STRIP AND STRAND ANNEALING FURNACES
The strip annealing furnace can be designed to process a single wide strip or multiple parallel narrow strips within a heating chamber. In nearly all annealing furnaces heat resisting alloy muffles are provided to contain an oxygen-free, dry, controlled protective atmosphere to prevent oxidation of product surfaces at elevated temperatures. Multiple strip furnaces are usually supplied with parallel muffles mounted across the width of the heating chamber which extend completely through the furnace and further in open air at both ends where they are flanged and attached gas-tight to the purge chamber at the front and the cooling chamber at the rear. The heat resisting alloy muffle cross-section is available as cylindrical, oval, D-shaped, diamond or special as required by the process.
The strip annealing furnace can be designed with a single heating chamber with parallel muffles or with multiple parallel heating chambers thermally isolated from one another. Each chamber would then be provided with independent dedicated thermocouples, temperature controllers and power controllers.
Thus, line speed and control temperature can be maintained independent of the adjacent parallel chambers. This will extend the versatility of the furnace to enable processing of different materials, product thickness and product load through the independent muffles simultaneously.
To increase furnace capacity heating chamber length can be extended but it is advisable to divide each overall chamber length into independently controlled multiple zones to assure repeatable control of heating profiles.
The strand annealer consists of a series of parallel alloy pipes mounted across the width of the heating chamber. The pipes extend completely through the furnace box and further in open air beyond the front and rear wall of the box. Metallic wire of varying cross-section passes through the hot furnace at varying speed within the alloy tube which is filled with a protective atmosphere to preclude formation of oxides on product surfaces during the annealing process.
Gas flow into each tube can be individually monitored and controlled through a flow control panel. The alloy tubes will terminate in a manifold block. Cooler tubes connected to the block outlet will pass through a common water-jacket to allow the product to cool within the controlled atmosphere to secure bright results.
Vertical strand annealers are provided for products which require a rapid liquid quench. The tube discharge extends below liquid level to provide an effective atmosphere seal and assure bright product. Immersed rollers redirect multiple wire strands out of the tank to rewind. The vertical furnace heating chamber is divided into multiple zones. Each zone interface is provided with an insulated thermal barrier which will enable control temperature maintenance within the zone and preclude thermal migration to upper chamber elevations. This will assure that the product will undergo the specified heating profile and insure that it can be duplicated precisely for the life of the equipment.