Types of Carbon Steel (Low, Medium & High Carbon) – Composition, Properties, and Applications
Steel is the backbone of modern construction, machinery, transportation and manufacturing. It is an alloy of iron and carbon, and the amount of carbon determines the steel’s strength, hardness, ductility, and weldability.
In engineering, carbon steel is mainly classified into:
1️⃣ Low Carbon Steel (Mild Steel)
2️⃣ Medium Carbon Steel
3️⃣ High Carbon Steel
This blog explains each type with Carbon Content, Characteristics, Properties, Weldability, Ductility, Strength, and usage — following general industry definitions used in India.
1️⃣ Low Carbon Steel (Mild Steel)
Carbon Content: 0.05% – 0.25%
✔ Characteristics
- Soft and very ductile
- Easy to cut, bend, form, roll
- Least expensive among all steel categories
✔ Properties
- Good toughness
- Good impact strength
- High machinability
- Suitable for cold-forming and welding
✔ Weldability
⭐⭐⭐⭐⭐ Excellent
Low carbon allows clean, strong weld joints.
✔ Ductility
⭐⭐⭐⭐⭐ Very High
Can bend and elongate without cracking.
✔ Strength
⭐⭐⭐ Low to Medium
Suitable for structures but not for heavy-duty stress parts.
✔ Common Uses
- Structural steel (ISMB, Channels, Angles)
- Steel rods, bars
- Automotive body panels
- Pipes, tubes
- Sheet metal works
- Construction fabrication
2️⃣ Medium Carbon Steel
Carbon Content: 0.25% – 0.60%
✔ Characteristics
- Balanced strength and ductility
- Can be heat-treated (quenching & tempering)
- Stronger than mild steel
✔ Properties
- Good hardness
- Good wear resistance
- Better strength than low carbon steel
✔ Weldability
⭐⭐⭐ Moderate
Requires pre-heating; higher carbon reduces weld quality.
✔ Ductility
⭐⭐⭐ Medium
Not as flexible as mild steel, but not brittle either.
✔ Strength
⭐⭐⭐⭐ High
Suitable for heavy mechanical components.
✔ Common Uses
- Gears, shafts, axles
- Railway parts
- Crankshafts
- Connecting rods
- Industrial machine components
3️⃣ High Carbon Steel
Carbon Content: 0.60% – 1.50%
✔ Characteristics
- Hardest & strongest type of carbon steel
- Brittle in nature
- Excellent wear resistance
✔ Properties
- Very high hardness (especially after heat treatment)
- Highest tensile strength
- Excellent cutting ability
✔ Weldability
⭐⭐ Poor
High carbon causes cracking and difficult fusion.
✔ Ductility
⭐ Low
Prone to fracture when bent.
✔ Strength
⭐⭐⭐⭐⭐ Very High
Ideal for cutting tools and springs.
✔ Common Uses
- Knives, blades, cutting tools
- Chisels, hammers
- Dies and punches
- High-strength wires
- Springs
📊 Comparison Table
| Steel Type | Carbon % | Weldability | Ductility | Strength | Best For |
| Low Carbon | 0.05–0.25% | Excellent | Very High | Low–Medium | Structures, sheets, pipes |
| Medium Carbon | 0.25–0.60% | Moderate | Medium | High | Gears, shafts, machinery |
| High Carbon | 0.60–1.50% | Poor | Low | Very High | Tools, springs, blades |
📝 Conclusion
Carbon content plays the most crucial role in determining steel’s:
Strength
Hardness
Flexibility
Weldability
Mechanical behavior
Low carbon steel is best for construction and fabrication, medium carbon for mechanical parts, and high carbon for tools and springs.
