Chemical element making brittle the steel by its tendency to thicken the grain and decrease the plasticity of the ferrite. In small percentages (<0.10%) it can cause an increase in hardness and tensile strength to the detriment of toughness. For this reason it is an element that must be minimized in steel; different standards limit it with maximum percentages of 0.03.
It can be used as an alloying element in low carbon free cutting steels (in contents lower than 0.11%), in order to make brittle the basically ferritic matrix, resulting in a better chip removal in the machining.