CI · cast iron
Ductile Iron GGG70 (EN-GJS-700-2)
The top of the standard ductile iron range: 700 MPa with 2% elongation. Machining sits between a medium carbon steel and a low alloy steel - expect real tool consumption.
Quoting this material
- Typical lead time
- 18–28 working days
- Condition
- As cast or normalised; often surface hardened for wear surfaces
- 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.
The top of the standard ductile iron range: 700 MPa with 2% elongation. Machining sits between a medium carbon steel and a low alloy steel - expect real tool consumption.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 700 | MPa |
| Yield strength (0.2%) | 420 | MPa |
| Elongation | 2 | % |
| Hardness | 240–300 | HB |
| Wear resistance | High for a cast 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; often surface hardened for wear surfaces
Heat treatment
Normalised for the pearlitic matrix. Surface hardening by induction or flame after rough machining is common where the part is a wear surface.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Finishes well but slowly; the hardness puts it in the class where the finishing pass is planned rather than assumed.
Tooling and cutting parameters
Cutting speed
- 80–180 m/min (carbide)
Feed
- 0.12–0.25 mm/rev turning · 0.06–0.15 mm/tooth milling
Tooling
- Coated carbide with a tough substrate; CBN for a hardened surface
Coolant
- Flood
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
- Heavy-duty gears and pinions
- Rolls and wear rings
- Mill and crusher components
- Rail and transit brake parts
- High-load machine components
DFM notes for this grade
- It is near the practical ceiling for a machinable cast iron: beyond this, ADI or a forged and heat-treated steel is the answer
- 2% elongation makes it brittle in engineering terms - a casting defect or a sharp corner is a crack, and the part is not inspectable by any economic means for that
- Where the drawing calls for both wear resistance and machinability, consider GGG60 with an induction-hardened wear face instead of a through-hard GGG70
Questions buyers ask
- What is the practical limit of ductile iron?
- Around 700–900 MPa depending on the grade, and by the top of that range the elongation has gone and the machinability has dropped to that of a medium alloy steel. Beyond it, ADI or a heat-treated steel becomes the better engineering and economic choice.
- Should a GGG70 part be hardened at the surface?
- Only if the wear is local. A through-hard GGG70 part is already hard throughout; induction hardening a specific face gives far more wear resistance on that face without making the whole casting more difficult and more brittle.
Grades we would quote instead
GGG60 / Ductile Iron 600-3
5/10A high-strength ductile iron: 600 MPa with 3% elongation.
ADI (Austempered Ductile Iron)
3/10Ductile iron put through an austempering heat treatment to reach 800–1,100 MPa.
GJL300 (Grey Iron 300)
6/10The strongest of the standard grey irons: harder matrix, slightly tougher on the tool and still cutting clean and dry like its family.