Steel is an alloy of Iron and the principal (main) alloying element is Carbon. However, there are some exceptions to this definition like interstitial-free (IF) steels and type 409 ferritic stainless steels, in which carbon is considered as an impurity.
When different elements are mixed in smaller quantities in the base element, the resulting product is called an alloy of the base element. Hence steel is an alloy of Iron because Iron is the base element (main constituent) in steel and the principal alloying element is Carbon. Some other elements such as Manganese, Silicon, Nickel, Chromium, Molybdenum, Vanadium, Titanium, Niobium, Aluminum, etc. are also added in varying quantities to produce different grades (or types) of Steel.
Based on the chemical compositions, Steel can be categorized into four (04) basic types:
Carbon steel is the most utilized steel in the industries and accounts for more than 90% of the total steel production. Based on the carbon content, Carbon steels are further classified into three groups.
Carbon content is given in the table below:
| S.No. | Type of carbon steel | Percentage of Carbon |
|---|---|---|
| 1 | Low Carbon Steel/Mild steel | Up to 0.25% |
| 2 | Medium Carbon Steel | 0.25% to 0.80% |
| 3 | High Carbon steel | 0.80% to 2.1% |