What Is The Difference between Iron And Steel?

In daily life, we often confuse steel and iron as a concept and regard them as the same product. In fact, steel and iron are different products. So, what is the difference between iron and steel?

Steel is a general term for iron-carbon alloys with a carbon content of 0.02% to 2.11% by mass. 

The chemical composition of steel can vary greatly. In actual production, different alloying elements are often added to steel according to different uses, such as silicon, manganese, nickel, vanadium, etc.

Generally, iron with a carbon content of less than 0.0218% is called wrought iron or pure iron, iron with a content of 0.0218-2.11% is called steel, and iron with a content of 2.11-6.69% is called cast iron (or pig iron). 

Wrought iron is soft and has good plasticity, it is easy to deform and has low strength and hardness, and is not widely used; pig iron contains a lot of carbon, it is hard and brittle, and has almost no plasticity. 

Steel not only has good plasticity, but also has excellent physical and chemical application properties such as high strength, good toughness, high temperature resistance, corrosion resistance, easy processing, impact resistance, and easy refining, so it is widely used.

Iron-carbon alloys can be divided into the following three categories according to carbon content:

① Industrial pure iron (or wrought iron): w(C) < 0.0218%

② Steel: w(C) = 0.0218% ~ 2.11%

③ Cast iron (or pig iron): w(C) = 2.11% ~ 6.69%

The mainly difference between iron and steel is as below:

1. Strength and Weight

The strength of steel and iron is unmatched. It is stronger than iron and has a higher density. Due to this strength and versatility, steel is extremely popular in construction projects. In the mid-19th century, steel was mass-produced and replaced iron as the primary material for construction.

Steel is extremely useful in projects such as buildings, houses, and rail lines due to its incredible strength. This type of engineering requires the plasticity that steel provides. Steel is also lighter than iron and has a higher ability to withstand tensile stress. The strength and weight of steel means that it is unlikely to warp, deform, or bend.

Cast iron is known for its strength rather than its ductility. This means that cast iron can be more brittle and not as useful in construction. Therefore, iron is more commonly used to make tools.

2. Durability

When looking to build a structure that will hold up to time and the elements, steel is the best choice. Structural steel can withstand extreme forces and heat. This means that it can withstand fire and has a high resistance to other elements such as wind and rain. Steel has a lower risk of being affected by mold or mildew than iron. This can ultimately affect the integrity of a building or construction project.

Because of steel's uses, it is considered one of the most durable materials in construction. Steel will not crack, warp, twist, split or rot. Iron cannot compare to these qualities. Steel's durability is one of the main reasons why it is preferred over iron in construction projects. Steel is also well suited to making sections, such as I-beams and simple cross-sections.

3. Corrosion Resistance

Corrosion is a natural process that changes the composition of a metal through chemical oxidation. Oxidation causes the metal to rust and turn orange. Steel is considered more corrosion resistant than iron.

Iron oxidizes easily and therefore rusts. While water may affect the integrity of steel, there are steps that can be taken to reduce this risk and increase resistance. Steel can be treated with surface treatments such as protective coatings and sprays. It can also be coated with refractory materials to prevent corrosion. Steel is also a non-porous alloy, which means it has a natural resistance to corrosion.