Overview
SAE/AISI 4130 Steel, commonly known as Chromoly Steel (Chrome-Moly Steel), is a low-alloy steel containing chromium and molybdenum as strengthening elements. It is widely recognized for its excellent combination of strength, toughness, weldability, fatigue resistance, and heat treatment capability.
Compared with carbon steels such as 1045 and 1050, SAE 4130 offers significantly higher strength-to-weight ratio, better hardenability, and superior fatigue performance.
SAE 4130 is widely used in:
- Aerospace Components
- Motorsport Chassis
- Bicycle Frames
- Roll Cages
- Aircraft Structures
- Oil & Gas Equipment
- Pressure Vessels
- Industrial Machinery
Because of its excellent mechanical properties and relatively low weight, 4130 is one of the most popular engineering alloy steels worldwide.
Material Specification
| Property | Value |
|---|---|
| Material Designation | SAE/AISI 4130 |
| Standard | ASTM A29 / SAE J404 |
| UNS Number | G41300 |
| Material Family | Chromium-Molybdenum Alloy Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Standard Forms | Bar, Plate, Tube, Pipe, Forgings, Sheet |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.28–0.33 |
| Chromium (Cr) | 0.80–1.10 |
| Molybdenum (Mo) | 0.15–0.25 |
| Manganese (Mn) | 0.40–0.60 |
| Silicon (Si) | 0.15–0.35 |
| Phosphorus (P) | ≤0.035 |
| Sulfur (S) | ≤0.040 |
The addition of chromium and molybdenum significantly improves strength, hardenability, wear resistance, and fatigue performance.
Mechanical Properties
Normalized Condition
| Property | Value |
|---|---|
| Tensile Strength | 560–760 MPa |
| Yield Strength | 435–560 MPa |
| Elongation | 18–25% |
| Hardness | 170–220 HB |
| Elastic Modulus | 205 GPa |
Quenched & Tempered Condition
| Property | Value |
|---|---|
| Tensile Strength | 850–1100 MPa |
| Yield Strength | 650–900 MPa |
| Elongation | 12–18% |
| Hardness | 28–38 HRC |
Aerospace Grade Condition
| Property | Value |
|---|---|
| Tensile Strength | Up to 1200 MPa |
| Yield Strength | Up to 950 MPa |
| Fatigue Resistance | Excellent |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1425–1540°C |
| Thermal Conductivity | 42 W/m·K |
| Electrical Resistivity | 0.22 μΩ·m |
| Thermal Expansion Coefficient | 11.1 × 10⁻⁶/K |
| Specific Heat Capacity | 475 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Good |
| Dry Atmosphere | Good |
| Outdoor Environment | Moderate |
| Marine Environment | Poor |
| Chemical Environment | Poor |
| Humid Environment | Moderate |
4130 provides slightly better corrosion resistance than plain carbon steels but still requires surface protection for harsh environments.
Recommended surface treatments:
- Zinc Plating
- Electroless Nickel Plating
- Hard Chrome Plating
- Black Oxide
- Phosphate Coating
- Powder Coating
- Painting
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Excellent |
| MIG Welding | Excellent |
| Arc Welding | Good |
| Resistance Welding | Good |
| Spot Welding | Good |
4130 is one of the most weldable alloy steels.
For thicker sections (>6 mm), preheating is often recommended.
Widely used in:
- Aircraft Structures
- Roll Cages
- Racing Chassis
- Tubular Frames
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Drilling | Good |
| Grinding | Excellent |
| Threading | Good |
| Broaching | Good |
Machinability Comparison
| Material | Machinability |
|---|---|
| 1018 | Excellent |
| 1045 | Good–Excellent |
| 4130 | Good |
| 4140 | Good |
| 4340 | Moderate |
| 17-4PH | Good |
4130 offers excellent dimensional stability during machining.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 815–870°C |
| Cooling Method | Furnace Cool |
Normalizing
| Parameter | Value |
|---|---|
| Temperature | 870–925°C |
| Cooling Method | Air Cool |
Quenching
| Parameter | Value |
|---|---|
| Temperature | 845–870°C |
| Cooling Medium | Oil |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 400–700°C |
| Purpose | Toughness & Strength Adjustment |
Hardness After Heat Treatment
| Condition | Hardness |
|---|---|
| Annealed | 150–200 HB |
| Normalized | 170–220 HB |
| Quenched & Tempered | 28–38 HRC |
| Specialized Heat Treatment | Up to 45 HRC |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| SAE/AISI (USA) | 4130 |
| ASTM (USA) | ASTM A29 Grade 4130 |
| UNS | G41300 |
| GB/T (China) | 30CrMo |
| EN (Europe) | 25CrMo4 |
| DIN (Germany) | 1.7218 / 25CrMo4 |
| JIS (Japan) | SCM430 |
| ISO | 25CrMo4 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Alloy Steel Plate | Yes |
| Sheet Metal | Yes |
| Seamless Tube | Yes |
| DOM Tube | Yes |
| Aircraft Tube | Yes |
| Forgings | Yes |
Typical Applications
Aerospace Industry
- Aircraft Fuselage Components
- Landing Gear Parts
- Structural Frames
- Engine Mounts
Motorsport Industry
- Roll Cages
- Racing Chassis
- Suspension Components
- Safety Structures
Bicycle Industry
- High-End Bicycle Frames
- Performance Bike Components
Oil & Gas Industry
- Drill Components
- Pressure Equipment
- Structural Parts
Industrial Machinery
- Shafts
- Couplings
- Structural Components
- Mechanical Assemblies
Defense Industry
- Vehicle Components
- Structural Assemblies
- Mechanical Systems
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Welding | Outstanding |
| Tube Bending | Excellent |
| Heat Treatment | Outstanding |
| TIG Welding | Outstanding |
| Precision Grinding | Excellent |
| Hard Chrome Plating | Excellent |
Advantages
Excellent Strength-to-Weight Ratio
Ideal for lightweight structural applications.
Outstanding Fatigue Resistance
Excellent for cyclic loading conditions.
Excellent Weldability
One of the easiest alloy steels to weld.
Heat Treatable
Achieves significantly higher strength after heat treatment.
Good Toughness
Maintains mechanical performance under impact loading.
Aerospace Approved Material
Widely used in aerospace and motorsports industries.
Limitations
Lower Corrosion Resistance Than Stainless Steel
Requires protective coatings.
More Expensive Than Carbon Steel
Higher material cost than 1045 or 1020.
Lower Wear Resistance Than Tool Steels
Not ideal for severe abrasion applications.
Requires Controlled Heat Treatment
For maximum mechanical performance.
Comparison with Other Alloy Steels
| Property | 4130 | 4140 | 4340 | 1045 | 30CrMo |
|---|---|---|---|---|---|
| Carbon Content | 0.30% | 0.40% | 0.40% | 0.45% | 0.30% |
| Strength | High | Very High | Exceptional | Medium | |
| Weldability | Excellent | Good | Moderate | Good | |
| Toughness | Excellent | Excellent | Outstanding | Good | |
| Weight Efficiency | Excellent | Good | Good | Moderate |
Comparison with Engineering Materials
| Material | Yield Strength | Hardness Potential | Fatigue Resistance |
|---|---|---|---|
| SAE 4130 | 650–900 MPa | 45 HRC | Excellent |
| SAE 4140 | 655–1100 MPa | 58 HRC | Excellent |
| SAE 4340 | 740–1400 MPa | 60 HRC | Outstanding |
| 1045 Steel | 550–700 MPa | 58 HRC | Good |
| SS304 | 205 MPa | Low | Good |
| 17-4PH Stainless | 860–1170 MPa | 44 HRC | Excellent |
Available Surface Finishes
Raw Finishes
- Hot Rolled Finish
- Annealed Finish
- Normalized Finish
- Ground Finish
Protective Finishes
- Zinc Plating
- Electroless Nickel Plating
- Hard Chrome Plating
- Black Oxide
- Phosphate Coating
Decorative Finishes
- Powder Coating
- Spray Painting
- Electrophoretic Coating (E-Coating)
Frequently Asked Questions (FAQ)
What is SAE 4130 steel?
SAE 4130 is a chromium-molybdenum alloy steel known for its high strength, excellent weldability, and superior fatigue resistance.
What is SAE 4130 used for?
Typical applications include:
- Aircraft Structures
- Roll Cages
- Racing Chassis
- Bicycle Frames
- Pressure Vessels
- Industrial Machinery
What is the difference between SAE 4130 and SAE 4140?
| Property | SAE 4130 | SAE 4140 |
|---|---|---|
| Carbon Content | Lower | Higher |
| Weldability | Better | Lower |
| Strength | High | Higher |
| Toughness | Excellent | Excellent |
Is SAE 4130 suitable for aerospace applications?
Yes. 4130 is one of the most widely used aerospace structural steels.
Can SAE 4130 be welded?
Yes. It offers excellent TIG and MIG welding performance.
What hardness can SAE 4130 achieve?
- Quenched & Tempered: 28–38 HRC
- Specialized Heat Treatment: Up to 45 HRC
Is SAE 4130 stronger than 1045?
Yes. Heat-treated 4130 provides significantly higher strength and fatigue resistance than 1045.
Why is SAE 4130 called Chromoly?
Because it contains:
- Chromium (Cr)
- Molybdenum (Mo)
which improve strength and hardenability.
Is SAE 4130 suitable for CNC machining?
Yes. It offers good machinability and dimensional stability.
Does GCNOV provide custom manufacturing services for SAE 4130?
Yes. GCNOV provides:
- CNC Turning
- CNC Milling
- Aerospace Tube Fabrication
- Precision Welding
- Roll Cage Manufacturing
- Heat Treatment
- Precision Grinding
- Surface Finishing
- Prototype Development
- Low-Volume Production
- Mass Production