Casting provides remarkable potential for intricate design details, frequently negating the necessity for supplementary fabrication and assembly. Numerous materials, encompassing various metals and synthetics, lend themselves to casting, with iron and steel standing out for their exceptional mechanical properties suitable across diverse applications.

Despite superficial similarities, cast iron and cast steel exhibit unique characteristics with inherent advantages and disadvantages throughout the manufacturing and application processes. Discerning these distinctions and making informed choices are pivotal, as they can determine the outcome, ensuring robust strength and durability or risking the compromise of parts susceptible to fracture or deformation.

Carbon content is the main difference

Iron and steel, both belonging to the ferrous metals category primarily composed of iron atoms, exhibit a nuanced relationship in the realm of manufacturing. The simplicity ends there, as the production involves a diverse array of alloys and grades. It’s crucial to differentiate between the iron present in everyday items and the scientific element iron (Fe). The elemental form of iron occurs in nature, usually in an oxidized state, necessitating an intricate process called smelting for extraction.

Pure elemental iron, in its natural state, is too soft for practical use in most applications. It gains hardness, and thus utility, through alloying with carbon. The carbon composition becomes the key distinction between cast iron and steel. Cast iron typically contains over 2 percent carbon, while cast steel often comprises between 0.1–0.5 percent carbon.

Castability

Encountering iron or steel in their molten states is a rare experience for most individuals, given their high melting points of approximately 2300˚F for iron and 2600˚F for steel. Moreover, both metals are poured into molds at even hotter temperatures. Those working with liquid iron and steel quickly realize significant differences in pourability and shrinkage rates.

Cast iron, due to its favorable characteristics, is notably easier to cast. It exhibits excellent pourability and experiences less shrinkage compared to steel. This implies that cast iron readily fills intricate voids within a mold and demands less molten material to achieve the desired outcome. These flowability traits make cast iron an ideal choice for architectural and ornate ironwork structures, such as fencing and benches.

Machinability

When it comes to machining, cast iron generally offers greater ease compared to steel. The graphite structure in cast iron facilitates a more straightforward and uniform breaking away during machining. However, the machining process becomes more challenging with harder irons, such as white iron, due to increased brittleness.

In contrast, steel poses challenges in achieving consistent cutting and results in more significant tool wear, leading to elevated production costs. Hardened steels, featuring higher carbon content, contribute to increased tool wear. Yet, softer steel is not necessarily a preferable alternative—low-carbon steels, while softer, can become gummy and pose difficulties during machining processes.