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. 

Brazing - Heat treat process that joins solid materials together by heating them to a suitable temperature using a filler metal with a liquidus temperature below the solidus temperature of the base materials.

Carburizing - Diffusion of carbon into solid ferrous alloys by heating to desired temperature in contact with a suitable carbonaceous material. 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 which increases hardness by heating and cooling. The formation of martensite in alloy when quenched rapidly from a temperature above the transformation temperature.

Industrial Ovens - Heated chambers to cure, bake and dry materials in laboratoaries or production facilities.

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 - Heat treat process consisting of heating to a temperature above the transformation range followed by rapid cooling in air. Normalizing refines grain size and makes structure 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 - Hardening alloys by heating above the transformation temperature and then cooling at a rate to transform the austenite to martensite. 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 - Heat treat process consisting of heating steel below the transformation temperature to relieve internal stresses followed by slow cooling.

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

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.