Cast iron and steel are ferrous alloys, both consisting of iron and carbon. Despite this, they are very different in terms of chemical composition and applications.
The physical properties of iron are influenced by the impurities and other elements in it, defining multiple differences between cast iron and steel.
As materials that are widely used in precision mechanical products, knowing their characteristics is crucial to understanding how they are used.
Composition of Cast Iron and Steel
The fundamental difference between cast iron and steel lies in their composition: as mentioned, they are both iron alloys, but have different amounts of carbon and other metals.
It is precisely this discrepancy in concentration that determines the properties of each material. In particular, the percentage of carbon in cast iron is between 2.06% and 6.67%; that of steel between 0.3% and 2.06%.
This value is decisive in defining the type of alloy one is dealing with and determines qualities such as strength, hardness and elasticity. Hence, the variety of application fields in which they are used. Prominent among these is precision mechanics, where they are two of the most widely used metals.
Properties and Characteristics of Steel
Steel is a strong yet very ductile metal that can be bent without breaking. It is characterised by its high tensile strength, which makes it versatile and easy to work with. It is customary to distinguish five basic categories:
- Carbon steel;
- Alloy steel;
- High-strength weakly alloyed steel;
- Stainless steel;
- Tool steel.
Carbon steel is the most common of all and can in turn be subdivided into soft, medium or hard, based on the percentage of carbon it contains. It contains no other elements and is the least valuable of all.
Alloy steel owes its name to the presence of alloying elements, such as nickel, manganese or titanium, which improve its chemical and physical properties.
When a chromium concentration of between 10 and 20 per cent is found in the alloy, we speak of stainless steel, known to be resistant to oxidation and corrosion. There are more than 300 types, but they are mainly divided into Martensitic, Ferritic and Austenitic.
Finally, the last category is tool steel, whose heat resistance is determined by the addition of tungsten, chromium, vanadium and molybdenum.
Properties and Characteristics of Cast Iron
Cast iron has greater resistance to compression and corrosion, being harder, but is inflexible and tensile resistant. It is excellent where lightness is required, as it weighs less than steel. There are four types:
- Grey cast iron;
- White cast iron;
- Spheroidal cast iron;
- Malleable cast iron.
The most widely used is grey cast iron, also known as lamellar cast iron, which due to the presence of lamellae is not very resistant but is able to dampen and absorb mechanical vibrations.
White cast iron differs from the previous one due to the presence of cementite inside it, which gives it a silvery-white appearance and increases its hardness.
From its processing, the other two types are obtained: on the one hand, malleable cast iron, which is easier to work; on the other, spheroidal cast iron, with better mechanical performance.
Applications and Uses
Steel is a very common material, adopted in many different sectors, from the chemical industry to transport and more everyday uses such as household appliances and packaging.
Due to its characteristics, the field of application of cast iron is very varied and encompasses several areas. These include the automotive, textile and glass industries, but not only: it is also widely used for machine tools and in hydraulics.
It is not uncommon for cast iron and steel to have common uses, as is the case in precision mechanics, for example, which makes extensive use of these materials. For the construction of test benches, in fact, Bonanomi offers bases and structures in both cast iron and electro-welded steel.