DON’T SPOIL THE COIL!
Significantly less laminar imperfections thanks to CENTRICORE 4.
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CENTRICORE is a group of materials used to make spools in a centrifugal casting process.
Spools, also known as winding spools or occasionally rolling mill sleeves, are thick-walled tubes used for winding thin aluminium
strips, aluminium foil or stainless steel thin sheet metal for transportation in the manufacturing process and storage. The wound
metal is called a coil.
If the coil requires thermal treatment in an oven prior to the next rolling or winding process, the spool has to withstand
enormous mechanical and thermal stress. Otherwise permanent distortions may occur that would affect every consequent
coiling process with that spool.
When CENTRICORE 4 was developed for spools for winding thin aluminium strips and
aluminium foil in the 1980s, it was necessary to find out the stress levels they would need to withstand from the belt tension
and coil weight on the one hand, and from the 24-hour oven heat of around 480° C, on the other.
The St-52 or nodular cast iron (GGG) spools in use up to then were problematic, with many cases of permanent deformation,
causing damage to the coils within a short time on account of the high mechanical and thermal stresses. It was not uncommon
for the middle part of a spool to contract after just a few months because the materials used were unable to withstand the
thermal expansion of the wound metal. As a result, the beginning of every wound metal coil would crease and overlap, making
it unfit for use.
In some cases, up to eight per cent of a coil was then reject material, and the deformations had to be mechanically corrected
at considerate expense. For this reason, the former spools were made with very thick walls to ensure sufficient stability
after repeated mechanical reworking.
CENTRICORE 4 was developed and optimised in a series of complex tests.
It is a Cr-Mo-V (chromium molybdenum vanadium) alloy steel that is manufactured in a centrifugal casting process.
A special chemical analysis with ensuing thermal treatment guarantees the necessary mechanical properties.
The spool geometry was computed with a customised application to achieve optimal wall thickness. The inner diameter
was not changed so as to emulate the existing technical circumstances of the winding and rolling equipment.
In the final manufacturing stage, each CENTRICORE 4 spool is processed entirely mechanically according to supplied
drawings, checked for internal and external imperfections, and the unbalance is measured dynamically. This is the
only way to ensure the high quality and long life cycle of our spools - for the multiple benefit of our customers:
creases and overlaps of the thin aluminium strips, aluminium foil or the stainless steel thin sheet metal are reduced
to less than one percent, cost-intensive repairs of major spool deformations are now a thing of the past.
Small wonder, then, that more than 7,000 CENTRICORE 4 spools are in everyday use across the entire world.