Below is a list of Vacuum Furnaces manufacturers from Ashland, Ohio. 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.