FEATURE NEWS:
Inline annealing from Niehoff
Niehoff offers continuous inline resistance annealers for various applications. These annealers can process up to 32 wires simultaneously and are specially designed for the many different requirements of non-ferrous metals. During the different stages of the production process, intermediate annealing is necessary to meet the required mechanical properties of the wires.
Inline heat treatment of copper wires by the continuous resistance method consists of pre-heating, main annealing – in which re-crystallization takes place – and in some cases re-heating. When the wire leaves the main annealing zone, it is rapidly quenched in a cooling emulsion, which is then blown off by means of high efficiency compressed air nozzles. To ensure that no residual moisture remains on its surface, the wire is heated once again in the re-heating zone. All the moisture is thus vaporized, and the wire reaches the take-up station in a completely dry condition.
When wires have a diameter of more than 0.25mm, the residual heat in the wire is sufficient to vaporize the moisture. These wires can thus be reliably annealed in just two zones, without the need to expend additional energy. The Niehoff multiwire annealers feature an automatic switchover from two-zone to three-zone annealing modes. The PLC is programmed to automatically effect this switchover based on the individual wire diameter. The benefits are significant energy savings while ensuring a dry wire surface – a critical requirement for downstream processes like extrusion.
Theory and experience have shown that metals with low electrical and thermal conductivity are more difficult to anneal than copper using the continuous electrical resistance annealers designed for copper wire. Niehoff and Bühler came together to offer a solution to this problem through a joint venture company – NBM Niehoff Bühler GmbH.
The RI model inductive continuous annealer is based on the transformer principle.
The primary coil is made of many coil windings while the wire passing in the centre of these windings forms the secondary coil. When electric current flows through the coil windings, an electrical field is induced in the ‘secondary coil’, causing the flow of current which heats up the wire. Varying the frequency of the current and the number of energized coils depending on the alloy, its processing speed and diameter, enables full control
of the annealing process. The wire is quenched in a short legged, high-efficiency cooling zone made of multiple high speed quench nozzles with cooling membrane and after that a drying system with compressed air is used to dry the wire.
The result is a fine-grained, uniform structure with excellent mechanical working properties.
Company: |
Niehoff GmbH & Co. KG |
Country: |
Germany |
Fax: |
+49 91 2297 7155 |
Email: |
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Website: |
www.niehoff.de |