Alloy steels are alloys of iron and carbon with other alloying elements added deliberately in order to improve their physical, chemical, mechanical and technological properties. Commonly used alloying elements are: molybdenum, vanadium, aluminium, tungsten, nickel, chromium, manganese, silicon, titanium, niobium and cobalt. Depending on the application, the percentage of those elements may vary from 0.01% up to tens percents.
Because of cumulative fraction of alloying elements, alloy steels may be broken down into three groups:
- low-alloy steels (content of one elements [except for carbon] is not greater that 2.0% and the total content of all additional elements is not greater that 3.5%),
- medium-alloy steels (content of one elements [except for carbon] is greater than 2.0% but less than 8.0% and the total content of all additional elements is not greater that 12%),
- high-alloy steels (content of one elements [except for carbon] is greater than 8.0% and the total content of all additional elements is not greater that 55%).