Technology News
96
M
arch
2014
New casting material for low-
temperature applications
PARTICULAR demands are placed
on steels that are used in the low
temperature range: they have to
withstand temperatures down to -196°C.
To date, austenitic steels have been
used. However, because of their low
yield strength, these are subject to
the risk of early deformation and must
therefore be cast with very thick walls.
This was the starting point for the
development of the new low-temperature
material Dux Cryo
®
, which displays higher
strength values with good toughness.
The advantage for use is that the casting
can be constructed with thinner walls,
saving both weight and costs.
Instead of austenitic steel, Schmolz
+ Bickenbach Guss has started using
martensitic steels for jobs in the low-
temperature range, as a result of an
extensive research project funded by the
German federal ministry of economics
and technology. These materials are
excellent for tempering and therefore
also display higher yield strength (Rp0.2
≥ 490N/mm²) than the alternative of
austenitic steels – a property that is
particularly advantageous in such
extreme temperatures.
However, particular demands are
placed not only on the strength but also
on the toughness (KV (-196°C) ≥ 40J).
The prerequisite for high strength at low
temperatures is primarily a low content
of selected trace elements. Otherwise,
the segregations caused result in
embrittling of the casting.
“For us, the challenge lay in achieving
reliable manufacture of the castings
with a focus on optimised structure and
therefore adequate strength,” explained
Dr Petra Becker, head of research and
development. The newDux Cryomaterial
is suitable for all areas in which work is
carried out at temperatures between
-100°C and -196°C and wherever
cryogens such as dry ice or liquid oxygen
and nitrogen are used. This applies to
air liquefaction and separation systems,
in which air components are separated
using thermal separation processes to
extract nitrogen, oxygen, argon and other
noble gases in high-purity concentration.
Another application is the liquefaction
of natural gas, where the natural
gas is cooled to as low as -164°C in
LNG terminals. The demands on the
components used are high. Similar
demands apply for cold grinding and
cryogenic recycling. These processes are
used, for example, in the food industry
and in the area of composite materials.
Schmolz + Bickenbach Guss
–
Germany
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