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The Family of Ductile Irons

The majority of Ductile Iron castings are produced in one of the following three types, all of which can be produced in the as-cast condition without the need for heat treatment.

FERRITIC DUCTILE IRON (60-40-18)

Graphite spheroids in a matrix of ferrite which is basically pure iron. High impact resistance. Relatively good thermal conductivity. High magnetic permeability. Low hysteresis loss. In some exposures, good corrosion resistance. Good machinability.

PEARLITIC-FERRITIC DUCTILE IRON (80-55-06)

Graphite spheroids in a mixed matrix of ferrite and pearlite. This is the most common grade of Ductile Iron. Properties are between those with "fully ferritic" or "fully pearlitic" structures. Good machinability. Usually the least expensive Ductile Iron.

PEARLITIC DUCTILE IRON (100-70-03)

Graphite spheroids in a matrix of pearlite. Pearlite is a fine aggregate of ferrite and cementite (Fe3C). Relatively hard. Moderate ductility. High strength. Good wear resistance. Moderate impact resistance. Somewhat reduced thermal conductivity. Low magnetic permeability. High hysteresis loss. Good machinability.

MATRIX

Ferric
Grade 60-40-18

Ferric-
pearlitic
Grade 80-55-06

Pearlitic
Grade 100-70-03

Martensitic
(With retained austenite)

Tempered Marten-
sitic

ADI
Grade
150-100-7

ADI
Grade
230-185--

Austenitic

60000 psi
414 mPa

80000 psi
552 mPa

100000 psi
690 mPa

N.A. *

115000 psi
793 mPa

150000 psi
1050 mPa

230000 psi
1600 mPa

45000 psi
310 mPa


*Approximate ultimate tensile strength 87,000 psi (600 mPa) Hard, Brittle
(Note that the magnifications are different)

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