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Gray Iron Castings

Gray iron commonly referred to as cast iron derives its name from the dull gray color of the surface when fractured. The graphite microstructure of gray iron is flaked, making this material suitable for applications requiring:

  • Complex shapes-excellent castability

  • Good machinability

  • Good tensile strengths

  • Good wear resistance

  • High vibration-dampening properties

  • High thermal conductivity

  • Excellent compressive strength

Gray irons are generally considered lower to moderate strength, with tensile ranges from 20,000 to 60,000 psi.

J.R. Hoe produces the following types of gray iron:


  • Class 25

  • Class 30

  • Class 35

  • Class 40

ASTM A319 (Gray iron for elevated temperatures)

This grade of iron is used in non-pressurized high temperature applications. Typically, the classes of ASTM A48 specification apply to this iron also. The class 35 of the ASTM A48 specification is used where tensile strength is not specified.