Most people know the two main ingredients of steel – iron and carbon. These are the two ingredients that MUST be present for a material to be considered steel, but the steel we use today is often more complex than that.
The World Steel Association believes there to be over 3,500 different grades of steel being used today, and each one has a different chemical makeup. Steel generally contains a carbon content between 0.002% and 2.1%, and the precise carbon content along with that of other alloying metals can make a big difference in the resulting properties of the metal.
Carbon Steels are by far the most common, and are used for a wide range of applications – particularly in construction. They make up about 90% of steels being produced today, and can contain up to 2.1% carbon (although rarely more than 1%). The lower the carbon content, the more workable the steel is. As the carbon content rises, the steel becomes stronger but also becomes more difficult to form, more difficult to weld and also lowers the melting point.
Alloy steels use a range of different elements to change the properties of the metal. Using elements such as manganese, silicon, nickel, titanium, chromium, copper and aluminium to affect the steel’s hardness, strength, corrosion resistance, weldability, formability and ductility. These steels are normally used for automotive construction, power generation, electric motors and more.
Stainless steels contain around 10-20% chromium, which drastically increases the corrosion resistance. Stainless steels are broken up into three main groups – austenitic, ferritic and martensitic. Austenitic steels contain around 8% nickel, are non-magnetic, heat-treatable and are often used in food production applications. Ferritic steels contain elements such as molybdenum, titanium and aluminium. They can’t be heat-treated, but can be strengthened through cold-working processes. Martensitic steels have a relatively high carbon content of around 1.2%, which makes them suitable for use in knives, cutting tools and surgical equipment.
Tools steels are developed for high durability, heat resistance and durability – which make them perfect for cutting, drilling and other hard wearing applications. They generally contain elements such as vanadium, chromium, molybdenum, and tungsten in varying quantities.
Of course, these are just some of the common types of steel used today, but there are thousands out there, and as the needs of consumers change, new types of steel are developed. Steel is an exceptionally versatile material with seemingly endless uses and capabilities.