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? Nodular graphite inclusions dot its infrastructure, lending structural integrity that traditional cast iron (aka gray cast iron) does not have.
MECHANICAL PROPERTIES OF DUCTILE IRON Castings
Unlike the graphite flakes in gray cast 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 enhanced ductility, tensile and yield strength, heat dissipation, and vibration and sound-dampening properties than their gray cast iron counterparts.
THE DUCTILE IRON CASTING PROCESS
The higher the nodule count in 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 iron 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 cast iron.
ECONOMY
Ductile iron comes in at a significantly lower price point than cast steel, and only slightly more than gray cast 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, per the latest standards set forth by ASTM International.
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.
What is the difference between ductile iron and cast iron (aka gray iron)?
How is ductile iron better than steel?
What is ductile iron composed of?
What is austempered ductile iron (ADI)?
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