Carbon steel is an iron-carbon alloy with a carbon content between 0.0218% and 2.11%. It has become one of the most widely used metal materials in modern industry due to its low production cost and strong performance adaptability. The following is a detailed introduction from the aspects of composition, classification, performance characteristics, and application fields:

1. Core components of carbon steel

The main components of carbon steel are iron (Fe) and carbon (C). In addition, it may contain a small amount of manganese (Mn, usually ≤1.2%), silicon (Si, usually ≤0.4%), and trace amounts of sulfur (S), phosphorus (P) and other impurities. Among them:

Carbon content is the key factor that determines the performance of carbon steel, and directly affects its mechanical properties such as strength, hardness, and toughness.

Sulfur and phosphorus are harmful impurities: sulfur will cause carbon steel to be "hot brittle" (easy to break during high-temperature processing), and phosphorus will cause "cold brittle" (toughness drops sharply at low temperatures), so the content of the two must be strictly controlled in industrial production.

2. Classification of carbon steel

The classification of carbon steel is based on various criteria, and the following are the most common ones:

Classification by carbon content

Low carbon steel: carbon content ≤0.25%, such as Q235 steel. It is characterized by good toughness, plasticity, excellent welding performance, easy processing, but low strength, and is often used to manufacture steel plates, steel pipes, rivets, etc.

Medium carbon steel: carbon content 0.25%~0.60%, such as 45 steel. It has high strength and hardness, moderate toughness, and can be further improved through heat treatment (such as quenching and tempering). It is mostly used to manufacture mechanical parts such as shafts, gears, and connecting rods.

High carbon steel: carbon content 0.60%~2.11%, such as T10 steel. It has high hardness and good wear resistance, but poor toughness. It is mainly used to manufacture tools, molds, springs, etc.

Classification by quality grade (based on sulfur and phosphorus content)

Ordinary quality carbon steel: sulfur content ≤0.050%, phosphorus content ≤0.045%, suitable for occasions with low performance requirements, such as steel bars for construction.

High-quality carbon steel: sulfur and phosphorus content are both ≤0.035%, mechanical properties are more stable, and are often used for structural parts in machinery manufacturing.

Advanced high-quality carbon steel: sulfur content ≤0.025%, phosphorus content ≤0.030%, and "A" is added after the steel number (such as 45A), suitable for precision parts with higher requirements.

Classification by use

Carbon structural steel: mainly used for engineering structures such as buildings, bridges, and ships, emphasizing the balance of strength and toughness, such as Q345 steel.

Carbon tool steel: used to manufacture knives, measuring tools, molds, etc., focusing on hardness and wear resistance, such as T8 steel ("T" represents tool steel).

3. Performance characteristics of carbon steel

Mechanical properties: As the carbon content increases, the strength and hardness gradually increase, but the plasticity, toughness and welding performance decrease. For example, low carbon steel can be easily bent and formed, while high carbon steel is more brittle and is prone to breakage under excessive force.

Processing performance: low carbon steel is easy to cut and weld; medium carbon steel requires appropriate adjustment of processing parameters; high carbon steel is more difficult to process and usually requires pre-heat treatment to soften.

Cost advantage: Compared with stainless steel, alloy steel, etc., carbon steel has a simple production process and low raw material cost, which is suitable for large-scale application.

4. Typical application scenarios

Construction field: steel bars made of low carbon steel are used for concrete structure reinforcement, and steel plates are used for building frames.

Machinery manufacturing: gears and shaft parts made of medium carbon steel are responsible for transmitting power and torque.

Tool manufacturing: files and drill bits made of high carbon steel take advantage of their high hardness and wear resistance.

Daily life: iron pots and farm tools made of carbon steel are cost-effective.