Vacuum furnace

This article's lead section contains information that is not included elsewhere in the article. If the information is appropriate for the lead of the article, this information should also be included in the body of the article. (August 2024) (Learn how and when to remove this message)

A vacuum furnace is a type of furnace in which the product in the furnace is surrounded by a vacuum during processing. The absence of air or other gases prevents oxidation, heat loss from the product through convection, and removes a source of contamination. This enables the furnace to heat materials (typically metals and ceramics) to temperatures as high as 3,000 °C (5,432 °F) ^[1] 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, sintering and heat treatment with high consistency and low contamination.

Characteristics of a vacuum furnace are:

• Uniform temperatures in the range. 800–3,000 °C (1,500–5,400 °F)
• Commercially available vacuum pumping systems can reach vacuum levels as low as 1×10⁻¹¹ torrs (1.3×10⁻¹¹ mbar; 1.3×10⁻¹⁴ atm)
• Temperature can be controlled within a heated zone, typically surrounded by heat shielding or insulation.
• Low contamination of the product by carbon, oxygen 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) 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 oxidation, which is undesirable. A vacuum furnace removes the oxygen and prevents this from happening.

An inert gas, such as Argon, is often used to quickly cool the treated metals back to non-metallurgical levels (below 400 °F [200 °C]) after the desired process in the furnace.^[2] 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 to remove heat. This process continues until the desired temperature is reached.