Metal treatment – Process of modifying or maintaining internal physical... – With measuring – testing – or sensing
Patent
1995-04-05
1997-12-23
Ip, Sikyin
Metal treatment
Process of modifying or maintaining internal physical...
With measuring, testing, or sensing
148511, 148566, 148576, 266 90, 266 92, 266104, 219155, C21D 962
Patent
active
057003351
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process and a device regulating the calorific output in a resistance annealing plant.
Description of Related Art
A continuous resistance annealing and processing line is used for subjecting continuously cast metal products to heat treatment, the term "continuously cast metal products" here denoting wire made of ferrous and nonferrous metals, in particular copper, but also bundles of parallel, twisted or stranded wires made of these materials. To simplify matters, the term "wire" is used for characterizing these products in this document.
In a continous annealing and processing line the wire is led over at least two contact elements having a different voltage potential, such that a current runs through the wire resulting in its heating. Preferably rotating rollers are used as contact elements, having a circumferential speed principally equal to the passing speed of the wire; however, electrolytes and molten metal baths as well as fixed contact elements may be used. The problems of regulating the calorific power in such a continous annealing and processing plant and the solution as provided for by this invention are detailed in the example of a three-phase current annealing plant for thin copper wires. However, using this example shall in no way be understood as a limitation of the applicability of the present invention to resistance annealing plants in general, rather may the invention also be used for other continous annealing and processing plants, such as DC annealing plants.
As is generally known, flexible electric lines normally have copper strands, manufactured of individual wires having a diameter of e.g. 0.2 mm. In case one or several of these individual wires of the strand break during use, not only the electric conductivity is impaired, but in particular the danger arises that individual wires penetrate the electric insulation, resulting in a considerable danger of accidents.
Therefore the mechanical quality of such strands, in particular the fatigue strength under reversed bending stresses has to meet high requirements which have been laid down by VDE (Association of German Electrical Engineers) in the Federal Republic of Germany.
If the copper wire used for manufacturing brands is drawn to its final diameter in a wire drawing machine, the metal structure changes and the wire becomes hard and brittle and has only a low fatigue strength under reversed bending stresses. In order to give the wire the desired mechanical properties, it is subsequently subjected to a heat treatment in a continous annealing and processing plant. To guarantee the desired quality, the achieved annealing temperature of the wire has to be within a strictly defined temperature range, and if the temperature falls below this range or exceeds it, this results in a quality impairment and--as a consequence--in refuse.
In order to assure that the desired temperature range is reached, it would be advantageous, if the temperature of the passing wire could be measured exactly. However, this meets with difficulties as--on the one hand--the wire runs through the wire annealing plant at high speed (e.g. 10-30 m/s) and--on the other hand--the wire surface is very small due to the small diameter, such that here the prior art methods for measuring the surface temperature will not be successful.
As described in DE 40 10 309 C1 the regulation of such continous annealing and processing plants is therefore performed via regulating the calorific power according to the equation at which the wire passes through the continous annealing and processing plant and G being the so-called annealing factor, a product- and plant-specific value. Normally the output regulation is performed by means of thyristors in antiparallel connection, whose firing angle is controlled adequately.
Although this prior art regulation process and this prior art regulation device works satisfactorily in many applications it turned out that a further quality increase in the ultimate product is not possible, in
REFERENCES:
patent: 3842239 (1974-10-01), Ellinghausen et al.
"Elektrische Ausrustungen fur Widerstands-Drahtgluhanlagen", N. Bardahl, Draht, vol. 20, No. 6, 1969, Bamberg, Germany, pp. 390-395.
Ip Sikyin
Maschinenfabrik Niehoff GmbH & Co. KG
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