Comparing Cast Iron Tensile Strengths

The tensile strength of different types of cast iron varies significantly based on their microstructure, particularly the form of carbon present.

Key Cast Iron Types & Strength

• White Cast Iron: Contains carbon as iron carbide (cementite), making it very hard and brittle with low tensile strength.
• Grey Cast Iron: Features graphite in flake form. This structure causes stress concentrations, reducing its overall tensile strength compared to other types. Typical tensile strength ranges from 200-400 MPa.
• Pig Iron: This is the intermediate product of smelting iron ore in a blast furnace. It has a very high carbon content (3.5-4.5%) and other impurities, making it brittle and generally unsuitable for applications requiring high tensile strength without further processing.
• Nodular Cast Iron (Ductile Iron): Graphite is present in spherical nodules (spheroids) rather than flakes. This nodular shape minimizes stress concentration, significantly increasing both tensile strength and ductility. Typical tensile strength ranges from 400-700 MPa, and can be higher in specific grades.

Conclusion on Tensile Strength

Due to its graphite nodule structure, Nodular cast iron exhibits the highest tensile strength among the listed types of cast iron, offering superior mechanical properties for demanding applications.