What is steel?

Here is the definition:

Steel is an iron-carbon alloy with a carbon content of 0.04%-2.3%.

In order to ensure its toughness and plasticity, the carbon content of steel is generally not more than 1.7%.

The main elements of steel are iron and carbon, as well as silicon, manganese, sulfur and phosphorus.

The classification methods of steel are varied, and the main methods are as follows:

Steel Classification

Classification by quality. 

  • Ordinary steel（P≤0.045%，S≤0.050%） 
  • High-quality steel（P、S≤0.035%） 
  • Advanced high-quality steel（P≤0.035%，S≤0.030%） 

Classification by chemical composition.

(1) Carbon steel

  • Low carbon steel（C≤0.25%）
  • Medium carbon steel（C≤0.25~0.60%）
  • High carbon steel（C≤0.60%）

(2) Alloy steel

  • Low alloy steel（Total amount of alloying element≤5%）
  • Medium alloy steel（Total amount of alloying element＞5~10%）
  • High alloy steel（Total amount of alloying element.＞10%）

Classification by forming method.

  • Forged steel
  • Cast steel
  • Hot rolled steel
  • Cold drawn steel

Classification by metallographic structure.

(1) Annealed

  • Hyposteel（ferrite +pearlite）
  • Eutectoid steel（pearlite）
  • Hypereutectoid steel（pearlite +cementite）
  • Ledeburitic steel（pearlite +cementite）

(2) Normalized

  • Pearlitic steel
  • Bainite steel
  • Martensitic steel
  • Austenitic steel 

(3) Without phase change or partial phase change.

Classification by use.

(1) Construction and engineering steel

  • Ordinary carbon structural steel
  • Low alloy structural steel.
  • Reinforced steel

(2) Structural steel

a. Mechanical manufacturing steel

  • Tempered structural steel
  • Surface hardening structural steel: including carburized steel, carburized steel, surface hardening steel
  • Free-cutting structural steel
  • Cold plastic forming steel: Including cold stamping steel, cold heading steel.

b. Spring steel

c. Bearing steel

(3) Tool steel

  • Carbon tool steel.
  • Alloy tool steel
  • High-speed tool steel

(4) Special performance steel

  • Stainless acid-resisting steel
  • Heat resistant steel: including anti-oxidation steel, refractory steel, air valve steel;
  • Electrothermal alloy steel.
  • Wear-resistant steel
  • Cryogenic steel
  • Electrical steel

(5) Steel for dedicated use

Such as steel for bridge, ship, boiler, pressure vessel, agricultural machinery, etc.

Comprehensive classification

(1) Ordinary steel

a. Carbon structural steel.

  • Q195
  • Q215(A、B)
  • Q235(A、B、C)
  • Q255(A、B)
  • Q275

b. Low alloy structural steel. 

c. General structural steel for a specific purpose.

(2) Quality steel (including high-grade steel)

a. Structural steel

  • Quality carbon structural steel
  • Alloy structural steel
  • Spring steel
  • Free-cutting steel
  • Bearing steel
  • High-quality structural steel for a specific purpose.

b. Tool steel

  • Carbon tool steel.
  • Alloy tool steel
  • High-speed tool steel

c. Special performance steel

  • Stainless acid-resisting steel.
  • Heat resistant steel
  • Electrothermal alloy steel.
  • Electrical steel
  • High manganese steel

Classification by smelting method.

(1) Classification by the furnace types

a. Open-hearth steel

  • Acid open-hearth steel
  • Basic open-hearth steel

b. Converter steel

  • Acid bessemer steel
  • Basic bessemer steel

OR

  • Bottom blown converter steel
  • Side-blown converter steel
  • Top blown converter steel

c. Arc-furnace steel

  • Electric-art furnace steel
  • Electroslag furnace steel
  • Induction furnace steel
  • Vacuum self-consuming furnace steel
  • Electron beam furnace steel

(2) Classification by the degree of deoxidation and the teeming system.

  • Rimming steel
  • Semi killed steel
  • Killed steel
  • Special killed steel