A vacuum furnace is a type of furnace in which the product in the furnace is surrounded by a

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often ...

during processing. The absence of air or other gases prevents

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

, heat loss from the product through

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...

, and removes a source of contamination. This enables the furnace to heat materials (typically metals and ceramics) to temperatures as high as with select materials. Maximum furnace temperatures and vacuum levels depend on melting points and vapor pressures of heated materials. Vacuum furnaces are used to carry out processes such as annealing,

brazing Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from ...

sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...

and

heat treatment Heat treating (or heat treatment) is a group of industrial process, industrial, thermal and metalworking, metalworking processes used to alter the physical property, physical, and sometimes chemical property, chemical, properties of a material. ...

with high consistency and low contamination. Characteristics of a vacuum furnace are: * Uniform temperatures in the range. * Commercially available vacuum pumping systems can reach vacuum levels as low as * Temperature can be controlled within a heated zone, typically surrounded by heat shielding or insulation. * Low contamination of the product by carbon,

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

and other gases. * Vacuum pumping systems remove low temperature by-products from the process materials during heating, resulting in a higher purity end product. * Quick cooling (

quenching In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as ...

) of product can be used to shorten process cycle times. * The process can be computer controlled to ensure repeatability. Heating metals to high temperatures in open to atmosphere normally causes rapid

, which is undesirable. A vacuum furnace removes the oxygen and prevents this from happening. An

inert gas An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. The noble gases often do not react with many substances and were historically referred to ...

, such as

Argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice a ...

, is often used to quickly cool the treated metals back to non-metallurgical levels (below ) after the desired process in the furnace. This inert gas can be pressurized to two times atmosphere or more, then circulated through the hot zone area to pick up heat before passing through a

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

to remove heat. This process continues until the desired temperature is reached.

Common uses

Vacuum furnaces are used in a wide range of applications in both production industries and research laboratories. At temperatures below 1200 °C, a vacuum furnace is commonly used for the heat treatment of

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...

alloys. Many general heat treating applications involve the hardening and tempering of a steel part to make it strong and tough through service. Hardening involves heating the steel to a predetermined temperature, then cooling it rapidly in water, oil or suitable medium. A further application for vacuum furnaces is Vacuum

Carburizing Carburising, carburizing (chiefly American English), or carburisation is a heat treatment process in which iron or steel absorbs carbon while the metal is heated in the presence of a carbon-bearing material, such as charcoal or carbon monoxide. ...

also known as Low Pressure Carburizing or LPC. In this process, a gas (such as acetylene) is introduced as a partial pressure into the hot zone at temperatures typically between . The gas disassociates into its constituent elements (in this case carbon and hydrogen). The carbon is then diffused into the surface area of the part. This function is typically repeated, varying the duration of gas input and diffusion time. Once the workload is properly "cased", the metal is quenched using oil or high pressure gas (HPGQ). For HPGQ, nitrogen or, for faster quench helium, is commonly used. This process is also known as

case hardening Case-hardening or surface hardening is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal at the surface. For iron or steel with low carbon ...

. Another low temperature application of vacuum furnaces is debinding, a process for the removal of binders. Heat is applied under a vacuum in a sealed chamber, melting or vaporizing the binder from the

aggregate Aggregate or aggregates may refer to: Computing and mathematics * collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...

. The binder is evacuated by the pumping system and collected or purged downstream. The material with a higher melting point is left behind in a purified state and can be further processed. Vacuum furnaces capable of temperatures above 1200 °C are used in various industry sectors such as electronics, medical, crystal growth, energy and artificial gems. The processing of high temperature materials, both of metals and nonmetals, in a vacuum environment allows annealing,

, purification,

and other processes to take place in a controlled manner.

Vacuum furnace parts

Vacuum furnace parts are utilized in a wide range of industries. A vacuum furnace repair is one approach for shielding hot steel and metal parts from the detrimental effects of an air environment. A vacuum furnace parts are typically an electrically heated furnace that maintains a vacuum throughout the operation. Electric resistance components made of graphite, ceramics, or metals heat the majority of vacuum furnace parts.

References

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vacuum furnace parts
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