Alloy steel can be classified in various ways based on the content of alloying elements, main alloying elements, metallographic structure, and usage. Here is a detailed introduction:

Classified by alloy element content. Alloy steel can be divided into low alloy steel (with a total mass fraction of less than 5%), medium alloy steel (with a total mass fraction of 5% to 10%), and high alloy steel (with a total mass fraction of more than 10%).

Classified by major alloying elements. Alloy steel can be named based on the type of alloying element, such as chromium, silicon manganese, etc.

Classified by metallographic organization. Alloy steel can also be classified based on the metallographic structure in the annealed or normalized state, such as pearlite steel, martensitic steel, ferrite steel, austenitic steel, and martensitic steel.

Classified by purpose. Alloy steel is usually divided into three categories based on its use: alloy structural steel, alloy tool steel, and special performance steel.