**3. Alloying elements and their effects on steels**

Alloy steel reflects a category of steel facilitated with the addition of different elements. In general, all steels are referred to as alloy steel, while the plain steel is composed of iron added up to 2.06 wt% carbon. However, the term "alloy steel" commonly refers to steels that are alloyed with elements other than carbon. The total wt% of the alloying elements can be up to 20% to provide the material enhanced properties like better wear resistance, strength, or ductility. Low-alloyed steels are distinguished by their lower content of alloys with total content below 5%, whereas in the case of high-alloyed steel, the total sum of elements can be in the range of 5–20%, with improved properties. Apart from the above alloyed steels, there are even unalloyed steels that carry very small quantity of alloys. High-alloyed steel contributes to high strength, toughness, hardness, and creep resistance at specific heat treatment temperature. It also advances machinability and corrosion resistance. In addition, it even strengthens the properties of other alloying elements.
