Gray Cast Iron Class 20 (ASTM A48)

Designations: A48 Class 20 · UNS F11401ASTM A48 Class 20 is the softest and most machinable of the gray cast irons, specified where damping and dimensional stability matter more than strength. Its coarse flake graphite structure absorbs vibration better than any higher class, which is why it persists in machine tool bases and enclosures long after stronger irons became available. It suits housings, covers, counterweights and manifolds. Kormax casts A48 Class 20 to order.

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Chemical Composition

Gray Cast Iron Class 20 — chemical composition, % by weight
Element	Symbol	Range / limit %
Carbon	C	3.25–3.5
Manganese	Mn	0.5–0.9
Silicon	Si	1.8–2.3
Nickel	Ni	0.05–0.20
Copper	Cu	0.15–0.40
Chromium	Cr	0.05–0.45
Molybdenum	Mo	0.05–0.10
Sulfur	S	0.15 max
Phosphorus	P	0.20 max
Iron	Fe	Balance

ASTM A48 specifies mechanical properties only. This is Kormax’s typical foundry composition.

Mechanical Properties

Gray Cast Iron Class 20 — mechanical properties
Property	Metric	Imperial
Tensile Strength, min	138 MPa	20 ksi
Hardness (Brinell)	156 HB	156 HB

Hardness is a typical value. ASTM A48 specifies tensile strength only. Rows To Delete Delete the Yield Strength and Elongation rows currently on this page. Gray iron has no defined yield point and elongates under 1%; the published 9.6% is not a gray iron figure. Class 35 on this site already has the correct two-row shape.

Got the numbers you needed? Kormax pours A48 Class 20 in chemically bonded sand, green sand and shell mold casting.

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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.

ASTM / SAE: ASTM A48 Class 20 / G9H12
UNS: F11401
Afnor: Ft15D
EN (EU/US): EN-GJL-150
DIN: GG15
BS (British Standard): Grade 150
GB (Chinese Standard): HT150