EOW May 2007

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EuroWire – May 2007 114
Heat and surface
treatment systems
For physical reasons, wire must be
annealed during the drawing process. For
certain applications a surface treatment is
also necessary. Maschinenfabrik Niehoff
GmbH & Co KG, Germany offers a range of
continuous annealers and galvanic plating
lines for wire made of copper, aluminium
and other non-ferrous metals and their
alloys.
Wire made of copper and copper alloys
is normally continuously annealed
immediately following the drawing
process, in an annealer which is integrated
into the drawing line. The wire is fed over
contact pulleys, which induce an electrical
voltage. A defined current flows as a result
of the inherent resistance of the wire
material causing the wire to heat up.
Niehoff has developed annealers for
various applications. The product line
incudes systems that process between
1 and 42 wires with diameters ranging
from 0.05mm to 8mm. In practice, heat
treatment during continuous annealing
of copper wire consists of a pre-heating,
the main annealing, and sometimes post-
heating. As a result, the annealing sections
in the annealers are designed as a three-
zone circuit.
After the wire has passed through the
main annealing section, it is cooled using
a coolant, which is then removed with
forced air emitted by air jets. In order to
remove any moisture residue on the wire
surface, the wire is heated again in the
third zone. However, if the wire diameter
is greater than 0.20mm, the residual heat
in the wire is sufficient to evaporate the
moisture. Consequently, this wire can be
reliably annealed in a two-zone circuit
without any additional supply of energy.
The RM series annealers from Niehoff are
able to switch automatically between two
and three-zone annealing according to
the wire diameter, thus avoiding energy
wastage.
The company has also developed an inline
annealer for use in the production of wire
made of EC aluminium and numerous
aluminium alloys. Because aluminium has
a strong tendency to oxidise, continuous
resistance annealers for aluminium wire
must be designed so that no oxygen can
enter during the heating process.
The Niehoff Bühler NBM joint venture
company has developed RI type inductive
continuous annealers. These operate on
the basis of the induction principle, and
are suitable for wire with low electrical
and heat conduction characteristics, such
as wire made of various copper alloys. This
kind of wire is very difficult to anneal in
resistance continuous annealers designed
for copper. The RI annealers create wire
with a fine grained, homogeneous
microstructure that gives it very good
processing and forming properties. RI
annealers can be combined with rolling
systems and drawing systems, and are
suitable for round, flat and profile wires
with a simple cross-section made of
brass, bronze and German silver, as well
as nickel and nickel alloys such as heating
conductor and resistance alloys.
The process for plating copper alloy wires
realised in continuously working galvanic
plating lines must generate a tight plating
with homogeneous physical properties
and a high surface quality along the
whole wire length. Modern plating lines
for copper alloys must meet demanding
technical, ecological and economical
requirements.
Maschinenfabrik Niehoff and Steuler
Anlagenbau, a manufacturer of surface
treatment plants, combined their
experience to develop the Niehoff-Steuler
WPT wire plating technology and to
manufacture galvanic wire plating lines
for tin plating, tin-lead plating, nickel
plating, silver plating, and zinc plating
of non-ferrous metal wires. Advantages
of WPT lines include complete solutions
without interface problems, minimised
consumption of energy, water and
chemicals, up to 100% usage of anode
materials, and automatic dosing of
additive and supply of water.
Maschinenfabrik Niehoff GmbH
& Co KG – Germany
Fax: +49 9122 977 155
Email:
Website:
Anode basket with anode material ▲
equipment for wire treatment