1. Introduction. The wire drawing process may
seem to be simple, but there are crucial issues as lubrication
between die and wire. Failure in lubrication
will give serious surface flaws. The lubricant properties
are influenced by temperature and sheer rate. An
increased temperature will decrease the viscosity of
the lubricant. It is reasonable to assume that the temperature
at the die entrance will be one of the parameters
which determine the amount of lubricant between
die and wire. A drawing machine is fed by electrical
energy, which is transformed to mechanical energy.
In the die this mechanical power is used to reduce the
wire area. A small fraction of the energy is stored in
the wire as dislocation, but most of the energy will
dissipate to heat. The heat may be divided into friction
heat and plastic deformation heat. Thus the highest
temperature will occur in the end of the reduction
zone in the die. At too high temperatures the lubrication
may cease. This temperature is thus very important,
but hard to measure.
Siebel [1] has analyzed the wire drawing process,
and given an analytical equation for drawing force. In
Siebels‘ equation friction force is taken as a fraction
of flow stress. Siebel and Kobitzsch [2] presented an
analytical solution of the temperature in the contact
zone. The wire was assumed to absorb 80 % of the
friction heat. Nilsson [3] tried to use the wire and the
die as a thermocouple. His study indicated a temperature
of about 500°C
[...]
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