Gray Cast Iron Class 40 (ASTM A48)

Designations: A48 Class 40 · UNS F12801 · SAE J431 G4000ASTM A48 Class 40 is a high-strength gray cast iron, specified where a component needs more load capacity than Class 30 or 35 while keeping gray iron's machinability, vibration damping and dimensional stability. The class number is the minimum tensile strength in ksi, so Class 40 means 40 ksi. It suits machine tool beds, heavy housings, gear blanks and hydraulic bodies. Kormax casts A48 Class 40 to order for customers in the United States and Canada.

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Chemical Composition

Gray Cast Iron Class 40 — chemical composition, % by weight
Element	Symbol	Range / limit %
Carbon	C	2.9–3.2
Silicon	Si	1.5–2.0
Manganese	Mn	0.6–0.9
Phosphorus	P	0.15 max
Sulfur	S	0.12 max
Chromium	Cr	0.05–0.45
Nickel	Ni	0.05–0.20
Molybdenum	Mo	0.05–0.10
Iron	Fe	Balance

Mechanical Properties

Gray Cast Iron Class 40 — mechanical properties
Property	Metric	Imperial
Tensile Strength, min	276 MPa	40 ksi
Hardness (Brinell), typical	217–269 HB	217–269 HB

ASTM A48 specifies minimum tensile strength only; the class number is that minimum in ksi. Gray iron has no meaningful yield point or elongation. Hardness is typical (SAE J431 G4000 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.