They are steels with a Boron content between 0.0008-0.005%.
The precipitation of boron in the austenite grain joints delays the appearance of ferrite and favors the appearance of bainite or martensite in tempering treatments.
The boron steels have a good suitability for cold deformation and enough hardenability to ensure the mechanical characteristics required after quenching and tempering. They allow to remove other alloying elements and to avoid softening treatments – made in steels without boron (in Cr, CrMo or CrNiMo, CMn) because of the difficulties of making in the cold forging.
Their most common applications are the manufacture of medium and high strength screws, in agriculture, public works, tools, blades and supports.