What characteristic defines medium-carbon steels?

Medium-carbon steels are characterized by a balance of carbon content, typically ranging from about 0.3% to 0.6% carbon. This carbon level contributes to the steel's mechanical properties, making it harder than low-carbon steels, which usually have a carbon content below 0.3%. The increased hardness of medium-carbon steels enhances their strength and performance under various mechanical stresses, making them suitable for applications such as automotive components, machinery parts, and tools where enhanced durability is required.

In this context, while medium-carbon steels do possess a measure of ductility, their distinctive trait in comparison to low-carbon steels is the increased hardness attributable to the higher carbon content. The option stating they have higher weldability than low-carbon steels is inaccurate, as medium-carbon steels can be more challenging to weld due to their propensity for hardening and potential for cracking in the heat-affected zones.