Ductile iron — sometimes also referred to as ductile cast iron, nodular (cast) iron, spheroidal graphite (cast) iron, or SG (cast) iron — has been an industry favorite since its invention in the 1940s and gradual refinement in the '50s, '60s, and beyond. The reason? The spheroidal graphite nodules dotting its infrastructure, lending structural integrity that regular cast iron (aka gray iron) does not have. 

MECHANICAL PROPERTIES OF DUCTILE IRON

Unlike the graphite flakes in gray iron, spheroidal graphite holds ductile iron together without fracturing as it bends and acts as a built-in buffer against wear. This results in products with greater ductility, tensile and yield strength, heat dissipation, and vibration and sound dampening properties than their gray iron counterparts.

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casting ductile iron

THE DUCTILE IRON CASTING PROCESS

The higher the nodule count in a ductile iron casting, the better its strength and elongation properties. At Urick Foundry, we achieve consistently high nodule counts through vertical in-mold inoculation. In this method, molten metal is inoculated with magnesium as it's poured into each mold, ensuring uniform distribution both within the mold and between molds. Our proprietary vertical casting process minimizes gas bubbles and other structural deficiencies, while consistently producing nodularities of 85% or better — far exceeding industry standards.

BENEFITS OF DUCTILE IRON CASTINGS

FLEXIBILITY

Ductile iron offers flexibility both in its physical properties and from a design standpoint. Its castability, machinability, and ability to elongate and deform without fracture are far beyond gray iron.

ECONOMY

Ductile iron comes in at a significantly lower price point than cast steel, and only slightly more than gray iron. However, its overall performance and wear resistance make it a cost-effective solution.

STRENGTH

Ductile iron is an exceptionally resilient material in terms of both yield strength and tensile strength,  meaning it can withstand immense physical stress without changing shape or breaking.

SAE J434 DUCTILE CAST IRON GRADES PRODUCED BY URICK

Urick produces ductile iron castings in accordance with the latest SAE J434 standards for hardness, strength, and elongation. 

Grade Typical BHN Tensile Strength (min) Yield Strength (min) % Elongation
MPa KSI MPa KSI
D400 143-170 400 58 275 40 18
D450 156-217 450 65 310 45 12
D500 187-229 500 73 345 50 6
D550 217-269 550 80 380 55 4
D700 241-302 700 102 450 65 3
D800 255-311 800 116 480 70 2

ASTM A897 / 897M-06 Austempered Ductile Iron

Austempering is a heat treatment process that enhances the hardness and toughness of ductile iron. Urick is capable of providing various grades of austempered ductile iron (ADI) castings through our trusted partner Applied Process, in accordance with the latest standards set forth by ASTM International. 

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FREQUENTLY ASKED QUESTIONS

What is ductile iron?

Ductile cast iron is iron that has been treated with magnesium and other elements to enhance its ductility, or ability to stretch when tensile force is applied. A ductile metal is better able to be pulled or bent in various directions while resisting snapping or breaking.

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