A vacuum furnace is an enclosed structure that produces heat for
industrial purposes; most common is the treatment of steel alloys. This
type of heat treating process takes place in a vacuum, or airtight,
enclosed structure which alleviates surface reactions. The lack of air
and other gases in the enclosure prevents these items from becoming a
source of contamination. Vacuum furnaces are able to heat various metals
to high temperatures and perform processes such as brazing, sintering
and heat treatment under precise and controlled conditions with high
consistency and low contamination.
Vacuum furnaces are ideal for processing parts for bright annealing, stress relieving, normalizing, tempering, degassing, brazing and other industrial purposes in which high pressure cooling or quenching mediums are used. Typically, vacuum furnaces use low atmospheric pressure for heating. The use of vacuum furnaces for heating applications provides a number of benefits. First, vacuum furnaces have the capability of controlling temperature within a small area. The furnace is able to keep the temperature uniform throughout the enclosure, making it ideal for metals that are sensitive to variations in temperature. Due to their use of a vacuum, they also offer low contamination of the product by carbon, oxygen and other gases. Further, because oxygen is removed in a vacuum, oxidation is unable to occur. Vacuum furnaces also use quenching, providing quick cooling of the product. If chosen, the process can also be controlled by a computer in order to ensure metallurgical repeatability.
Important factors to consider when selecting a vacuum furnace are its pressure range, process temperature, control systems, chamber length, single/multiple chamber, height, width and outer tube diameter. Pressure range represents the range of pressure the furnace can run on. Meanwhile process temperature is the range of temperatures the furnace employs. Control systems refer to the technology that makes it easiest to monitor and control the variable, making the process run smoothly. The length of the chamber is the length of the furnace; there can also be a single or multiple chambers, depending on what the vacuum furnace is being used for. Height and width are measured using internal measurements of the furnace.