cams, and transmission components.
Key technical specifications.
Chemical Composition
Weight percentage| Element | Symbol | Content |
|---|---|---|
| Carbon | C | 0.18–0.24% |
| Silicon | Si | 0.17–0.37% |
| Manganese | Mn | 0.50–0.80% |
| Chromium | Cr | 0.70–1.10% |
| Phosphorus | P | ≤0.035% |
| Sulfur | S | ≤0.035% |
| Nickel | Ni | ≤0.30% |
| Copper | Cu | ≤0.25% |
Optimized before carburizing.
20Cr is generally machined in its normalized or quenched-and-tempered condition before carburizing. Final grinding is performed after heat treatment where tight dimensional or surface requirements apply.
Need shafts, gears, pins, or precision turned parts?
From machinable core to hardened surface.
Refines the structure and prepares the material for machining and subsequent treatment.
Increases the carbon concentration at the component surface.
Develops the hardened surface layer and required core properties.
Relieves residual stress while retaining high surface hardness.
Made for motion and controlled wear.
Transmission Gears
Automotive and industrial gears operating under moderate loads and repeated surface contact.
Gear Shafts
Machined shafts requiring a wear-resistant surface and a tough supporting core.
Cams & Worms
Moving components exposed to friction, sliding contact, and repeated mechanical cycles.
Piston Pins
Precision cylindrical parts requiring strength, wear resistance, and dimensional consistency.
Spline Shafts
Torque-transfer components for industrial drives and mechanical transmission assemblies.
Clutch Components
Clutch claws and engagement parts requiring hardened contact surfaces.
Dimensional verification, surface inspection, hardness testing, and production traceability.
Common 20Cr questions.
20Cr is a Chinese low-carbon chromium alloy structural steel commonly used for carburized gears, shafts, pins, cams, worms, and transmission parts.
After carburizing, quenching, and low-temperature tempering, 20Cr can typically reach approximately 58–62 HRC at the surface.
SAE/AISI 5120 and JIS SCr420 are commonly referenced as approximate equivalents. Final substitution should be verified against chemical, mechanical, and heat-treatment requirements.
Yes. GCNOV supports CNC turning, milling, drilling, gear manufacturing, grinding, carburizing, prototyping, low-volume production, and mass production.
Turn your alloy-steel design into production parts.
Send your CAD files, drawings, material requirements, tolerances, heat-treatment specifications, and quantities for an engineering quotation.
Material Specification
| Property | Value |
|---|---|
| Material Designation | 20Cr |
| Standard | GB/T 3077 |
| Material Family | Chromium Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Annealed, Normalized, Hot Rolled |
| Standard Forms | Bar, Forgings, Plate, Tube, Shaft Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.17–0.24 |
| Chromium (Cr) | 0.70–1.00 |
| 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, and fatigue strength.
Mechanical Properties
Normalized Condition
| Property | Value |
|---|---|
| Tensile Strength | ≥540 MPa |
| Yield Strength | ≥390 MPa |
| Elongation | ≥25% |
| Reduction of Area | ≥55% |
| Hardness | ≤179 HB |
| Elastic Modulus | 206 GPa |
Carburized and Quenched Condition
| Property | Value |
|---|---|
| Surface Hardness | 58–62 HRC |
| Core Hardness | 30–40 HRC |
| Wear Resistance | Excellent |
| Impact Toughness | Good |
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Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1420–1510°C |
| Thermal Conductivity | 43 W/m·K |
| Electrical Resistivity | 0.22 μΩ·m |
| Thermal Expansion Coefficient | 11.7 × 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 |
20Cr is not a stainless steel and requires protective treatment for corrosion-prone environments.
Recommended surface treatments:
- Carburizing
- Black Oxide
- Zinc Plating
- Phosphate Coating
- Electroless Nickel Plating
- QPQ Treatment
- Hard Chrome Plating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Good |
| MIG Welding | Good |
| Arc Welding | Good |
| Resistance Welding | Good |
| Spot Welding | Good |
Due to its low carbon content, 20Cr has good weldability.
Recommended:
- Preheating for thick sections
- Stress relief for critical parts
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Excellent |
| CNC Milling | Excellent |
| Drilling | Excellent |
| Grinding | Excellent |
| Gear Hobbing | Excellent |
| Broaching | Excellent |
Machinability Comparison
| Material | Machinability |
|---|---|
| 20# Steel | Excellent |
| 20Cr | Excellent |
| 40Cr | Good |
| 20CrMnTi | Good |
| 8620 | Excellent |
20Cr is commonly machined before carburizing and final grinding.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 820–860°C |
| Cooling Method | Furnace Cool |
Normalizing
| Parameter | Value |
|---|---|
| Temperature | 870–920°C |
| Cooling Method | Air Cool |
Carburizing
| Parameter | Value |
|---|---|
| Temperature | 900–950°C |
| Case Depth | 0.5–2.0 mm |
| Surface Hardness | 58–62 HRC |
Quenching
| Parameter | Value |
|---|---|
| Temperature | 820–850°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 150–200°C |
| Purpose | Stress Relief |
Carbonitriding
| Property | Value |
|---|---|
| Surface Hardness | 58–63 HRC |
| Wear Resistance | Excellent |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| GB/T (China) | 20Cr |
| SAE/AISI (USA) | 5120 (Approximate Equivalent) |
| ASTM (USA) | AISI 5120 |
| UNS | G51200 |
| EN (Europe) | 16Cr4 |
| DIN (Germany) | 1.7033 |
| JIS (Japan) | SCr420 |
| ISO | 16Cr4 |
Note: 20Cr is often considered the Chinese equivalent of AISI 5120 and JIS SCr420 for carburizing applications.
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Forgings | Yes |
| Gear Blanks | Yes |
| Mechanical Tube | Yes |
| Precision Shaft Stock | Yes |
| Alloy Plate | Limited |
Typical Applications
Automotive Industry
- Transmission Gears
- Gear Shafts
- Differential Components
- Spline Shafts
Gear Manufacturing
- Spur Gears
- Helical Gears
- Pinions
- Worm Gears
Industrial Machinery
- Couplings
- Shafts
- Bushings
- Drive Components
Agricultural Equipment
- Gear Systems
- PTO Components
- Transmission Parts
Construction Machinery
- Pins
- Bushings
- Drive Assemblies
- Hydraulic Components
General Engineering
- Wear Parts
- Mechanical Components
- Rotating Equipment
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Outstanding |
| CNC Milling | Outstanding |
| Gear Hobbing | Outstanding |
| Carburizing | Outstanding |
| Carbonitriding | Outstanding |
| Precision Grinding | Excellent |
| Forging | Excellent |
| QPQ Treatment | Excellent |
Advantages
Excellent Carburizing Performance
Ideal for case-hardened components.
Tough Core Structure
Provides good impact resistance.
Excellent Machinability
Easy to machine before heat treatment.
Good Wear Resistance
After carburizing and quenching.
Cost Effective
Lower cost than nickel alloy carburizing steels.
Widely Available
Commonly stocked throughout Asia and global markets.
Limitations
Limited Corrosion Resistance
Requires protective coatings.
Lower Fatigue Strength Than 20CrMnTi or 9310
Not suitable for extreme aerospace applications.
Heat Treatment Required
Full performance depends on carburizing.
Lower Core Strength Than 40Cr
Not ideal for through-hardened applications.
Comparison with Other Alloy Steels
| Property | 20Cr | 5120 | 20CrMnTi | 8620 | 40Cr |
|---|---|---|---|---|---|
| Carbon Content | 0.20% | 0.20% | 0.20% | 0.20% | 0.40% |
| Chromium Content | Yes | Yes | Yes | Yes | Yes |
| Nickel Content | No | No | No | Yes | No |
| Carburizing Ability | Excellent | Excellent | Outstanding | Outstanding | Moderate |
| Core Toughness | Good | Good | Better | Excellent | High |
Comparison with Engineering Materials
| Material | Yield Strength | Surface Hardness | Wear Resistance |
|---|---|---|---|
| 20Cr | ≥390 MPa | 58–62 HRC | Excellent |
| 20CrMnTi | ≥450 MPa | 58–62 HRC | Outstanding |
| SAE 8620 | 550–850 MPa | 58–64 HRC | Outstanding |
| SAE 9310 | 760–1100 MPa | 58–65 HRC | Exceptional |
| 40Cr | 540–900 MPa | 55–60 HRC | Excellent |
| 17-4PH Stainless | 860–1170 MPa | 44 HRC | Good |
Available Surface Finishes
Raw Finishes
- Hot Rolled Finish
- Annealed Finish
- Normalized Finish
- Precision Machined Finish
Functional Finishes
- Carburized Finish
- Carbonitrided Finish
- Ground Finish
- Precision Gear Finish
Protective Finishes
- Black Oxide
- Zinc Plating
- Nickel Plating
- Phosphate Coating
- Hard Chrome Plating
- QPQ Treatment
Frequently Asked Questions (FAQ)
What is 20Cr steel?
20Cr is a low-carbon chromium alloy steel primarily used for carburized gears, shafts, and wear-resistant mechanical components.
What is 20Cr used for?
Typical applications include:
- Gears
- Pinions
- Gear Shafts
- Bushings
- Automotive Transmission Parts
- Industrial Machinery Components
What is the difference between 20Cr and 40Cr?
| Property | 20Cr | 40Cr |
|---|---|---|
| Carbon Content | Lower | Higher |
| Carburizing Performance | Better | Moderate |
| Core Strength | Lower | Higher |
| Typical Use | Gears | Shafts & Structural Parts |
What is the equivalent material to 20Cr?
Common equivalents include:
- AISI 5120
- DIN 16Cr4
- JIS SCr420
Is 20Cr suitable for gears?
Yes. 20Cr is widely used for carburized gears and transmission components.
Can 20Cr be carburized?
Yes. It is specifically designed for carburizing and case-hardening applications.
What hardness can 20Cr achieve?
After carburizing and quenching:
- Surface Hardness: 58–62 HRC
- Core Hardness: 30–40 HRC
Is 20Cr better than 20# steel?
Yes. The chromium content significantly improves hardenability and wear resistance.
Can 20Cr be welded?
Yes. Its low carbon content provides relatively good weldability.
Does GCNOV provide custom manufacturing services for 20Cr?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Gear Manufacturing
- Gear Hobbing
- Carburizing
- Carbonitriding
- Precision Grinding
- QPQ Treatment
- Prototype Development
- Low-Volume Production
- Mass Production