Carbon steel is the earliest used and most used basic material in modern industry. The steel with a carbon content of less than 2.11% without specially added alloying elements is called carbon steel, or carbon steel.

Structure classification

(1) According to smelting method and equipment:
a. Open hearth steel b. Converter steel c. Electric furnace steel

(2) According to the degree of deoxidizer and deoxidation during smelting and pouring:
a. Boiling steel: At the end of smelting and before pouring, ferromanganese and a small amount of aluminum are used as deoxidizers for slight deoxidation, so that a large amount of oxygen remains in the molten steel; after pouring into the ingot mold, the oxygen in the steel reacts with carbon to produce A large number of CO bubbles cause the surface of the molten steel to boil violently, so it is called boiling steel.
b. Killed steel: Before the molten steel is poured, deoxidizers such as ferromanganese, ferrosilicon and aluminum are used to fully deoxidize, so that no CO bubbles are generated when the molten steel is poured into the ingot mold and solidifies, and the molten steel in the ingot mold is calm, so it is called Killed steel.
c. Continuous casting billet: The steel billet produced directly by the molten steel through the continuous casting machine is called continuous casting billet.
d. Semi-killed steel: The degree of deoxidation of molten steel is not sufficient. It is between rimmed steel and killed steel, and slightly boils during pouring. The structure and properties of steel are also between that of killed steel and rimmed steel.

(3) Classified by carbon content
a. Low carbon steel: the carbon content of steel wc<0.25%.
b. Medium carbon steel: The carbon content of steel is between 0.25% and 0.60% (wc=0.25% to 0.60%).
c. High carbon steel: the carbon content of steel wc>0.60%.

(4) According to the quality of carbon steel
This classification method is mainly classified according to the mass fraction of harmful impurities S and P contained in carbon steel.
a. Ordinary carbon steel: ws≤0.050%, wp≤0.045%.
b. High-quality carbon steel: ws≤0.035%, wp≤0.035%.
c. High quality carbon steel: ws≤0.025%, wp≤0.025%.
d. Special high-quality carbon steel: ws≤0.015%, wp≤0.025%.

(5) Classified according to the purpose of steel
a. Carbon structural steel: Mainly used in the manufacture of various mechanical parts and engineering structural parts, and its carbon content is generally less than 0.70%, which belongs to the series of low carbon steel and medium carbon steel.

b. Carbon tool steel: mainly used to manufacture various cutting tools, measuring tools, and molds. Its carbon content is generally greater than 0.70%, which belongs to the category of high carbon steel.