en 
fra 
de 
ru 
ara 
gle 
it 
jp 
kor 
th 
zh Crankshaft Materials Explained: Cast Iron, Ductile Iron, and Alloy Options
2026-01-13 09:14:28 hits：0
Introduction: Why Crankshaft Material Matters
The crankshaft is the heart of any internal combustion engine, converting piston motion into rotational power. Choosing the right material impacts:
Strength and fatigue resistance
Weight and balance
Cost and machinability
Longevity and maintenance
Whether you're an engineer, mechanic, or engine enthusiast, understanding crankshaft materials helps you make smarter sourcing or design decisions.
Common Crankshaft Materials: Overview
Primary crankshaft materials include:
Cast Iron (Grey Cast Iron)
Ductile Iron (Nodular Iron)
Cast Steel
Forged Alloy Steel (e.g., SAE 4340, 4330)
Billet Steel
Each has unique properties, costs, and best applications.
Cast Iron Crankshafts
What is Cast Iron?
Cast iron is an iron-carbon alloy (2–4% carbon) with excellent castability and vibration damping.
Characteristics:
Tensile strength: 482–551 MPa
Durable for low to medium stress engines
Cost-effective for economy passenger cars
Pros & Cons:
Pros | Cons |
Low production cost | Brittle; low fatigue strength |
Good vibration damping | Not ideal for high-performance engines |
Easy to cast and machine | Prone to cracking under high stress |
Applications: Low to moderate performance engines.
Ductile Iron (Nodular Iron) Crankshafts
What is Ductile Iron?
Ductile iron is cast iron alloyed with magnesium or cerium, forming graphite nodules that improve strength and ductility.
Characteristics:
Tensile strength: up to 655 MPa
Better fatigue resistance than grey cast iron
Cost: Slightly higher but still affordable
Pros: Increased toughness, machinability, fatigue resistance
Cons: Still weaker than forged steel, difficult to weld or repair
Applications: Mid-range passenger vehicles and moderately tuned engines.
Cast Steel Crankshafts
Overview:
Made by pouring molten steel into molds
Tensile strength: ~724 MPa
Suitable for engines up to 368 kW (~500 hp)
Pros & Cons:
Pros | Cons |
Higher strength than cast iron | Lower ductility than forged steel |
Cost-effective for moderate power | Potential casting defects |
Good wear resistance | Less uniform grain structure |
Forged Alloy Steel Crankshafts
What is Forged Steel?
Forging compresses heated steel billets, aligning grain structures for maximum strength and fatigue resistance.
Common Grades: SAE 4340, 4330
Tensile Strength: 965–1000 MPa
Applications: High-performance street engines, racing, aerospace
Advantages: Superior strength, durability, can be heat-treated
Cost: Higher than cast options but justified for performance gains
Billet Steel Crankshafts
Machined from solid forged steel billets
Maximum precision and strength
Materials: SAE 4330, 300M
Tensile strength: >1000 MPa
Applications: Extreme racing, aerospace
Pros & Cons:
Pros | Cons |
Maximum strength and precision | Highest cost |
Customizable for specific builds | Longer production time |
Ideal for extreme performance | Requires specialized equipment |
Comparing Crankshaft Materials
Material | Tensile Strength (MPa) | Fatigue Resistance | Cost | Common Applications |
Cast Iron | 482–551 | Low | Low | Economy cars |
Ductile Iron | Up to 655 | Medium | Moderate | Mid-range cars, light trucks |
Cast Steel | ~724 | Medium-High | Moderate | Moderate performance engines |
Forged Steel 4340 | 965–1000 | High | High | Racing, high-performance |
Billet Steel 4330/300M | 1000+ | Very High | Very High | Extreme racing, aerospace |
Factors Influencing Material Selection
Engine Power & Torque: High-power engines need forged or billet steel.
RPM & Load: High-speed engines need materials that flex without cracking.
Cost Constraints: Cast or ductile iron is budget-friendly.
Operating Conditions: Alloy steels resist heat, stress, and corrosion.
Maintenance: Repairability varies; cast materials easier to repair than forged steel.
Internal Links:
Learn how material choice affects crankshaft casting and manufacturing
Compare blank vs finished crankshaft options
See our custom material selection options
Future Trends
Composite materials: Lighter, lower inertia crankshafts
3D printing: Custom alloys and geometries
Advanced coatings: Reduce wear and thermal stress
Sustainable materials: Recycled steels, bio-composites
Conclusion
Choosing the right crankshaft material requires balancing strength, durability, cost, and application.
Cast iron: Economy, low stress
Ductile iron: Tougher, mid-range applications
Cast steel: Moderate performance
Forged steel: High-performance and racing
Billet steel: Maximum strength, precision, extreme applications
For custom engine builds, selecting the appropriate material is key to reliability and performance.
Take Action:
Contact us to select the ideal crankshaft material for your engine
Request a quote for custom crankshaft blanks or finished products
Take Action: Request a Quote
Ready to source crankshafts for your engine project?
Get a quote for custom crankshaft blanks suited to your machining setup (learn more)
Explore machined crankshafts ready for immediate installation (learn more)
Our team can recommend the best option for your engine build and provide delivery schedules tailored to your project needs.
