Furnaces to Handle Any Heat Treat Process

The heat treating process to employ varies depending on what the desired finish product is. Surface Combustion has a wide range of standard and custom thermal processing furnaces that are engineered to handle any heat treat process. We will help you determine the most efficient heat treat process and engineer a furnace to maximize manufacturing time.


Aging furnaces are used to change the properties of certain metals and alloys at ambient or moderately elevated temperatures after hot working or a heat treatment (quench aging in ferrous alloys, natural or artificial aging in ferrous or non-ferrous alloys) or after a cold working operation. The change in properties is often, but not always, due to a phase change (precipitation), but never involves a change in chemical composition of the metal or alloy.


Annealing is a heat treating process that is performed to produce a "soft" structure, consisting generally of small carbides which are evenly distributed in ferrite. This structure provides for lower tensile strength, lower hardness, and high ductility in the material processed. The processing temperature and the rate of cooling depends upon the material being annealed and the purpose of the heat treatment. Basically, annealing furnaces heat metal to and hold it at a suitable temperature before cooling it at a suitable rate.


A group of welding processes that join solid materials together by heating them to a suitable temperature and using a filler metal having a liquidus above 450°C (840°F) but below the solidus of the base materials is completed in a brazing furnace. The filler metal is distributed between the closely fitted surfaces of the joint by capillary action.


Carbonitriding furnaces heat a suitable ferrous material above the lower transformation temperature in a gaseous atmosphere to cause simultaneous absorption of carbon and nitrogen by the surface and, by diffusion, create a concentration gradient. The process is completed by cooling at a rate that produces the desired properties in the workpiece.


Carburizing is the absorption and diffusion of carbon into solid ferrous alloys by heating in a carburizing furnace, to a temperature usually above Ac3, 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, then reaustenitizing and quenching.

Ferritic Nitrocarburizing (FNC)

Ferritic Nitrocarburizing furnaces are used to complete a range of case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures. More Information


The forging process relies on rugged, reliable forging furnaces and thermal processing equipment for the pre-heating of billets, vacuum hardening and nitriding of forging dies, and heat treating of forgings. More Information


Increasing hardness by suitable treatment, usually involving a hardening furnace that heats and cools. When applicable, the following more specific terms should be used: age hardening, flame hardening, induction hardening, laser hardening, precipitation hardening, and quench hardening.


Introducing nitrogen into a solid ferrous alloy by holding at a suitable temperature (below Ac1 for ferritic steels) in contact with a nitrogenous material, usually ammonia is done in a nitriding furnace. More Information


A normalizing furnace heats a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.


The bonding of adjacent surfaces in a mass of particles by molecular or atomic attraction on heating at high temperatures below the melting temperature of any constituent in the material is completed in a sintering furnace. Sintering strengthens a powder mass and normally produces densification and, in powdered metals, recrystallization.


Heating an alloy to a suitable temperature, holding at that temperature long enough to cause one or more constituents to enter into solid solution, and then cooling rapidly enough to hold these constituents in solution is a completed in a solutionizing furnace.


Spheroidizing is an annealing process done in a spheroidizing furnace that produces a round or globular form of carbide in a matrix of ferrite. The cementite (iron carbide) layers of the material are caused by time and temperature to collapse into spheroids, or globules of cementite which is normally required for cold forming processes.

Stress Relieving

Stress relieving furnaces heat to a suitable temperature, hold long enough to reduce residual stress, and then cool slowly enough to minimize the development of new residual stresses.


In heat treatment, reheating hardened steel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing hardness and increasing toughness is done in a tempering furnace. The process also is sometimes applied to normalized steel.

Vacuum Carburizing

Vacuum carburizing furnaces complete gas carburizing process at a high temperature using furnace pressures between 13 and 67 kPa (0.1 to 0.5 torr) during the carburizing portion of the cycle. Steels undergoing this treatment are austenitized in a rough vacuum, carburized in a partial pressure of hydrocarbon gas, diffused in a rough vacuum, and then quenched in either oil or gas. Both batch and continuous furnaces are used.

Other Process Types

Other process types:

Air Quench


Automated Press Quenching

Black Oxide


Bright Annealing


Carbon Baking

Carbon Restoration




Gas Carburizing

Gas Nitriding

Heat Flattening

High Temperature Tempering



Ion (Plasma) Nitriding

Ion Carburizing

Low Pressure Carburizing




Post Oxidation



Press Quenching


Pyrolysis Resource Recovery




Reheating for Press Quench

Scale Free Heating


Solution Treatments

T6 Heat Treatment

Thermal Destruction



Vacuum Heat Treating


Water Quench