Steel is an iron carbon alloy with a carbon content ranging from 0.04% to 2.3%. In order to ensure its toughness and plasticity, the carbon content generally does not exceed 1.7%. The main elements of steel include silicon, manganese, sulfur, phosphorus, etc. in addition to iron and carbon. There are various classification methods for steel, with the following eight main methods:

1. Classified by quality

(1) Ordinary steel (P ≤ 0.045%, S ≤ 0.050%)

(2) High quality steel (both P and S ≤ 0.035%)

(3) High quality steel (P ＜ 0.035%, S ≤ 0.030%)

2. Classification by chemical composition

1) Carbon steel: a. Low carbon steel (C ≤ 0.25%); b. Medium carbon steel (0.25 ＜ C ≤ 0.60%); c. High carbon steel (C>0.60%).

2) Alloy steel: a. Low alloy steel (total alloy element content ≤ 5%) b. Medium alloy steel (total alloy element content 5-10%) c. High alloy steel (total alloy element content>10%).

3. Classification by forming method: (1) forged steel; (2) Cast steel; (3) Hot rolled steel; (4) Cold drawn steel.

4. Classification by metallographic structure (a scientific study of the internal microstructure of steel)

1) Annealed a. hypoeutectoid steel (ferrite+pearlite) b. eutectoid steel (pearlite) c. hypereutectoid steel (pearlite+cementite) d. ledeburite steel (pearlite+cementite).

2) Normalized state: a. Pearlitic steel; b. Bainitic steel; c. Martensitic steel; d. Austenitic steel.

3) Without or partially undergoing phase transition

5. Classification by purpose

1) Steel for construction and engineering purposes: a. Ordinary carbon structural steel; b. Low alloy structural steel; c. Steel reinforcement.

2) Structural steel: a. Steel for mechanical manufacturing: (a) Quenched and tempered structural steel; (b) Surface hardened structural steel: including carburized steel, ammonia steel, and surface quenched steel; (c) Easy to cut structural steel; (d) Cold plastic forming steel: including cold stamping steel and cold heading steel. 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 and acid resistant steel; b. Heat resistant steel includes oxidation resistant steel, heat resistant steel, and gas valve steel; c. Electric heating alloy steel; d. Wear resistant steel; e. Low temperature steel; f. Electrical steel

5) Professional steel - such as steel for bridges, ships, boilers, pressure vessels, 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-grade high-quality steel)

a. Structural steel: (a) High quality carbon structural steel; (b) Alloy structural steel; (c) Spring steel; (d) Easy cutting 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 performance steel: (a) stainless and acid resistant steel; (b) Heat resistant steel; (c) Electric heating alloy steel; (d) Electrical steel; (e) High manganese wear-resistant steel.

7. Classification by smelting method

1) Classified by furnace type

a. Open hearth steel (using air as oxidant): (a) acidic open hearth steel; (b) Alkaline open-hearth steel.

b. Converter steel (using oxygen as oxidant): (a) acidic converter steel; (b) Alkaline converter steel. Or (a) bottom blown converter steel; (b) Side blown converter steel; (c) Top blown converter steel.

c. Electric furnace steel (refining high-quality 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 pouring system, a. boiling steel (incomplete deoxidation degree); b. Semi killed steel (with a degree of deoxygenation between boiling steel and killed steel); c. Killed steel (with a relatively complete degree of deoxidation); d. Special killed steel (with the most complete degree of deoxidation and high quality steel).

8. Classified by appearance: divided into four categories: a. profiles, b. plates, c. pipes, and d. metal products.

a. Profile:

Heavy rail: Steel rails weighing more than 30 kilograms per meter (including crane rails); Light rail: A steel rail with a weight of less than or equal to 30 kilograms per meter. Large, medium, and small section steels: ordinary round steel, square steel, flat steel, hexagonal steel, I-beam, channel steel, equal and unequal angle steel, and threaded steel, etc. Wire: Round steel and wire rods with a diameter of 5-10 millimeters. Cold formed steel: A type of steel formed by cold bending steel or steel strip. High quality profiles: High quality round steel, square steel, flat steel, hexagonal steel, etc.

b. Plate;

Thin steel plate: Steel plate with a thickness of 4 millimeters or less. Medium and thick steel plates: Steel plates with a thickness greater than 4 millimeters. Middle plate: thickness greater than 4mm but less than 20mm); Thick plate: thickness greater than 20mm but less than 60mm; Extra thick plate: thickness greater than 60mm. Steel strip: also known as strip steel, it is actually a thin steel plate that is long and narrow and supplied in coils. Electrical silicon steel sheet: also known as silicon steel sheet or silicon steel sheet.

c. Pipe material:

Seamless steel pipe: a seamless steel pipe produced by methods such as hot pressing, cold rolling (cold drawing or extrusion), etc. Welded steel pipe: a steel pipe made by bending a steel plate or strip into shape and then welding it.

d. Metal products: including steel wire, wire rope, steel strand, etc.