In addition to iron and carbon, the main elements of steel include silicon, manganese, sulfur, and phosphorus. There are many different methods for classification of steel. The main methods are as follows:
1, classified by quality
(1) Ordinary steel (P ≤ 0.045%, S ≤ 0.050%)
(2) high quality steel (P, S are ≤ 0.035%)
(3) High-quality steel (P≤0.035%, S≤0.030%)
2, classified by chemical composition
(1) Carbon steel:
a. low carbon steel (C ≤ 0.25%); b. medium carbon steel (C ≤ 0.25 ~ 0.60%); c. high carbon steel (C ≤ 0.60%).
(2) Alloy steel:
a. Low alloy steel (total content of alloying elements ≤ 5%); b. medium alloy steel (total content of alloying elements > 5 to 10%); c. high alloy steel (total content of alloying elements > 10%).
3. Classified according to the forming method:
(1) forged steel; (2) cast steel; (3) hot rolled steel; (4) cold drawn steel.
4. Classification by metallographic organization
(1) Annealed state: a. hypoeutectoid steel (ferrite + pearlite); b. eutectoid steel (pearlite); c. hypereutectoid steel (pearlite + cementite); d. Crust steel (pearlite + cementite).
(2) Normalized state: a. pearlitic steel; b. bainitic steel; c. martensitic steel; d. austenitic steel.
(3) No phase change or partial phase change
5, by purpose
(1) Steel for construction and engineering: a. ordinary carbon structural steel; b. low alloy structural steel; c.
(2) Structural steel
a. Mechanical manufacturing steel: (a) quenched and tempered structural steel; (b) surface hardened structural steel: including carburized steel, ammoniated steel, surface quenching steel; (c) easy-cut structural steel; (d) cold plasticity Steel for forming: steel for cold stamping and steel for cold heading.
b. spring steel
c. bearing steel
(3) Tool steel: a. carbon tool steel; b. alloy tool steel; c. high speed tool steel.
(4) Special performance steel: a. Stainless acid-resistant steel; b. Heat-resistant steel: including anti-oxidation steel, heat-strength steel, gas valve steel; c. electro-thermal alloy steel; d. wear-resistant steel; e. ;f. Electrical steel.
(5) Professional steels – such as steel for bridges, steel for ships, steel for boilers, steel for pressure vessels, steel for agricultural machinery, etc.
6, comprehensive classification
(1) ordinary steel
a. Carbon structural steel: (a) Q195; (b) Q215 (A, B); (c) Q235 (A, B, C); (d) Q255 (A, B); (e) Q275.
b. Low alloy structural steel
c. Ordinary structural steel for specific purposes
(2) high quality steel (including high quality steel)
a. Structural steel: (a) high quality carbon structural steel; (b) alloy structural steel; (c) spring steel; (d) easy-cut steel; (e) bearing steel; (f) high-quality structural steel for specific purposes.
b. Tool steel: (a) carbon tool steel; (b) alloy tool steel; (c) high speed tool steel.
c. Special properties steel: (a) stainless acid-resistant steel; (b) heat-resistant steel; (c) electrothermal alloy steel; (d) electrical steel; (e) high-manganese wear-resistant steel.
7, classified according to smelting methods
(1) According to furnace type
a. Converter steel: (a) acid converter steel; (b) alkaline converter steel. Or (a) bottom-blown converter steel; (b) side-blown converter steel; (c) top-blown converter steel.
b. Electric furnace steel: (a) electric arc furnace steel; (b) electroslag furnace steel; (c) induction furnace steel; (d) vacuum consumable furnace steel; (e) electron beam furnace steel.
(2) According to the degree of deoxidation and the pouring system
a. boiling steel; b. semi-killed steel; c. killed steel; d. special killed steel.