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TECHNOLOGY
possible distortion”, says Mr Belte.
As already outlined earlier, the quenching
process is also important if the components
are to cool as uniformly as possible. The
quench media used are air, water and polymer
solutions. Which quenching media are
chosen depends on the component, its geometry,
and the mechanical properties to be produced
in it. For example, polymer quenching
is interesting for complex components such
as crank-cases. Structural components such
as longitudinal support members, which have
a large surface area with only comparatively
low mass, can be effectively air-quenched. At
Belte air cooling is called HISAQ (High Speed
Air Quenching), i.e. quenching in air at a high
rate. In 2003 Belte applied for a patent for this
development for the heat treatment of gravity
and pressure diecast components.
Development work on radiated
heat instead of air circulation
Typically, heat treatment is carried out by
convection. The furnaces are designed so that
the furnace chamber is heated by air circulation
and the components come in contact with
the hot air. At present the company is testing
a new method in which the components are
irradiated directly by infra-red radiation. “In
this way the components can be brought to
temperature very quickly and with pinpoint
accuracy: almost in a few minutes,” says Dan
Dragulin, head of R&D at Belte AG. Such
tests started for Audi already three years ago.
The important factors in heat treatment
are always mechanical properties, but also the
cost. “In a large furnace chamber with convection
heating the heat-up phase takes 45
minutes or more, for example in a continuous-throughput
unit for cylinder heads. With
infra-red heating, in test runs we managed to
bring such components to temperature within
seven minutes. In this way I can not only
shorten the dwell time in the furnace, but
achieve even better mechanical properties
due to the rapid heating,” stresses Mr Belte.
For the test results on a structural casting for
Audi, see the following report.
This process is still at an early stage of testing.
Whether and in what form the process
will in the future become marketable, is not
yet clear. However, the development work
so far indicates “that we are not a classical
service provider which carries out heat treatment
according to specification, but that we
always strive to develop our processes further,”
stresses Mr Belte.
■
Infrared heat transfer for thin-walled aluminium automotive castings
A novelty in the field of aluminium high pressure die casting
demonstrating the high versatility of aluminium as all around material
D. Dragulin, M. Belte, Belte AG
Fig. 1: Casting exposed to IR – between arrows: the zone under direct exposure
to radiation; distance between casting and IR-module: left: 10 cm, right: 30 cm
Fig. 2: Inappropriate position of the casting within the IR-module
© Belte AG
Preamble
The use of infrared radiation in the field of
aluminium processing enables easier automation
and control of the heat transfer processes
and contributes to productivity enhancement.
The electrical hardware of the
infrared module allows for drastic improvements
in the efficiency factor of the industrial
equipment used for aluminium processing,
while also reducing the pollution degree.
Dr. Dimitrie Popescu, Associate Professor, Old
Dominion University, Norfolk, Virginia, USA
Abstract
The application of infra-red radiation to heat
treatment of thin-walled aluminium high pressure
die castings is a process that is in the
early stages of its development. The objective
of the experiment presented here was to analyse
the heating rate of the casting and to study
its corresponding mechanical properties. All
experiments were realised using Audi-structural
castings.
Experimental conditions
The casting process was realised by Trimet.
• IR module
Ground coverage: 108 kW
• Casting
• Weight: 2.5 kg
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