About Carbon Steels
Carbon steel is a steel with carbon content ranging from about 0.05% up to 3.8% by weight. Per the American Iron and Steel Institute (AISI), a steel qualifies as a carbon steel when no minimum content is specified for alloying elements such as chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium or zirconium; the specified minimum for copper does not exceed 0.860%; and maximum manganese, silicon and copper contents stay within set limits.
AISI Carbon Steel Criteria
- No minimum content specified for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, or zirconium
- Specified minimum copper content does not exceed 0.860%
- Maximum content stays within limits for manganese (1.65%), silicon (0.60%) and copper (0.60%)
Carbon Steel Classifications
| Classification | Carbon Content | Key Properties & Typical Uses |
|---|---|---|
| Low-Carbon Steel | 0.05% – 0.25% | Plain carbon steel; most ductile and weldable grade — widely used structural and sheet steel |
| Medium-Carbon Steel | ~0.3% – 0.5% | Balances ductility, strength and wear resistance; used for large parts, forgings and automotive components |
| High-Carbon Steel | ~0.6% – 1.0% | Very strong; used for springs, edged tools and high-strength wires |
| Ultra-High-Carbon Steel | ~1.25% – 2.0% | Can be tempered to great hardness; used for specialty knives, axles and punches (above 2.5% carbon, powder metallurgy is typically used instead) |