Alloy steel is a type of steel that has presence of certain other elements apart from iron and carbon. Commonly added elements in alloy steel are manganese, silicon, boron, chromium, vanadium and nickel. Carbon steel is also known as plain steel and is an alloy of steel where carbon is the main constituent and no minimum percentage of other alloying elements is mentioned. Carbon steel is not stainless steel as it is classified under alloy steels.