In addition to iron and carbon, the main elements of steel include silicon, manganese, sulfur, and phosphorus.
There are various classification methods for steel, and 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. low-temperature steel ;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