Gray Cast Iron Class 25 (ASTM A48)

Designations: A48 Class 25 · UNS F11701 · SAE J431 G2500ASTM A48 Class 25 is a gray cast iron that pairs good machinability and vibration damping with moderate strength, a step up from Class 20 for parts that carry some load. The class number is the minimum tensile strength in ksi, so Class 25 means 25 ksi. It suits housings, covers, pulleys and general machinery castings. Kormax casts A48 Class 25 to order for customers in the United States and Canada.

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Chemical Composition

Gray Cast Iron Class 25 — chemical composition, % by weight
Element	Symbol	Range / limit %
Carbon	C	3.0–3.5
Silicon	Si	1.4–2.0
Manganese	Mn	1.0–1.7
Phosphorus	P	0.15 max
Sulfur	S	0.12 max
Chromium	Cr	0.05–0.45
Nickel	Ni	0.05–0.10
Molybdenum	Mo	0.05–0.10
Copper	Cu	0.15–0.40
Iron	Fe	Balance

Mechanical Properties

Gray Cast Iron Class 25 — mechanical properties
Property	Metric	Imperial
Tensile Strength, min	172 MPa	25 ksi
Hardness (Brinell), typical	170–229 HB	170–229 HB

ASTM A48 specifies minimum tensile strength only; the class number is that minimum in ksi. Hardness is typical (SAE J431 G2500 range) and varies with section size. Composition is Kormax typical foundry practice, not specified by ASTM A48.

Comparable and Related Specifications

The standards and grades below may have similar composition, properties or applications, but they should not be treated as direct equivalents without review. Chemistry, heat treatment, toughness requirements and testing provisions can differ between standards.