Steel is an iron carbon alloy with 0.04%-2.3% carbon content, it is called steel and iron with iron as we all know.

Typically the carbon content is less than 1.7% in order to ensure its plasticity, in addition to the primary elements like iron, carbon,it also contains manganese , silicon, phosphorus, sulfur, etc. On the basis of different ingredients, it can be divided into carbon steel and alloy steel. And also can be divided into structural steel, tool steel and special steel with its different  performance and use.

1.To perform the Quality rating
(1) The general steel (P:less than or equal to 0.045%, S:less than or equal to 0.050%)
(2) The high quality steel (P, S is less than or equal to 0.035%)
(3) The high-grade steel (P: less than or equal to 0.035%, S:less than or equal to 0.030%)
2. According to the classification of chemical composition
(1) Carbon steel: low carbon steel (C:less than or equal to 0.25%), medium carbon steel (C :less than or equal to 0.25~0.60%) ,high carbon steel (C:less than or equal to 0.60%).
(2) Alloy steel:low alloy steel (alloy elements is less than or equal to 5%), medium alloy steel (alloy elements is higher than or equal to 5~10%) ,high alloy steel (alloy elements is higher than or equal to 10%).
3. To perform the forming method
Forging steel, cast steel, hot rolled steel, cold rolled steel.
4.Classify by applications
(1)Construction and engineering: general carbon structural steel, low alloy structural steel, concrete iron steel
(2)Structural steel: quenched and tempered steel, surface hardening structural steel, free cutting structural steel, cold plastic forming steel
(3)Tool steel: carbon tool steel, alloy tool steel, high speed tool steel
(4)Special use steel: stainless steel heat resistant steel, stainless acid-resisting steel, electrical thermal alloy steel, abrasion resistant steel plate, low temperature steel, electrical steel
(5)Professional use steel: bridge steel plate, ship steel plate, boiler steel, pressure vessel steel, machinery steel.