CPT International 02/2019

Photos: Klaus Vollrath
carried out in close collaboration with
DGS Druckguss Systeme, which invested
in the plant technology necessary for the
heat treatment.
The material, with a yield strength
(R p0.2
) of 180 - 210 MPa at elongation
values of > 7 %, is described in an internal
Group standard. The test program
for qualification of the component was
extremely extensive, ranging from the
die-casting of test panels for the usual
castability and strength experiments to
the production of real components for
test drives and the determination of
their suitability for the most varied of
joining processes – such as welding,
self-piercing riveting, flow-drilling
screws, gluing and MIG welding.
Development of the
casting process
“The process necessary for producing
thin-walled castings was also specially
developed for the new material,” adds
Axel Schmidt, Technology Manager at
DGS. Simulation programs were extensively
employed during development. This
not only involved the complex geometry/
strength testing as well as the design of
the casting system and mold temperature
control, but also the heat treatment
– because the component’s thin walls
make it highly susceptible to warpage.
Audi was able to make a considerable
contribution towards component tolerance
thanks to its pioneering work in
the field of warpage simulation.Where by
important target criteria were the determination
of the optimum course of the
temperature over time and the method
for storing the castings on special heat
treatment racks. In this connection, a
specific Audi test tool was created as a
thin-walled casting tool. The component
cast in the test tool already had dimensions
of 650 x 650 x 300 mm. The production
of smaller serial parts for the Audi
R8 was another preliminary step.
Advantages of the improved
component
“The main advantages of the newly
implemented component are, above all,
a weight reduction of 19 % and a 50 %
increase in strength (R p0.2
) compared to
the component with the same functions
used in the previous model,” explains
Markus Heim. This was achieved by
means of a weight-optimized design
with thinner walls using the new highstrength
and easy-flowing alloy in combination
with a T6 heat treatment. On the
The fully automated die-casting cell
with dosing furnace, extractor robot
and punch.
Each casting is already provided with an individual
data matrix code in the die-casting
cell, enabling access to all the data regarding
its process and quality parameters.
one hand, this requires a complex
stress-optimized wall thickness and rib
distribution and, on the other hand,
complicated optimization of the casting
process and the molding technology
CASTING PLANT & TECHNOLOGY 2/2019 17