Which range corresponds to high carbon steel?

• A. 0.45-0.75%
• B. 0.30-0.45%
• C. 0.75-1.50%
• D. 0.05-0.30%

Answer: (A)

Carbon content controls steel properties: as carbon increases, hardness and strength rise while ductility and weldability fall. High carbon steel is defined by roughly 0.45 to 0.75 percent carbon. At this level you get significantly harder, more wear-resistant steel that’s well suited for tools, blades, and springs, yet still has enough toughness for practical use and isn’t as brittle as very high carbon varieties.

Lower carbon ranges (about 0.05 to 0.30%) produce very ductile, weldable steels that are easy to form. The middle range (roughly 0.30 to 0.45%) offers greater strength than mild steel but remains workable. Ranges above the high-carbon window (roughly 0.75 to 1.50%) shift toward very high carbon or tool steels, which are extremely hard but can be brittle and are tougher to weld.