Technical guide · 2026-08-14
Ductile Cast Iron
Ductile iron uses spheroidal graphite to reduce crack-like stress concentration and provide useful yield strength and elongation, with matrix and heat treatment tailored from ferritic toughness to austempered strength.
01
Definition and boundary
Ductile iron is chosen for tensile and fatigue load capacity beyond gray iron; nodularity and matrix acceptance are part of the product definition.
Reference information only: final acceptance is controlled by the ordered product specification, condition, dimensions and certified test results.
02
How the material system works
Magnesium treatment produces spheroidal graphite.
Ferritic, pearlitic or austempered matrices set strength-ductility balance.
Heavy-section segregation can reduce nodularity and local properties.
03
Representative grades and systems
| Grade or system | Selection focus | Qualification |
|---|---|---|
| ASTM A536 65-45-12 | General ferritic-pearlitic balance. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| ASTM A536 80-55-06 | Higher strength with lower elongation. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| ASTM A897 Grade 1 | Austempered ductile iron requiring controlled heat treatment. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
04
Properties and trade-offs
Defined yield strength and elongation
Fatigue and impact capability
Pressure integrity with suitable foundry control
05
Product forms and supply conditions
06
Applications and selection
Applications and selection
- Gears and suspension parts
- Valve bodies and pressure fittings
- Wind-energy hubs and heavy castings
Properties and trade-offs
- Choose grade from load spectrum and minimum ductility.
- Review nodularity in the controlling section.
- Use ADI only with qualified machining and heat-treatment sequence.
07
Fabrication, durability and inspection
Machine ADI before austempering where practical.
Control magnesium fade and inoculation.
Avoid weld repair unless procedure and property restoration are qualified.
08
Procurement checklist
- State grade, heat treatment and nodularity requirement.
- Locate test coupons relative to controlling section.
- Define NDT, impact, hardness and pressure tests as needed.
09
Standards, sources and review
Standards and designation context
- Applicable ASTM A04 iron-casting specification
- Buyer drawing and foundry process qualification
- Agreed test-coupon and inspection standard