Steel can be divided into low carbon steel, medium carbon steel, high carbon steel, alloy steel and stainless steel and other categories.

1. Low carbon steel: carbon content below 0.05%. Low strength, good plasticity, good welding performance, easy processing, widely used in some light load structure.

2. Medium carbon steel: carbon content between 0.15% and 0.45%. High strength and toughness, can be applied to some mechanical parts that require higher strength.

3. High carbon steel: the carbon content is more than 0.45%. The strength and hardness are very high, but the plasticity is poor, mainly used in the manufacture of tools, springs and other high strength and high hardness parts.

4. Alloy steel: in addition to carbon, it also contains other alloying elements (such as silicon, manganese, chromium, nickel, molybdenum, etc.). It has high strength, high toughness, high temperature strength, corrosion resistance and good mechanical processing performance.

5. Stainless steel: the main components are iron, chromium, nickel, etc. It has the advantages of good corrosion resistance, high strength, good processing performance, easy maintenance and so on. It is widely used in kitchen utensils, building decoration, chemical industry and other fields.

In addition to the above classification, steel can also be divided into structural steel, tool steel, heat-resistant steel and so on according to different uses. Thus, steel is a very broad material with many different species, properties, and uses.