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Iron Types: Ductile and Gray


Iron Types:
Ductile and Gray

Gartland Foundry produces customers' products in two major iron types: Ductile and Gray.

The choice of metal depends on customers' various design requirements for their product and the environment in which it will be used.


Ductile Iron Castings

Ductile iron is often used as a cost effective alternative to steel castings. Ductile iron improves the resistance to cracking which may occur in gray iron and ductile iron may be able to reduce overall dimensions and mass of a casting without sacrificing performance characteristics. Ductile iron provides high tensile strength, with improved ease of machining, vibration damping, surface hardening, and resistance to damage from impact, corrosion resistance and wear resistance, all at a competitive price. Relative to gray iron, ductile iron provides an improved strength-to-weight ratio, resistance to impact, corrosion and wear resistance, with an improved modulus of elasticity.

Common use of ductile iron is in assembly parts for the auto and agricultural industries, such as flanges, gears, hubs, suspension parts, and in the flow control industry, such as for valves, meters and pumps.

Typical ductile iron classes, designated by ASTM A536 are:

Class Tensile Strength
Brinell Hardness
Elongation %
(in 2 inches)
100-70-30 100,000 228 - 302 3
80-55-06 80,000 187 - 255 6
65-45-12 65,000 156 - 217 12
60-40-18 60,000 156 - 187 18

Ductile iron castings may be austempered, producing structures of acicular ferrite and high carbon structures, to achieve specific mechanical properties. Austempering is accomplished by maintaining the casting at the quenching temperature for an extended period of time. The casting is then cooled rapidly to avoid formation of pearlite structures.

For additional information on ductile iron: Ductile Iron Society:

Gray Iron Castings

Gray iron is an alternative for economical, castable products with ease of machining. Relative to cast steel, gray iron provides improved surface hardenability, vibration damping, castability, corrosion and wear resistance and at a lower cost to manufacture.

Common applications of gray iron are similar to ductile iron, and specifically where complex design is required or other engineering design considerations by the customer that do not require high tensile strength or ductility. Examples of products using gray iron: engines, motor casings and machine tools. Gray iron provides an excellent sliding surface, resists galling and seizing. Heat treatment may be used to increase hardness.

Typical gray iron classes, designated by ASTM A48 are:

Class Tensile Strength (psi) Brinell Hardness Range
25 25,000 149 - 229
30 30,000 187 - 241
35 35,000 207 - 255
40 40,000 217 - 269

Ductile and gray iron products may both be coated, painted and machined to meet specific design requirements.

For Additional Information on Ductile and Gray Iron and Foundries:


Ductile Iron:
Gray Iron:
Iron Foundry:
Sand Casting:
Core Making:
Sand Testing:


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Gartland Foundry
330 Grant Street
Terre Haute, Indiana 47802 USA

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Phone: 812.232.0226
Business Hours: 8am - 5pm EST