Which type of carbon steel would be used in a spring or a file or metal cutting saw?

• A. Lower carbon steels
• B. Medium carbon steels
• C. Higher carbon steels
• D. Ultra-high carbon steels

Answer: (C)

Hardness and edge retention come from higher carbon content in steel. When steel has more carbon, it can be heat-treated to be very hard, which is essential for tools that must hold a sharp edge and resist wear. A file needs to stay sharp as it files metal, and a metal-cutting saw blade must maintain its edge through repeated use. A spring, while needing to resist deformation, also benefits from enough hardness to return to shape after bending, provided it isn’t so brittle that it cracks. Lower carbon steels are too soft for keeping an edge and wear resistance. Medium carbon steels are stronger but don’t reach the hardness of high-carbon grades. Ultra-high carbon steels can be extremely hard yet brittle, making them less suitable for springs and common edged tools. So, higher carbon steel is the best match for springs, files, and metal-cutting saws.