ASTM A48 Class 40 Gray Iron

ASTM A48 / Class 40. A48 Class 40 is a medium-high strength gray cast iron (276 MPa / 40 ksi minimum tensile) with excellent machinability, vibration damping and wear resistance.

Chemical composition (nominal wt %)

Element%
Carbon (C)3.1–3.4
Silicon (Si)1.9–2.3
Manganese (Mn)0.6–0.9
Sulfur (S)≤0.15
Phosphorus (P)≤0.15

Mechanical properties

PropertyValue
Tensile strength276 MPa (40 ksi) min
Yield strength— (no defined yield, brittle)
Elongation<1%
Hardness201–255 HB

Density: 7.2 g/cm³  ·  Heat treatment: Generally used as-cast; stress-relief anneal at 540–565 °C for dimensional stability.

Cross-standard equivalents

StandardEquivalent grade
EN / ISOEN-GJL-300
GBHT300
JISFC300
DIN (old)GG30

Equivalents by nominal class — confirm exact chemistry & spec for critical parts.

Typical applications

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FAQ

What does ASTM A48 Class 40 mean?

Gray cast iron with a minimum tensile strength of 40,000 psi (~276 MPa). In ASTM A48 the class number equals the minimum tensile strength in ksi.