CI · cast iron
Ductile Iron GGG40 (EN-GJS-400-15, 60-40-18)
Ductile iron with the graphite in nodules rather than flakes: it has real elongation, it takes impact, and it machines like a soft steel with better chip control than grey iron.
Quoting this material
- Typical lead time
- 15–25 working days
- Condition
- As cast, or normalised; annealed for maximum ductility
- Achievable finish
- Ra 1.6 µm typical · Ra 0.8 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
Ductile iron with the graphite in nodules rather than flakes: it has real elongation, it takes impact, and it machines like a soft steel with better chip control than grey iron.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 400 | MPa |
| Yield strength (0.2%) | 250 | MPa |
| Elongation | 15 | % |
| Hardness | 160–210 | HB |
| Impact resistance | Real, unlike grey iron | - |
| Modulus of elasticity | 170 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
As cast, or normalised; annealed for maximum ductility
Heat treatment
Can be normalised or annealed to adjust the matrix, and it can be austempered to make ADI. The standard 400-15 condition is annealed for ductility, which is what the 15% elongation figure comes from.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Machines to a cleaner surface than grey iron because the nodular graphite does not smear the same way.
Tooling and cutting parameters
Cutting speed
- 150–300 m/min (carbide)
Feed
- 0.15–0.35 mm/rev turning · 0.10–0.25 mm/tooth milling
Tooling
- Coated carbide; the nodular structure cuts like a soft steel
Coolant
- Flood or mist; ductile iron machining produces fewer fine dust particles than grey iron
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Hydraulic valve and pump bodies
- Pipes and fittings for water service
- Machine frames subject to shock
- Automotive suspension castings
- Wind turbine and heavy machinery hubs
DFM notes for this grade
- Ductile iron is the material where a casting has to take impact or a pressure: it has elongation and a real yield point where grey iron has neither
- It machines more like steel, so the feeds and speeds sit between grey iron and a low carbon steel, and chip control is better
- Where a pressure-tight casting is needed, ductile iron is far more reliable than grey iron - grey iron porosity is the usual source of a leaking housing
Questions buyers ask
- What is the difference between grey and ductile iron?
- The shape of the graphite. In grey iron the graphite is flakes, which are sharp internal discontinuities and make the material brittle. In ductile iron it is nodules, which do not concentrate stress - hence 15% elongation against essentially none, and a material that can take impact.
- Does ductile iron machine differently from grey iron?
- Yes: it forms a chip rather than a dust, and it cuts more like a soft steel. That means better surface finish and easier chip control, with slightly more tool pressure. It also means the dust control problem that dominates grey iron machining is much reduced.
Grades we would quote instead
GGG60 / Ductile Iron 600-3
5/10A high-strength ductile iron: 600 MPa with 3% elongation.
GJL250 (Grey Iron 250)
7/10Grey iron cuts cleanly and dry: the graphite flakes act as a built-in chip breaker and lubricant, so it machines fast, throws dust instead of chips, and wears the ways if the dust is not contained.
ADI (Austempered Ductile Iron)
3/10Ductile iron put through an austempering heat treatment to reach 800–1,100 MPa.