TPT 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.

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Formtek, Inc – USA Fax: +1 216 831 7948

Messe Düsseldorf GmbH Postfach 101006 _ 40001 Düsseldorf _ Germany Tel. +49(0)211/4560-01_Fax +49(0)211/4560-668 www.messe-duesseldorf.de

Email: yoder@formtekgroup.com Website: www.formtekgroup.com

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M arch 2013

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14.02.13 08:30