Heat Treating Terminology

Air Hardening Steel - A steel containing sufficient carbon to harden fully during cooling in air from a temperature above its transformation range.

Annealing - Heat treat process consisting of heating to and holding at a temperature above the transformation temperature followed by slow cooling in the furnace at a suitable rate primarily for the purpose to soften metallic materials.

Batch Furnace - Batch Oven - Terms referring to equipment for a variety of thermal processing operations involving batch processing of materials.  "Batch" refers to the part(s) being brought to the furnace/oven.  Lucifer Furnaces builds a huge variety of thermal processing equipment that meets the need of batch processing.

Brazing - A heat treat process that joins solid materials together by heating them to a suitable temperature using a filler metal.

Bright Annealing - A process of annealing usually carried out in a controlled furnace atmosphere so that surface oxidation is reduced to a minimum and the surface remains relatively bright.

Carburizing - A form of case hardening that produces a carbon gradient extending inward from the surface, enabling the surface layer to be hardened either by quenching directly from the carburizing temperature or by cooling to room temperature.

Decarburization - Loss of carbon from the surface layer of the alloy due to reaction with one or more chemical substances which contact the surface.

Hardening - Heat treat process to increase hardness by heating and cooling. The formation of martensite in alloy when quenched rapidly from a temperature above the transformation temperature.

Industrial Ovens - Heat treat equipment  to cure, bake and dry materials in laboratories or production facilities.  Generally ovens for thermal processing are equipped with fans for air recirculation/uniform heating.

Induction Heating - Heating by combining electrical resistance and hysteresis losses induced by subjecting a metal to the varying magnetic field surrounding a coil carrying alternating current.

Normalizing - A heat treat process consisting of heating to a temperature above the transformation range followed by rapid cooling in air. Normalizing refines grain size, relieves internal stresses and makes a material more uniform for better machinability.

Preheating - Heating to an intermediate temperature before either further thermal or mechanical treatment or before final austenitizing.

Protective Atmospheres - Gases used to displace the oxygen in the heating chamber to prevent or minimize scale and oxidation on the surface of the work. Atmosphere can also be used to add carbon or remove carbon from the surface of steels. Protective atmospheres are generally classified as being inert (Nitrogen, Argon) or reducing (Hydrogen, Dissociated Ammonia.) Reducing atmospheres are flammable and explosive and require additional safety equipment for operation with furnaces.

Quenching - Rapidly cooling metal alloys for hardening. Typical quench mediums include air, oil, water, salt and polymers.

Sintering - Heat treat process which bonds powdered metals under high temperatures but below the melting temperature of the material.

Stress Relieve - A heat treat process consisting of heating steel below the transformation temperature, to relieve internal stresses, followed by slow cooling.

Tempering - A heat treat process consisting of reheating a quenched steel at a temperature below the transformation range to decrease hardness and increase toughness and ductility.

Transformation Temperature - The temperature at which a change in the molecular structure of the steel occurs. The transformation temperature varies depending on the carbon and alloy content of the steel.

TUS - Temperature Uniformity Survey