Reviewed · 2026-08-13
Cast Iron
Cast irons are iron-carbon-silicon casting alloys classified by graphite shape, matrix and heat treatment; these structural features determine machinability, damping, strength, ductility, thermal response and wear behavior in finished castings.
Classification basis
Graphite morphology, matrix, heat treatment, section response and governing casting specification
Five procurement categories distinguish flake, spheroidal, compacted and temper-carbon graphite from carbide-rich white and alloyed irons.
A familiar grade name never replaces the governing product specification and certified documentation.01
Explore subcategories
Gray Cast Iron
Use gray iron where compressive capacity, damping, thermal behavior or machinability matter more than tensile elongation and impact resistance.
→Cast ironDuctile Cast Iron
Ductile iron is chosen for tensile and fatigue load capacity beyond gray iron; nodularity and matrix acceptance are part of the product definition.
→Cast ironCompacted Graphite Iron
CGI is not merely high-strength gray iron; its compacted graphite percentage and nodularity ceiling must be demonstrated for the represented casting section.
→Cast ironMalleable Cast Iron
Malleable iron is a heat-treated casting route distinct from as-cast ductile iron and is most practical for smaller parts whose section can be converted reliably.
→Cast ironWhite and Alloyed Cast Iron
This group covers wear- and service-alloyed cast irons, not general gray or ductile components; grade must follow the actual abrasion, impact, corrosion and temperature regime.
→02
Representative grades and systems
| Grade / system | Use as a selection entry point |
|---|---|
| ASTM A48 Class 30 | Select graphite form around dominant load and thermal function. |
| ASTM A536 65-45-12 | Relate coupon results to controlling casting section and heat treatment. |
| ASTM A842 CGI | Put microstructure and supplemental inspection on the order when function demands them. |
| ASTM A47 malleable iron | Select graphite form around dominant load and thermal function. |
| Ni-Hard | Relate coupon results to controlling casting section and heat treatment. |
03
Property framework
Casting-section mechanical response
Damping, thermal conductivity and machinability
Ductility, fatigue or abrasion resistance by microstructure
04
Common product forms
05
Applications
- Machine bases and housings
- Powertrain, pump and piping components
- Wear liners, rolls and thermal-duty castings
- Select graphite form around dominant load and thermal function.
- Relate coupon results to controlling casting section and heat treatment.
- Put microstructure and supplemental inspection on the order when function demands them.
06
Standards and designation systems
ASTM A48 gray iron
ASTM A536 ductile iron and ASTM A842 compacted graphite iron
Application-specific ASTM, EN or ISO casting specifications
07
Procurement checklist
- State casting specification, grade and drawing revision.
- Define test-coupon type, controlling section and heat treatment.
- Specify microstructure, NDT, pressure tightness, machining stock and traceability.
08