Cast iron

Iron with 2–4 % carbon, cast to shape. In grey iron the graphite forms flakes; in ductile (nodular) iron it forms spheres, which makes it tough. The designation states the minimum tensile strength, and for ductile iron also the elongation.

Where it is used

Machine beds, frames and gearbox housings (grey iron)
Water and gas pipes, valves and fittings (ductile iron)
Crankshafts, brackets and manhole covers

Strengths

Complex shapes in one casting
Grey iron damps vibration and machines easily
Ductile iron combines castability with steel-like toughness

Limitations

Grey iron is brittle in tension
Strength falls with the wall thickness of the casting
Hard to weld

Typical values: EN-GJS-400-15

EN 1563

Tensile strength Rm: ≥ 400 MPa; guaranteed minimum; 1
0.2 % proof strength Rp0.2: ≥ 250 MPa; guaranteed minimum; 1
Elongation after fracture A: ≥ 15 %; guaranteed minimum; —

What engineers ask about cast iron

Does the wall thickness matter?

Yes. The grade value applies to a separately cast test piece; thicker walls cool more slowly and are weaker. For grey iron one supplier gives 155–250 MPa in castings for EN-GJL-250.

Not yet sourced: The EN 1561 and EN 1563 tables by relevant wall thickness are not yet sourced here.

— Sources

No authoritative or established source states this value yet.

Also stated by trade or aggregator pages (shown, not counted):

1
Marks GmbH — Technisches Datenblatt 0.6025, EN-GJL-250 (GG25) · Durchschnittswerte, Rm
Trade or aggregatorDistributorRead in full · 2 Nov 2026

Cast iron grades

Grey and ductile cast iron (EN 1561, EN 1563) for housings, machine beds, pipes and valves.

Standard fromAnywhere

CEN

Grey cast iron (EN 1561)

Flake graphite: easy to cast and machine, damps vibration, strong in compression, brittle in tension. Strength in a casting falls with wall thickness.

Grade	Standard	Tensile strength	Elongation after fracture	Evidence
EN-GJL-250 Grey cast iron for housings and machine beds: Rm 250 MPa minimum on the test piece, less in thick walls; brittle, damps vibration.	EN 1561	≥ 250 MPa1	0.3–0.8 %—	Single source 1 Trade sources only 2

Ductile (nodular) cast iron (EN 1563)

Spheroidal graphite gives steel-like ductility. The designation EN-GJS-400-15 states Rm 400 MPa and 15 % elongation.

Grade	Standard	Tensile strength	Elongation after fracture	Evidence
EN-GJS-400-15 Ferritic ductile iron: Rm 400 MPa, Rp0.2 250 MPa, elongation 15 % — castable like iron, tough like steel.	EN 1563	≥ 400 MPa1	≥ 15 %—	Single source 2 Trade sources only 6

Planned groups

EN-GJS-500-7, EN-GJS-600-3, low-temperature EN-GJS-400-18-LT
EN-GJL-200 and EN-GJL-300; austempered ductile iron (EN 1564)

Standards for cast iron

All standards for cast iron