Low Carbon Steel, commonly known as Mild Steel, is the most widely used category of carbon steel due to its excellent formability, weldability, machinability, and cost-effectiveness. With a carbon content typically between 0.05% and 0.25%, mild steel exhibits a soft, ductile structure that is easy to process and fabricate.
Because of its balanced mechanical properties and ease of manufacturing, low carbon steel is the backbone material for construction, infrastructure, automotive, pipelines, fabrication, and general engineering applications worldwide.
Typical Chemical Composition
| Element | Typical Range (%) |
|---|---|
| Carbon (C) | 0.05 – 0.25 |
| Manganese (Mn) | 0.25 – 1.00 |
| Silicon (Si) | ≤ 0.40 |
| Sulphur (S) | ≤ 0.050 |
| Phosphorus (P) | ≤ 0.050 |
| Iron (Fe) | Balance |
Microstructure & Metallurgy
Low carbon steel primarily consists of ferrite with small amounts of pearlite.
• Ferrite provides softness, ductility, and excellent formability
• Pearlite contributes modest strength and hardness
This simple microstructure makes mild steel easy to weld, resistant to brittle fracture, and stable during forming and fabrication.
Key Characteristics
High Ductility & Formability
• Easily bent, rolled, stamped, deep-drawn, and pressed
• Suitable for hot and cold forming processes
Excellent Weldability
• Low carbon minimizes hard martensite formation in HAZ
• Compatible with MIG, TIG, Arc, and resistance welding
• Usually no preheating or post-weld heat treatment required
Good Strength-to-Cost Ratio
• Adequate structural strength at low cost
• Ideal for large-volume and mass-production use
High Machinability
• Easy machining with conventional tools
• Clean cuts with minimal tool wear
Typical Mechanical Properties
| Property | Typical Range |
|---|---|
| Tensile Strength | 350 – 450 MPa |
| Yield Strength | 180 – 280 MPa |
| Elongation | 20 – 35% |
| Hardness | 90 – 130 HB |
| Impact Toughness | High |
| Density | ~7.85 g/cm³ |
| Modulus of Elasticity | ~200 GPa |
Refining & Manufacturing Properties
Low carbon steel is commonly produced using:
• Basic Oxygen Furnace (BOF) – large-scale production
• Electric Arc Furnace (EAF) – often using recycled steel
These processes allow precise control of carbon content, reduction of sulphur and phosphorus, and improved steel cleanliness.
Heat Treatment Compatibility
Although mild steel cannot be significantly hardened by heat treatment alone, it responds well to:
• Annealing – improves ductility and machinability
• Normalizing – improves grain uniformity and strength
• Case hardening (carburizing) – increases surface hardness while retaining a tough core
Corrosion Behavior
Mild steel has limited inherent corrosion resistance and typically requires protection such as:
• Galvanizing (zinc coating)
• Painting or powder coating
• Oil or chemical coatings
Available Forms
✔ Sheets & plates (hot rolled / cold rolled)
✔ Coils
✔ Pipes & tubes (ERW / seamless)
✔ Structural sections (beams, channels, angles)
✔ Bars (round, square, flat)
✔ Wire rods & wires
✔ TMT & reinforcement bars
Applications
Construction: Buildings, bridges, structural frameworks
Automotive: Chassis, body panels, brackets
Manufacturing: Machinery frames, tanks, enclosures
Pipelines: Water, gas, and utility pipelines
General Engineering: Furniture, fasteners, hardware
Advantages
✔ Easy fabrication and processing
✔ Excellent weldability
✔ Cost-effective and widely available
✔ Good impact resistance
✔ Compatible with coatings and surface treatments
Limitations
⚠ Cannot be hardened through heat treatment alone
⚠ Lower strength than medium and high carbon steels
⚠ Requires corrosion protection
Why Choose Low Carbon Steel
Low carbon steel remains the preferred material for mass-scale industrial use due to its versatility, ease of fabrication, structural reliability, and affordability. Its adaptability across manufacturing processes makes it indispensable in modern engineering and construction.