Carbon Steel (Fe+C)
Carbon steel is the most widely used engineering material, comprising iron with 0.05–2.0% carbon content. It offers an excellent balance of strength, formability, and cost-effectiveness, making it the backbone of construction, infrastructure, and manufacturing industries worldwide.
Properties
- Density
- 7,850 kg/m³
- Melting Point
- 1,425–1,540 °C
- Boiling Point
- 2,862 °C
- Thermal Conductivity
- 45–54 W/(m·K)
- Electrical Resistivity
- 1.43 × 10⁻⁷ Ω·m
- Tensile Strength
- 370–700 MPa
- Yield Strength
- 235–460 MPa
- Hardness
- 120–300 HB
- Elongation
- 15–25%
- Crystal Structure
- BCC (Ferrite) / FCC (Austenite)
Common Grades
- S235JR: General structural steel, min yield 235 MPa. Widely used in buildings and bridges.
- S275JR: Medium-strength structural steel, min yield 275 MPa. Common in general construction.
- S355J2: High-strength structural steel, min yield 355 MPa. Used in heavy-load structures.
- C45: Medium carbon steel (0.45% C). Used for shafts, gears, and machine parts.
- S460: High-strength low-alloy steel. Used in bridges and high-rise buildings.
- S690Q: Ultra-high-strength quenched and tempered steel, min yield 690 MPa. Mobile cranes, mining equipment.
- Corten A (S355J0WP): Weathering steel — forms protective rust patina, eliminating need for painting. Bridges, facades, sculpture.
Applications
- Construction: Structural beams (IPE/HEA), columns, reinforcement bars, bridges, platforms
- Automotive: Chassis components, body panels, drivetrain parts, suspension systems
- Shipbuilding: Hull plating, deck structures, bulkheads, keel sections
- Energy: Pipelines, pressure vessels, wind turbine towers, storage tanks
- Manufacturing: Machine frames, conveyor systems, tooling fixtures, structural fabrication
FAQ
What is the difference between mild steel and carbon steel?
Mild steel is a subset of carbon steel with low carbon content (0.05–0.25% C). All mild steel is carbon steel, but carbon steel also includes medium (0.25–0.60% C) and high carbon (0.60–2.0% C) varieties with different mechanical properties.
What is the most common carbon steel grade for construction?
S355J2 is the most widely used structural carbon steel grade in European construction due to its excellent strength-to-weight ratio, good weldability, and compliance with Eurocode 3 for structural design.
Can carbon steel be used outdoors without coating?
No, carbon steel has poor corrosion resistance and will rust rapidly when exposed to moisture. Outdoor applications require protective coatings such as hot-dip galvanizing (ISO 1461), paint systems, or weathering steel grades like Corten.
What welding process is best for carbon steel?
MIG/MAG welding (GMAW) with CO₂/Argon shielding gas is the most productive process for carbon steel. For thinner sections, TIG welding provides higher quality. MMA (stick) welding is preferred for site work and all-position welding.
What is weathering steel (Corten)?
Weathering steel contains small amounts of copper, chromium, and phosphorus that cause it to form a stable, protective rust patina when exposed to the atmosphere. This eliminates the need for painting and provides 50+ years of maintenance-free service. Common grades are Corten A (S355J0WP) and Corten B (S355J2WP).
What is the carbon equivalent (CE) and why does it matter?
Carbon equivalent is a formula (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) that predicts weldability. Values below 0.45 generally allow welding without preheat. Higher CE increases the risk of hydrogen-induced cracking in the heat-affected zone, requiring preheat and controlled hydrogen processes.