Gray Iron
Overview
Dura-Bar continuous cast gray irons contain flake graphite in matrix structures that range from all pearlite to pearlite plus ferrite depending on the grades. The flake configuration corresponds to ASTM Type VII and is available in Type D, size 6-8 or Type A, size 4-6.
The matrix structure will influence machinability, strength, hardness and wear characteristics. In general, a fully pearlitic matrix will have the best mechanical properties and will be readily machinable. Bars containing ferrite in the matrix will be easier to machine but will be lower in strength and wear resistance.
| Iron | Stock Grades | Non-Stock Grades |
|---|---|---|
| Gray | G2, GX, G2P | N/A |
The graphite structure influences strength, surface finish and hardness.The most common gray iron specification will contain Type VII flakes, type A, size 4-6, as evaluated in ASTM A247. Dura-Bar G2 gray iron will contain this type of graphite distribution and will be best suited for applications requiring moderate strength, good vibration damping and thermal conductivity, along with optimal machining characteristics. Dura-Bar G2 is built around ASTM A48 Class 40 gray iron.
Dura-Bar G2P will have the same graphite distribution with a highly pearlitic core matrix and mostly pearlitic rim matrix aiding surface hardenability.
Gray Iron Grade Comparison
| Grade | Tensile Strength (psi min) | Fatigue Strength (psi) | Extended Sizes |
|---|---|---|---|
| G2 > | 40,000* | 20,000 | |
| GX > | 40,000* | 20,000 | Yes |
| G2P > | 40,000* | tbd |
* Gray iron tensile strengths are based on the strength of a cast test bar. For more information download our Dura-Bar ASTM A48 Policy tech brief. Gray iron will not yield/elongate before fracture. The behavior of gray iron is non-ductile.
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