When should ductile iron be specified instead of cast steel?

Ductile iron offers: (1) 10-15% lower density than cast steel (7.10 vs 7.85 g/cm³) — lighter components for equal volume; (2) superior castability — lower pouring temperature (~1400°C vs ~1600°C for steel), better fluidity filling thin sections, lower shrinkage requiring smaller risers; (3) graphite provides natural lubricity (excellent for sliding wear applications like gears and cylinder liners); (4) better vibration damping than steel. Cast steel (e.g., ASTM A958 Grade SC 450 or 8620 investment cast) is preferred when: (1) welding to a steel structure is required (ductile iron welds are prone to heat-affected-zone carbide formation and cracking); (2) low-temperature impact properties below -40°C are needed (ductile iron has a ductile-to-brittle transition; cast austenitic stainless steel may be required); (3) the part will be hot-dip galvanized (ductile iron's graphite can cause coating adhesion issues).

Ductile Iron 65-45-12 (ASTM A536): Hoch-Impact Nodular Cast Iron für Structural Castings

ASTM A536 / ISO 1083 JS/500-7 / EN-GJS-500-7 · Published: 2026-05-31 · Updated: July 2026

Quick Reference

Ductile iron 65-45-12 is the most versatile grade of ductile (nodular) cast iron, offering a combination of strength, ductility (12% minimum elongation), and castability unmatched by competing cast metals in its price range. The '65-45-12'...

Ductile iron 65-45-12 ist der meiste versatile grade von ductile (nodular) cast iron, offering ein combination von strength, ductility (12% minimum elongation), und castability unmatched durch competing cast metals in sein preis bereich. Der '65-45-12' designation follows ASTM A536: 65 ksi minimum tensile strength, 45 ksi minimum yield strength, 12% minimum elongation. Ductile iron achieves sein properties durch magnesium oder cerium treatment von molten base iron, causing graphite zu precipitate als spheroids (nodules) rather als flakes als in gray iron. Der spheroidal graphite morphology eliminates der notch-effect stress concentrations von flake graphite, enabling ductility und impact widerstand impossible in gray iron.

Quick Facts

Kategorie	Cast Iron
Norm	`ASTM A536 / ISO 1083 JS/500-7 / EN-GJS-500-7`
Density	7.10 g/cm³
Yield Strength	310 MPa (45 ksi) minimum
Tensile Strength	448 MPa (65 ksi) minimum

Detailed Mechanical Properties

Elongation	12% minimum
Härte	156-217 HB
Streckgrenze	310 MPa (45 ksi)
Zugfestigkeit	448 MPa (65 ksi)

Physical Eigenschaften

Schmelzpunkt	1150-1200°C
Wärmeleitfähigkeit	36 W/m·K bei 20°C
Dichte	7.10 g/cm³

Global Equivalents & Cross-Referenz

Alternative Norm / Güte	Action
EN-GJS-500-7	Compare
ISO 1083 500-7	Compare
JIS FCD500-7	Compare
GB QT500-7	Compare
DIN GGG-50	Compare

Heat Treatment & Processing

Annealing	870-900°C, halten 1h/25mm, furnace cool zu 540°C, dann luft cool
Normalizing	870-900°C, luft cool
Stress Relieving	510-565°C, 1h/25mm
Hinweis	65-45-12 = 65 ksi tensile, 45 ksi yield, 12% elongation. Ferritic grade mit spheroidal graphite nodules. Gut machinability und impact widerstand.

Welding & Fabrication

Preheat	200-300°C für alle thicknesses
Filler Metal	ENiFe-CI oder ENi-CI (nickel-based electrodes für cast iron)
Pwht	Slow cool zu room temperature — wrap in insulating blanket oder bury in dry sand
Schweißeignung Rating	Fair — cast iron welding ist immer challenging. Nickel-based filler reduces cracking risk but full strength restoration ist nicht möglich.

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Frequently Asked Questions

Wenn sollte ductile iron sein specified instead von cast steel?

Ductile iron offers: (1) 10-15% unter density als cast steel (7.10 vs 7.85 g/cm³) — lighter components für equal volume; (2) superior castability — unter pouring temperature (~1400°C vs ~1600°C für steel), better fluidity filling thin sections, unter shrinkage requiring smaller risers; (3) graphite provides natural lubricity (excellent für sliding wear applications wie gears und zylinder liners); (4) better vibration damping als steel. Cast steel (e.g., ASTM A958 Güte SC 450 oder 8620 investment cast) ist preferred wenn: (1) welding zu ein steel structure ist erforderlich (ductile iron welds sind prone zu heat-affected-zone carbide formation und cracking); (2) niedrig-temperature impact properties unter -40°C sind needed (ductile iron hat ein ductile-zu-brittle transition; cast austenitic stainless steel kann sein erforderlich); (3) der teil werden sein heiß-dip galvanized (ductile iron's graphite können cause coating adhesion issues).

References & International Standards

ASTM International. Norm Specifications für Stahl & Metal Alloys. astm.org
International Organization für Standardization (ISO). Metallic Materials — Cross-Referenz Database. iso.org
American Iron und Stahl Institute (AISI). Stahl Güte Designations & Equivalents. steel.org
European Committee für Standardization (CEN). EN Stahl Standards & Numbering System. cencenelec.eu