Gray Iron (Gray Cast Iron )

Carbon ranges from 2.5 to 4% and silicon from 1 to 3 percent by weight in gray cast iron. The element in the alloy is a need for the graphite molecules in gray cast iron to remain stable. This Silicon only works if the metal does not undergo thermal shock when it cools. Even with the inclusion of Silicon, very rapid cooling causes cementite. This is to form and makes gray iron white steel.

Gray Iron (Gray Cast Iron )

Ductile iron contains 3.2–3.6 percent carbon, 2.2–2.8 percent silica, and a minor amount of a nodulizing element. Graphite serves an important function in the microstructure of ductile iron, much like gray cast iron.  The nodulizing elements are magnesium, cerium, or tellurium. These form tiny spherical bodies around the graphite molecules,  instead of flaking away like gray cast iron. The nodules improve ductile iron’s flexibility and hardness while lowering its surface hardness.

Grey Iron VS Ductile Iron: The Difference Between Gray Iron And Ductile Iron

  • Formation Of Process

The formation of these two types of iron happens by adding carbon to hot beds. But in the case of Ductile Iron, there’s an addition of magnesium.

  • Graphite Structure

Graphite in Grey Iron has a rod-like or flaky pattern. Whereas graphite in Ductile Iron is nodular or spherical.

  • Ductility

Ductility is a property of graphite obtained by heating nodular or spherical iron to high temperatures. The molecules in Ductile Iron have less discontinuities and thus, more ductile. Metal wires can formed with the Ductility of 18 to 30 percent elongation, known as A395. There is no visible elongation in Gray Iron.

  • Tensile Strength

The tensile strength of gry iron is 20,000 pounds per square inch (psi). The least tensile strength of ductile iron is 60,000 psi, whereas the yield strength of ductile iron is 40,000 psi.

  • Impact Resistance

The impact resistance of ductile iron is greater than grey iron. Ductile Iron Casting can withstand up to 7 foot-pounds of impact. Whereas Grey Iron may only withstand up to 2 foot pounds. The nodular or spherical form of graphite in ductile irons is also responsible for this increased resistance.

  • Thermal Conductivity

The thermal conductivity of Grey Iron is 46 Watts per meter, whereas that of Ductile Iron is 36 Watts per meter. The use of Ductile Iron is to make gas cylinders. This is because of its lower thermal conductivity. On the other hand, Grey Iron is used in the making of kitchenware as a result of its greater thermal conductivity.

  • Vibration Damping

The amount of energy that a vibrational wave absorbs depends on how well the two materials match. Gray iron dampens vibrations better than ductile iron. It is because gray iron has non-elastic behavior at very low stresses.

A greater damping capacity improves fatigue resistance. This happens because of the reduced period of time when stress is at or above the fatigue limit. Improvement in fatigue is the most helpful feature of increased damping capacity

The second major advantage is the reduction of vibrations and noise that may be generated by equipment components.


If you are looking for a quality manufacturer to produce your ductile iron casting or grey iron casting, JC Casting is the right one for you! We have a long history of providing high-quality castings. Send us your requirements, you will get an answer within 6 hours. Email: