Shaft-type Heat Treatment Furnaces
These furnaces are used for the heat treatment of steel forgings, mainly shafts and rotors, bulky symmetrical products, such as nuclear reactor vessel annuluses, small parts in baskets or on pallets or for annealing coiled sheet metal or wires made of steels or nonferrous metals, mainly copper and brass. These shaft-type furnaces have gas-fired or electrically-fired heating systems, with protective atmospheres where necessary. Operating temperatures range up to 1,100°C, depending on the use. In case of lower temperatures and with an electrical heating system or an indirect gas-fired heating system, a circulation fan with baffles that channel the airflows inside the furnace is used to achieve desirable uniformity of the temperature field.
For annealing, the charge in baskets or arranged in coils is put into the furnace by means of pallets and supporting frames whereas shafts are mostly fastened onto special hangers passing through the furnace lid and suspended on bearing supports above the lid.
With a limited height of hall and of crab crane, these shaft-type furnaces may sometimes be used instead of bell furnaces.
An optional approach for the heat treatment of shafts and rotors in the upright position is available in vertical tower-type furnaces. These are situated vertically above the hall ground level and are filled with charges from the side.