Which type of steel includes additional alloying elements to improve machinability?

The correct answer is Free-Machining Steels because this type of steel is specifically formulated with additional alloying elements, such as sulfur and lead, to enhance its machinability. These modifications reduce tool wear and improve chip formation, which makes machining operations smoother and more efficient.

In contrast, stainless steel, alloy steel, and carbon steel typically do not contain these specific additions aimed at improving machinability. Stainless steel, while durable and resistant to corrosion, can be difficult to machine due to its composition. Alloy steel has a range of alloying elements, but these are often chosen for strength and toughness rather than ease of machining. Carbon steel is primarily made of iron and carbon and lacks the additional elements that would facilitate easier machining processes.