While cast iron has several desirable properties, it also has some disadvantages when compared to steel as a structural material. Here are a few disadvantages of using cast iron:
Brittle nature: Cast iron is more brittle than steel. It has low tensile strength and low ductility, which means it is more prone to cracking or breaking under tensile or impact loads. Steel, on the other hand, has higher tensile strength and greater ductility, making it less likely to fail catastrophically.
Weight: Cast iron is denser and heavier than steel. This can be a disadvantage when weight reduction is a critical factor in the design of a structure. Steel offers a higher strength-to-weight ratio, allowing for lighter structures without compromising strength.
Limited malleability: Cast iron is less malleable than steel, which means it is less easily shaped or formed. Steel, due to its higher ductility, can be easily shaped into various structural forms, allowing for more versatility in design and construction.
Corrosion susceptibility: Cast iron is more susceptible to corrosion compared to many types of steel. It is prone to rusting when exposed to moisture and air, which can weaken the material over time. Steel can be protected from corrosion through various methods such as coating, galvanizing, or alloying.
Weldability: Cast iron has limited weldability compared to steel. It is more challenging to weld due to its higher carbon content, which can lead to cracking during the welding process. Steel, especially mild or low carbon steel, is more weldable and can be easily joined using various welding techniques.
Inconsistent properties: The properties of cast iron can vary across different sections or parts of a casting. It is susceptible to internal defects such as voids, inclusions, or uneven cooling, which can lead to inconsistencies in mechanical properties. Steel, especially when produced through controlled manufacturing processes, offers more consistent and predictable properties.
These disadvantages of cast iron compared to steel make steel a more preferred choice for many structural applications where strength, ductility, weight, and ease of fabrication are critical factors. However, cast iron still has its own niche uses, such as in certain architectural applications or for its unique aesthetic qualities.