Four types of carbon steel: advantages and application differences
Carbon steel is one of the most widely used steel categories in the world, with low product cost, high strength, and good processing performance, and is widely used in construction, manufacturing, automobiles, machinery, energy and other industries. Usually we can divide it into four types according to the carbon content: Low Carbon Steel, Medium Carbon Steel, High Carbon Steel and Ultra-High Carbon Steel. Carbon content is a major factor affecting a material's strength, hardness, ductility, and overall properties. This article will provide an in-depth analysis of the four types of carbon steel from the aspects of definition, advantages, performance and common applications.
What is Carbon Steel?
Carbon steel is a type of steel with iron and carbon as the main components, and the carbon content is usually 0.02%–2.0%. Its performance is primarily influenced by carbon content:
The lower the carbon content→ the steel is softer, more ductile, and easier to weld
The higher the carbon content→ the strength and hardness increase, but the toughness decreases and the processing becomes more difficult
As the carbon content increases, the properties of carbon steel gradually change from flexible to high-strength, so it is widely used in a variety of scenarios from thin plates to knives and track steel.
1. Low Carbon Steel
Carbon content: 0.02% – 0.25%
Mild steel, also known as mild steel, is the most used type of carbon steel on the market.
Features & Benefits:
It has excellent ductility and is easy to shape, bend and stamp
Excellent welding performance
Low price and strong economy
Good toughness and not easy to break
Common applications
Building structural parts
Thin steel plate, cold-rolled plate, hot-rolled plate
Steel pipes, welded pipes, black iron pipes
Home appliance shells, automobile exterior panels
nuts, screws and other hardware
Mild steel is mainly used in areas where strength is required but good forming and welding properties are required
2. Medium Carbon Steel
Carbon content: 0.25% – 0.60%
Medium carbon steel has a balance of strength and toughness and can be used in mechanical manufacturing and structural components.
Features & Benefits:
The strength is higher than that of mild steel
Good toughness and wear resistance
It can be further strengthened by heat treatment (quenching, tempering).
The cost is still lower than that of alloy steel
Medium carbon steel, with its higher tensile strength and hardness, is particularly suitable for mechanical structures with heavy loads.
Common applications
Automotive parts (crankshafts, connecting rods, gears)
Mechanical shafts, forgings
Rails, structural steel
Flanges, pressure vessel parts
Medium carbon steel can meet the needs of projects that require high strength but limited cost.
3. High Carbon Steel
Carbon content: 0.60% – 1.00%
High carbon steel is often referred to as "tool steel", which has high hardness and excellent wear resistance.
Features & Benefits:
High hardness and strong wear resistance
High tensile strength
Better performance after heat treatment
It is suitable for heavy-duty and frictional application scenarios
However, high carbon steel has poor welding performance, and the harder the steel, the more brittle it is, so it is mostly used for tools and high-strength mechanical parts.
Common applications
Knives, scissors, cutting tools
High strength spring
Wire rope, steel wire
Dies, stamping tools
High-strength wear-resistant parts
High carbon steel meets the needs of the tool industry that requires high hardness and wear resistance.
4. Ultra-High Carbon Steel
Carbon content: 1.0% – 2.0%
Ultra-high carbon steel is the hardest type of carbon steel and is used to manufacture products that require extremely high strength and wear resistance.
Features & Benefits:
Extremely hard, comparable to some low-alloy tool steels
Extremely resistant to abrasion
Very high strength can be achieved after heat treatment
The disadvantages are:
The molding process is difficult
Extremely poor weldability
Low toughness (brittleness and cracking)
However, its high hardness and strength make it suitable for professional or industrial use.
Common applications
Heavy cutting tools
Industrial knives
Special bearings
Rails (some special models)
Special wear-resistant equipment parts
Ultra-high carbon steel is mostly used in extreme working conditions or industrial manufacturing.
Comparison of the four categories of carbon steel
| Type | Carbon Content | Features | Typical Applications |
|---|---|---|---|
| Low Carbon Steel | 0.02–0.25% | Easy to process, excellent weldability, good toughness | Steel plates, steel pipes, structural components |
| Medium Carbon Steel | 0.25–0.60% | Higher strength, balanced toughness and wear resistance | Automotive parts, shafts, railway tracks |
| High Carbon Steel | 0.60–1.00% | High hardness, strong wear resistance | Cutting tools, springs, industrial tools |
| Ultra-High Carbon Steel | 1.00–2.00% | Extremely high hardness, excellent wear resistance | Special tools, industrial wear-resistant parts |
How to choose the right Carbon Steel?
The choice of carbon steel type should be based on the project needs:
Easy to weld, easy to machine→ mild steel is required
Higher strength and toughness are required for → medium carbon steel
High hardness and wear resistance → high carbon steel is required
Extremely high-strength, industrial tools → ultra-high carbon steel are required
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