Furnace evacuated by mechanical and diffusion pumps to around 0.001 torr or better, heated by graphite or molybdenum elements in a hot zone, then cooled by backfilling nitrogen or argon at 2 to 20 bar with a fan, or by dropping into oil. Parts come out bright and free of decarburization. It is standard for tool steels, aerospace alloys, vacuum brazing and low-pressure carburizing.
D2 dies go in the vacuum furnace, 6-bar nitrogen quench, double temper, and they come out bright.
Run a leak-up rate check before critical loads; a small leak shows up later as tinted parts and failed brightness.
Also heard as
- vac furnace
- vacuum
Related terms
Bright
Describes parts that come out of the furnace clean and unoxidized, with no scale or discoloration.
Air hardening
Describes steels with enough alloy to harden fully when cooled in still air or gas instead of a liquid.
Vacuum carburizing
Carburizing at low pressure in a vacuum furnace using pulses of hydrocarbon gas, then a gas or oil quench.
TUS
Temperature uniformity survey: a test mapping how evenly a furnace holds temperature across its work zone.