Electrically heated salt bath crucible furnaces for uniform and fast heat treatment of work pieces and tools under exclusion of air.
A Salt Bath is a largely overlooked alternative to many types of furnace. It has many advantages and a few disadvantages over conventional atmosphere furnace. The heating medium of a salt bath is the salt itself. This is heated to the required temperature by either external heating, over the side submerged elements, or submerged electrodes. When a load is submerged into the salt it is heated rapidly and uniformly to the required temperature. The salt also doubles as a protective atmosphere during the heating cycle. When the load is withdrawn a thin covering film of salt will protect it.
Temperatures available can range from around 1300C and 600C. The low temperature ranges can be heated by external heating to a salt pot, or over the side submerged sheathed wire elements. Above 6000c, over the side submerge elements suffer severely from corrosion at the salt-air interface (where the elements/electrode enter the salt). At these temperatures and above we recommend totally submerged electrodes, which enter the bath through the side-wall (below the salt-air interface) and apply heat by using the salt itself as the resistance element. This method has many advantages over any heating method that enters the bath over the side wall. Not only does it eliminate the electrode corrosion at the salt-air interface, but also reduces the top losses (heat escaping from the top of the bath) because the bath can be smaller. It also aids salt circulation and agitation due to electro-dynamic forces.
Some processes will require other equipment to complement the Salt Bath.
Salt bath heat treatment is a heat treatment process comprising an immersion of the treated part into a molten salt (or salts mixture).
* Benefits of heat treatment in salt baths
* Compositions of salt baths
* Heat treatments conducted in salt baths
Benefits of Salt Bath Furnace
* Fast heating. A work part immersed into a molten salt is heated by heat transferred by conduction (combined with convection) through the liquid media (salt bath). The heat transfer rate in a liquid media is much greater than that in other heating mechanisms: radiation, convection through a gas (e.g., air).
* Controlled cooling conditions during quenching. In conventional quenching operation either water or oil are used as the quenching media. High cooling rate provided by water/oil may cause cracks and distortions. Cooling in molten salt is slower and stops at lower temperature.
* Low surface oxidation and decarburization. The contact of the hot work part with the atmosphere is minimized when the part is treated in the salt bath.