Ductile Iron Grades Explained: Complete Guide to GGG40, GGG50, GGG60, GGG70 for International Buyers

Quick Answer

Ductile iron grades (GGG40, GGG50, GGG60, GGG70) indicate minimum tensile strength in MPa. GGG40 offers highest ductility (10-18% elongation) for impact applications; GGG50 balances strength and ductility (7-12% elongation) for general use; GGG60 provides higher strength (3-7% elongation) for pressure applications; GGG70 delivers maximum strength (2-5% elongation) for wear-resistant components. Selection depends on required tensile strength, ductility, and hardness for specific applications.

Overview: Why Grade Understanding Matters

Ductile iron grade selection directly affects component performance, service life, and cost. Choosing the wrong grade can result in premature failure, excessive wear, or unnecessary expense. Understanding grade differences enables informed material specification and supplier communication.

Grade selection impact:

Key principle: Higher grade numbers indicate higher strength but lower ductility — selection requires balancing these properties for specific applications.

Ductile Iron Grade Designations

Understanding Grade Naming

Common designation systems:

Grade number meaning:

• GGG40 = Minimum tensile strength 400 MPa (40 kgf/mm² in old DIN system)

• GGG50 = Minimum tensile strength 500 MPa

• GGG60 = Minimum tensile strength 600 MPa

• GGG70 = Minimum tensile strength 700 MPa




Complete Grade Comparison




Standard ductile iron grades:




Grade (DIN)	Grade (EN)	Grade (ASTM)	Tensile Strength	Yield Strength	Elongation	Hardness (HB)
GGG40	EN-GJS-400-15	60-40-15	400 MPa	250 MPa	15%	140-190
GGG50	EN-GJS-500-7	70-50-05	500 MPa	320 MPa	7%	170-230
GGG50	EN-GJS-500-7	70-50-05	500 MPa	350 MPa	7%	180-240
GGG60	EN-GJS-600-3	80-60-03	600 MPa	370 MPa	3%	200-260
GGG70	EN-GJS-700-2	100-70-03	700 MPa	420 MPa	2%	230-290
GGG80	EN-GJS-800-2	120-90-02	800 MPa	480 MPa	2%	250-320

Note: GGG40/50/60/70 are most common for general industrial applications.




Mechanical Properties by Grade




Tensile Strength




What tensile strength means:




Tensile strength indicates the maximum stress material can withstand while being stretched or pulled before breaking. Higher tensile strength enables thinner sections and higher load capacity.




Tensile strength by grade:




Grade	Minimum Tensile Strength	Typical Applications
GGG50	500 MPa (72,500 psi)	General engineering, pump housings, valve bodies
GGG60	600 MPa (87,000 psi)	Pressure-containing parts, gears, crankshafts
GGG70	700 MPa (101,500 psi)	High-stress components, wear-resistant parts

Elongation (Ductility)




What elongation means:




Elongation measures how much material can stretch before breaking, expressed as percentage of original length. Higher elongation indicates better ductility and impact resistance.




Elongation by grade:




Grade	Minimum Elongation	Ductility Level	Best For
GGG50	7-12%	Moderate ductility	General applications, balanced properties
GGG60	3-7%	Limited ductility	Higher strength, moderate impact
GGG70	2-5%	Low ductility	Maximum strength, minimal impact

Strength-Ductility Trade-off:




Higher Strength ←→ Higher Ductility
(GGG70, GGG80)    (GGG40)

You cannot maximize both simultaneously.
Selection requires prioritizing based on application needs.




Yield Strength




What yield strength means:




Yield strength indicates the stress at which material begins to deform permanently (plastically). Design stresses typically stay below yield strength to ensure elastic behavior.




Yield strength comparison:




Grade	Minimum Yield Strength	Yield/Tensile Ratio
GGG50	320-350 MPa	0.64-0.70
GGG60	370 MPa	0.62
GGG70	420 MPa	0.60

Hardness




What hardness means:




Hardness indicates resistance to surface indentation and wear. Higher hardness improves wear resistance but may reduce machinability.




Hardness ranges by grade:




Grade	Brinell Hardness (HB)	Machinability	Wear Resistance
GGG50	170-240 HB	Good	Good
GGG60	200-260 HB	Fair	Very Good
GGG70	230-290 HB	Fair-Poor	Excellent
GGG80	250-320 HB	Poor	Outstanding

Machinability note: GGG40-50 machine easily with standard tooling. GGG60-70 may require carbide tooling and reduced cutting speeds.




Grade Selection by Application




GGG40 Applications




Best suited for:




Application	Rationale
Pipe fittings (low pressure)	Adequate strength, excellent ductility
Agricultural equipment parts	Impact loading from field operations
Hand tools and hardware	Toughness for occasional impact
Low-temperature applications	Maintains ductility at sub-zero temperatures
Components requiring cold forming	High elongation enables deformation

Typical specifications:

• Material: EN-GJS-400-18 per ISO 1083

• Heat treatment: As-cast or annealed

• Inspection: Visual, dimensional, hardness




GGG50 Applications




Best suited for:




Application	Rationale
Valve bodies (medium pressure)	Good pressure containment
Gearbox housings	Adequate strength for most loads
Compressor parts	Balanced properties for dynamic loading
Machine tool components	Good machinability with adequate strength
General engineering castings	Versatile grade for varied applications

Typical specifications:

• Material: EN-GJS-500-7 per ISO 1083

• Heat treatment: As-cast or normalized

• Inspection: Visual, dimensional, hardness, chemical




GGG60 Applications




Best suited for:




Application	Rationale
Gears and pinions	Surface hardness for wear resistance
Pressure vessels (higher pressure)	Enhanced strength for containment
Hydraulic components	Strength for high-pressure service
Rollers and rolls	Wear resistance for contact loading
Automotive suspension components	Strength for dynamic loads

Typical specifications:

• Material: EN-GJS-600-3 per ISO 1083

• Heat treatment: Normalized or quenched & tempered

• Inspection: Visual, dimensional, hardness, chemical, ultrasonic




GGG70 Applications




Best suited for:




Application	Rationale
Heavy-duty gears	Surface durability for high loads
Cutting and forming tools	Hardness for tool applications
Mining equipment parts	Abrasion resistance
High-strength structural parts	Maximum load capacity
Brake discs and drums	Wear resistance for friction service

Typical specifications:

• Material: EN-GJS-700-2 per ISO 1083

• Heat treatment: Quenched & tempered or austempered (ADI)

• Inspection: Full inspection including NDT




Heat Treatment Effects on Grades




As-Cast Condition




Characteristics:

• Lowest cost (no additional heat treatment)

• Properties vary with section thickness

• Suitable for GGG40-50 applications

• Typical hardness: 170-230 HB




Annealing




Purpose: Improve ductility and machinability




Grade	Typical Result
GGG50	Elongation 10-12%, hardness 160-210 HB

Applications: Components requiring cold forming or extensive machining.




Normalizing




Purpose: Increase strength and hardness




Grade	Typical Result
GGG60	Tensile 600-650 MPa, hardness 220-270 HB

Applications: Components requiring higher strength without quenching.




Quench and Temper




Purpose: Maximum strength and hardness




Grade	Typical Result
GGG70	Tensile 750-850 MPa, hardness 280-350 HB

Applications: High-stress, wear-resistant components.




Austempering (ADI)




Purpose: Create Austempered Ductile Iron with superior properties




ADI Grade Properties:




ADI Grade	Tensile Strength	Elongation	Hardness
Grade 2	1050 MPa	7%	302-363 HB
Grade 3	1200 MPa	4%	341-401 HB
Grade 4	1400 MPa	2%	388-444 HB

Applications: High-performance gears, crankshafts, wear parts.




Material Certification Requirements




Standard Certification




What to specify:




Document	Content	Typical Requirement
Certificate of Compliance	Statement of specification compliance	All orders
Heat Treatment Record	Heat treatment parameters and results	When heat treated
Hardness Test Report	Hardness values and locations	Critical applications

Testing Frequency




Standard testing per heat/batch:




Test	Frequency	Standard
Tensile testing	Per batch (typically per day)	ISO 6892
Hardness testing	Per batch or per heat	ISO 6506
Microstructure	When specified	ISO 945

Additional Testing for Critical Applications




Test	Application	Standard
Magnetic particle	Surface defect detection	ISO 9934
Impact testing	Low-temperature service	ISO 148
Metallography	Quality verification	ISO 945

Material Selection for Ductile Iron Applications




Material certification gaps cause more disputes than any other specification issue. Verifying grade capability before order placement prevents costly non-conformance and ensures mechanical properties match your application requirements. Tiegu provides visibility into actual supplier performance beyond certificates. We help international buyers navigate material selection with local expertise.




This helps buyers make informed sourcing decisions and reduces the risk of material-related failures.




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If you are unsure about material selection for your application, understanding the strength-ductility tradeoff is essential.




We help international buyers navigate China's casting supply chain with local expertise and structured sourcing processes.




You can contact Tiegu team to discuss your sourcing needs and get expert recommendations.




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Summary: Key Takeaways




1. Grade numbers indicate tensile strength — GGG40 = 400 MPa, GGG50 = 500 MPa, etc.

2. Higher strength = lower ductility — Cannot maximize both simultaneously

3. GGG40 for impact applications — Highest ductility (15-18% elongation)

4. GGG50 for general use — Best balance of strength and ductility

5. GGG60-70 for high-stress/wear — Higher strength, lower ductility

6. Heat treatment affects properties — Annealing improves ductility, hardening increases strength

7. Specify certification requirements — MTRs and test reports verify grade compliance




Further reading topics:

• Gray iron vs ductile iron: When to use each

• Understanding casting tolerances and machining allowances

• Heat treatment options for ductile iron castings




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