Advantages Of Ductile Iron

Why Ductile Iron?

Ductile Iron not only retains all of Gray Iron’s attractive qualities, such as machinability and corrosion resistance, but also provides
 additional strength, toughness, and ductility. Although its chemical properties are similar to those of Gray Iron, Ductile Iron incorporates
 significant casting refinements, additional metallurgical processes, and superior quality control.

Ductile Iron also differs from Gray Iron in that its graphite form is spheroidal, or nodular, instead of the flake form found in Gray Iron.
This change in graphite form is accomplished by adding an inoculant, usually magnesium, to molten iron of appropriate composition during manufacture.
Due to its spheroidal graphite form, Ductile Iron has approximately twice the strength of Gray Iron as determined by tensile, beam,ring bending, and bursting tests. Its impact strength and elongation are many times greater than Gray Iron’s.
As these photomicrographs show, Ductile Iron (above left) differs from Gray Iron (above right) in that
its graphite is spheroidal, or nodular, instead of the flake form found in Gray Iron. Ductile’s greater
strength, ductility, and toughness are due to this change in microstructure.
Ductile Iron Gray Iron

Ductile Iron Advantages:

Exhibits Tremendous Tensile Strength
 A pipe must be able to withstand severe stresses caused externally by shifting ground and heavy loads and internally by water pressure and water hammer. Ductile Iron has minimum strength requirements of 60,000 psi tensile strength,42,000 psi yield strength, and 10 percent minimum elongation

Withstands Severe Crushing Loads
Extreme traffic loads, heavy backfill, or earth movements caused by freezing, thawing, and soil swell pressures
impose tremendous forces on buried pipes. Beam tests, free bend tests, and toughest of all ring tests, which
determine the pipe’s ability to resist concentrated loads, all demonstrate the superiority of Ductile Iron pipe

Has Great Beam Strength
Ductile Iron will bend or give considerably before it will ultimately fail. This characteristic is what makes its ductility so desirable.
Ductile Iron’s ability to bend under load greatly increases its resistance to beam load. 

Is Corrosion Resistant
Numerous laboratory and field tests have proven that Ductile Iron’s corrosion resistance is equal to or greater than that
of Gray Iron, which has served a number of U.S. utilities for more than 150 years with no external corrosion protection.
In the majority of soils, Ductile Iron needs no external corrosion protection. In most areas of highly corrosive soil,
simple, economical polyethylene encasement has provided excellent corrosion protection for the pipe. 

Has Extremely High Impact Resistance
In test after test, Ductile Iron has exhibited tremendous impact resistance. Ductile’s toughness makes it much less
vulnerable to damage from improper handling or abnormal service conditions. And it stands up under heavy traffic
conditions in unstable soil environments where other materials might fail due to the stresses caused by unusual loading. 

Demonstrates Tremendous Bursting Strength
Ductile’s tremendous bursting strength makes it ideally suited for high-pressure applications. Six-inch Pressure Class
350 Ductile Iron, for example, has a bursting pressure exceeding 3,500 psi. Ductile’s bursting strength also provides
an additional safety factor against water hammer. 

Is Easy to Install
Ductile Iron is easy to install in the field. A wide variety of joints and standard fittings are available for every application.<
Ductile Iron can be cut and direct tapped in the field. And it requires no complex laying schedules or line-and-grade drawings 

Is Virtually Maintenance Free
Years of experience in operating systems throughout the world have proven that, once installed, Ductile Iron requires
little, if any, maintenance over the life of the pipeline. Ductile’s longevity can be witnessed in the outstanding service
records of Gray Iron pipe over the past 150 years. 

Offers Impressive Energy Savings
Ductile’s high flow coefficient (C=140) and generally larger-than-nominal inside diameters can result in increased
flow capacity, lower head loss, lower pumping costs, and significant energy savings over the life of the pipeline. 

 


 

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