HEAT TREATMENT – FROM STRIP TO FOIL

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HEAT TREATMENT – FROM STRIP TO FOIL Heat treatment is required at several steps during the production of Aluminium foils. This heat treatment is carried out in different heat treatment plants acc. to the re-quirements of the specific process step. The necessary heat treatment processes are intermediate heat treatment during rolling and final annealing of foil rolls at the end of the production process. Aluminium strip is produced from rolling slabs or cast strip. During the production of sheet the feedstock is rolled in several steps. Aluminium strip is also feedstock for the foil production. In order to reduce the hardness of the strip, which results from the rolling process, heat treatment of the rolled material is essential between the rolling processes. Therefore, the coiled strip is intermediately heated in heat treatment plants. At the end of the production process the foil is finally annealed. For these heat treatment processes different furnace concepts are used today: the Multi-Coil Furnace, the Single-Coil Lifting Heart Furnace, and the Multi-Chamber Furnace.

achieve an efficient heat treatment process. By a special charging machine the so like prepared load is placed into the furnace. A Multi-Coil Furnace consists of several sections in which the same process is executed but which can be controlled independently. Each section comes with a circulation fan and a flow distributor including the heating equipment. The upper part of the furnace contains the heat treatment zone including flow distributor and heating; the lower furnace contains the support structure for the load and the space where the charging machine goes in when loading and unloading the furnace chamber. At the front of the furnace a door serves for charging. Usually, several furnaces are installed side by side, which are loaded by one charging machine. The charging machine moves into the area in front of the furnace line. Beside the furnaces preparation, cooling and discharging stands are integrated.

fig.1 Multi-Coil Furnace The Multi-Coil Furnace (see fig. 1) is loaded with several strip coils all at once, which are heat treated by the same heat treatment process. The strip coils are combined to one load on a rack at a preparation station. Equal strip coils – alloy, coil size have to be combined to one load to

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HEAT TREATMENT

Single-Coil Lifting Hearth Furnace Single-Coil Lifting Hearth Furnaces provide individual heat treatment for single strip coils. The Single-Coil Lifting Hearth Furnaces are placed on columns and installed in line; by this the charging machine can move below

the furnaces for placing the strip coil in a furnace (see fig. 2). The individual strip coil is placed in an individual chamber.

fig. 2 For placing a strip coil in the furnace chamber the furnace hearth is transferred to the loading station and the coil will be placed onto the hearth, e.g. by overhead crane. The charging machine is under the furnace hearth, lifts it and moves it into a free furnace. Under the free furnace the charging machine lifts the hearth including strip coil into the furnace. After hearth and coil are placed into the furnace the hearth will be fixed by pins and the furnace sealing will be activated. The lifting unit of the charging car lowers and the charging device is available for discharging or charging another furnace. A heat treated strip coil will be placed on the charging station and from there it can be taken out of the line. For heat treatment the strip coil is supported in accordance with the specific requirements of the production and in a way to avoid marking of the strip. The support structure can be placed on the hearth together with the coil or can be firmly installed and thus become an integrated part of the furnace hearth. All known support structures can be used this way.


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