Technical guide · 2026-08-14
Malleable Cast Iron
Malleable iron is produced by prolonged heat treatment of white-iron castings to form temper carbon, providing ductility and machinability in relatively small, controlled-section fittings and hardware.
01
Definition and boundary
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.
Reference information only: final acceptance is controlled by the ordered product specification, condition, dimensions and certified test results.
02
How the material system works
White-iron castings provide a carbon source without graphite flakes.
Annealing decomposes carbides into temper-carbon aggregates.
Matrix control produces ferritic or pearlitic property sets.
03
Representative grades and systems
| Grade or system | Selection focus | Qualification |
|---|---|---|
| ASTM A47 Grade 32510 | Ferritic malleable iron for ductility-led service. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| ASTM A220 Grade 50005 | Pearlitic malleable grade with higher strength. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
| EN-GJMB-350-10 | Blackheart malleable designation with its own acceptance basis. | Confirm the governing product specification, delivery condition, section size and acceptance tests before treating designations as interchangeable. |
04
Properties and trade-offs
Useful ductility in small castings
Good machinability
Reliable threaded and shock-loaded hardware performance
05
Product forms and supply conditions
06
Applications and selection
Applications and selection
- Pipe fittings
- Brackets and hand tools
- Electrical and agricultural hardware
Properties and trade-offs
- Check section limits for complete annealing.
- Choose ferritic versus pearlitic matrix by load and machining.
- Compare lifecycle and tooling against ductile-iron alternatives.
07
Fabrication, durability and inspection
Maintain anneal time and atmosphere uniformity.
Prevent residual carbide in heavy sections.
Control thread machining and plating preparation.
08
Procurement checklist
- State ferritic or pearlitic specification and grade.
- Define section range and heat-treatment lot.
- Specify hardness, elongation, threads and coating acceptance.
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