Steel, an alloy of iron and other elements, principally carbon, is by far the most widely used and important metal in the world. It is used to make a vast range of products and constructions, from large ships and bridges to smaller items such as paperclips and cutlery. Although steel has been around for thousands of years, it is constantly undergoing changes and improvements.
Steel is made from iron ore, steel scrap, coal and limestone, which are heated in a furnace and combined with oxygen. The oxygen combines with the impurities in the iron ore, separating some oxygen from the iron and creating steel as a result. A wide range of elements, such as manganese, chromium and nickel, can be added to the molten steel in order to alter its properties, such as its strength, toughness, ductility and hardness.
Steel is classified according to its composition, structure and properties. There are a number of common grades, including carbon steel, alloy steel, high-strength low-alloy steel and stainless steel. Carbon steel contains up to 2 percent carbon and is the most popular grade because it is relatively inexpensive and has a wide range of applications. Alloy steel contains other alloying elements, including manganese, chromium and nickel. High-strength low-alloy steel has a higher strength-to-weight ratio than other grades, and is often used in the manufacture of large structures, such as bridges. Stainless steel is an alloy of iron and at least 10.5 percent chromium and is used in a wide range of applications, particularly where resistance to corrosion is important.
Steel is also classified according to its structure which may be either hot-rolled or cold-rolled. Hot-rolled steel is made by heating the steel in a rolling mill and then cooling. This process results in the steel being softer and less resistant to corrosion. It is typically used in the production of structural components, such as beams and columns. Cold-rolled steel is processed in a similar way to hot-rolled steel but is cooled much further. This results in a far harder steel which is ideal for applications where strength is more important than ductility.
Steel is an incredibly versatile material, allowing for the production of a wide range of products with varying properties suitable for different applications. It is also a very durable material, making it ideal for many uses. Steel is an incredibly important component of modern society and its importance is only set to increase in the coming years.
