Free cutting steel, also refers as the free-machining steel, is the alloy steel by the addition of one or more free cutting elements such as sulfur, phosphorus, lead, calcium, selenium and tellurium to improve its cutting property. Free cutting steel is characterized by its excellent cutting performance. These elements in steel reduce the cutting resistance and the abrasion of machined parts, improve the machinability for its lubricating effect.
There are several classifications of free-cutting steel: S- free cutting steel, Pb-free cutting steel, Ca- free cutting steel and composite free cutting steel according to the different free cutting elements; automatic free cutting steel, structural free cutting steel and special free cutting steel (heat resistant steel, stainless steel, tool steel, etc.) according to its uses.