Grey iron, commonly referred to as cast iron, is the most common of the cast iron alloys. Relatively cheap and easy to produce, grey iron finds its way into a number of engineering applications where strength and toughness are not the primary concern. The graphite present in grey iron exists in flake form, which is the primary physical difference when comparing grey, compacted graphite and ductile iron.

There are many different specifications governing the use and production of grey iron. At Smith Foundry, we produce grey iron in accordance with American Society of Testing and Materials (ASTM) A48. ASTM A48 covers a class of cast irons that are intended for general use applications.

Grades of ASTM A48 Grey Iron Produced at Smith Foundry

ASTM A48 Grade Ultimate Tensile Strength (UTS) Brinell Hardness
Class 30 30,000 p.s.i 187-241
Class 35 35,000 p.s.i. 207-255
Class 40 40,000 p.s.i 217-269

*UTS values are minimums required by ASTM for an independently cast tensile test bar sample. Casting strength may be more or less depending on cast section thickness. Consult ASTM A48 or Smith Foundry for more information.

Desirable properties Common Applications
Excellent vibration dampening capability Brake drums, rotors and clutch components
High compressive strength Engine blocks, cylinder liners and heads
Good machinability Pulleys, sheaves and idler wheels
Exceptional heat transfer Gears
Low cost alternative to other engineering materials Hydraulic valves and components






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Grey Iron