Open Fire Hardening
Open Fire Hardening is produced in most steels by rapid cooling via liquid bath from above their respective transformation temperatures. Steel is rarely used in its fully hardened condition because its associated brittleness makes it unsuitable for most purposes. Hardening is almost always followed by tempering - an operation which restores some toughness at a cost of some loss of hardness. Any tempering operation involves a degree of stress relieving - the residual stresses produced during hardening are relieved as the tempering temperature increases the mobility of the microconstituents The higher the temperature, the greater the stress relief, and generally speaking, the softer the steel. NATIONAL HEAT TREAT has 2 furnaces for Open Fire Hardening.