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82 March 2013
Stainless steel production
Reshaping
stainless steel
tubing
MANY producers of round austenitic stainless steel tubing
wonder how much reshaping can be performed while not
harming the material integrity due to cold working, and how to
orientate that section for their mill system.
Taking round product and reshaping, or reforming, into
complex shapes is common among carbon steel tube producers
but not common to austenitic stainless steel producers. The
term “complex shape” does not necessarily require various
sharp angles, which have no purpose in fluid or heat transfer
applications. Instead, complexity can encompass very thin,
tall elliptical shapes that are not easily produced on standard
reshaping-capable tube mills.
Depending on the application, five, six, seven or more stands
are required to reshape round product into elliptical shapes. It
essentially depends on how much material must be physically
moved. A well-engineered tooling arrangement will design
around a specific amount of material movement that can be
accomplished per pass, per horizontal centre (centre between
driven stands), etc.
Unlike more common tubing applications, the manufacture
of complex stainless steel tubing requires an integrated tooling
and mill design to optimise the forming process. Most tube mill
system producers do not have this expertise in-house and must
work with their tooling suppliers externally to determine the
correct material flow patterns that yield satisfactory results.
As part of the Formtek Group, Yoder Manufacturing is able
to supply tube mills, roll tooling and cut-off equipment, in
conjunction with Hill Engineering, another Formtek company.
As a whole, they are able to look at the complete manufacturing
system and apply appropriate disciplines to yield a system that
reshapes round, fusion welded tubing into an ellipse. Based
on recent installations, Yoder installed an elliptical tube system
that produces a finished product that is 73 per cent thinner
than the incoming round tube diameter.
Due to the reshaping tooling designs, the final product had
minimal surface marking, typically caused by speed mismatch,
which was accomplished by considering the profile orientation
through the mill: the tall axis of the ellipse is horizontal, taking
advantage of the natural forming state of the driven stands,
while reducing the effects of rotational speed differences, due
to changes in tool-to-section radii.
Orientating a section like this would normally cause
problems for cut-off manufacturers because the system
requires a horizontal flow to shear the ellipse to length. Yoder
and Hill Engineering were able to determine that designing a
cut-off with a complete horizontal cutting motion yielded more
advantage to the reshaping process.
Reshaping of austenitic tubing is possible, but the overall
manufacturing solution with forming, tooling and cut-off as an
integrated system must be considered.
Formtek, Inc – USA
Fax: +1 216 831 7948
Email:
Website:
Messe Düsseldorf GmbH
Postfach 101006 _ 40001 Düsseldorf _ Germany
Tel. +49(0)211/4560-01_Fax +49(0)211/4560-668
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