Perfect annealing for difficult applications
During thewire drawing process, the microstructure of the wire becomes harder. In order to reverse this effect, the wire must be annealed. In modern wire drawing lines, the wire, after leaving the drawing zone is passed through an electrically operated annealer and then cooled and spooled. Maschinenfabrik Niehoff, one of the internationally leading manufacturers of wire drawing machinery, builds in-line annealers whose working principle is adapted to the characteristics of wires made of copper, aluminum and other non-ferrous metals. For wires made of metals with a low electrical and thermal conductivity, the continuous working inductive and conductive annealers of the “RI series” are very well suited. The annealing energy is induced into the wire without contact. The “RI 420” version, the largest model of the series, is designed for wires in the range from 2.0mm to 4.6mm diameter and can reach annealing termperatures of up to 1,000°C.
The RI annealers are the result of a development process initiated more than ten years ago by the Niehoff joint venture company NBM. Since April 2011 they have been built and further developed by Maschinenfabrik Niehoff. The annealers work on the principle of an excitation voltage transformer with magnetic cores acting as “primary coil” and the wire moves contactlessly through them. The wire passes through the annealer forming a wire loop which is closed using the short circuit pulley. By applying an alternating current to the magnetic coils, a voltage is induced into the wire loop. This voltage causes a short-circuit current that heats the wire. The annealing process is achieved under an inert protective gas in order to avoid any oxidation of the wire surface. In the cooling section, the wire is quenched and its temperature rapidly reduced by applying coolant.
Good forming properties, high surface quality
Because of rapid cooling, a very fine-grained, homogeneous structure can be achieved that gives the wire excellent processing and forming properties. Additionally, these wires have a high surface quality. With RI annealers, soft flat wire can be produced which is used for photovoltaic applications. RI annealers can be combined with rolling lines, drawing lines and combined lines and are suited for round, flat and profile wires with a simple cross-section. The annealers are suited for copper wires; the main application, however, is annealing of wires made of non-ferrous metals with a low electrical and thermal conductivity, e.g. copper alloys like CuZn (brass), CuSn, CuNiZn (German silver) as well as low-alloyed copper alloys such as CuMg, CuBe, CuCr and CuSiMn. The RI annealers can also be used to perfectly anneal wires made of heating conductor and resistance alloys such as nickel, copper nickel and nickel chrome as well as tin or silver plated copper wires, wires made of precious metals and their alloys and wires made of metallic compounds. By means of a calculation program Niehoff is able to simulate the annealing of wires made of different materials and with different dimensions. For each application consumption value, annealing velocities, wire temperatures and other parameters can be determined in advance.
Easy handling
The RI annealers are characterized by a simple and clear design. The wire path is achieved by using only two deflections, one at the short circuit pulley near the wire inlet at the bottom, the other at the upper part on a deflection pulley or a roller bow depending on the annealer model. The position of the short-circuit pulley is adjustable to allow exact alignment of the wire path into the cooling section. The few wear parts of the annealer have a long service life. The individual elements can be taken out easily and quickly for cleaning or for replacement using minimal tooling. The short circuit pulley is driven in order to reduce the drag forces acting on the heated wire. Furthermore, the RI annealers are operated with a separate haul-off unit. This way the wire tension in the annealer can be controlled individually, and wire tension fluctuations caused by the spooler have no disturbing influence on the annealing process.
The RI 420 annealer adheres – like all the other modern annealers of the RI series – to the current safety regulations of the machinery directive RL 2006/42/EG. As as result of the contactless energy transfer principle, an energy efficiency of 80% to 90% is achieved.
Annealing machine http://www.jspoly.com/en