TPT September 2007

T ube M ills: R olling & F orming M ethods

A dvances in rolling and forming processes are at once subtle and critical, like the recrystallization temperature reading which marks the boundary between cold forming and hot forming. An almost negligible difference on the thermometer has large ramifications for annealing and tempering, hardness and ductility, brittleness and cracking. Tube rolling and forming has evolved over generations of hands-on practice, and continues to develop with advances in computer numerical control (CNC) equipment. It is difficult to gauge ‘progress’ year-to-year in these closely related state-of-the-art processes.

A perhaps more useful exercise would be to note how little attrition takes place in tube rolling and forming, in comparison with basic processes in many other industries. Here, the valued methods of yesterday are not supplanted but preserved and enhanced; time-tested skills are kept up; and modifications in established procedure are always a possibility. Because tube form accuracy and repeatability are paramount, the rolling and forming archive is scrupulously maintained. Under the big tent which is our remarkable industry, nothing of real value is ever lost.

Welded tube production without marking

In many instances of tube production, marking of the tube occurs due to large speed variances between the tube and roll surfaces. Furthermore, when these variances are large, roll wear is accelerated. To overcome such problems, rolls are often designed by using rotating fi New turks head unit designed and manufactured by S+C Märker

flanges to help reduce the amount of speed mismatch. Usually, the flanges rotate on ball or roller bearings but when the rolls are small there is insufficient room to install bearings. In such cases, the flanges normally rotate ‘steel on steel’ on the centre roll journal, often resulting in wear and sticking. S+C Märker, Germany, offers a solution in order to solve these problems. The surfaces are coated with an ultra low friction solid lubrication film that provides free rotation of the roll parts. The coating process is carried out at low temperatures thus eliminating the risk of roll distortion. It has a final film thickness of 5 microns with a low co-efficient of friction of µ = 0.03. The Schmidt + Clemens Group supplies a full range of high precision roll products from its manufacturing plants S+C Bowers & Jones (UK) and S+C Märker (Germany). The complete in-house service includes extensive in-depth technical advice on rolls, plus design and development.

› Tube rolls made by S+C Märker

In addition to the manufacture of roll tooling, S+C Bowers & Jones are able to assist in a range of other areas. These include design and manufacture of roll forming lines, mill parts and equipment, design and manufacture of special purpose machines, mill refurbishment and repairs, mill upgrades and modifications, and mill and tooling inspection and status reports.

S+C Märker GmbH – Germany Fax : +49 2266 92 509 Email : rolls@schmidt-clemens.de Website : www.sc-maerker.de S+C Bowers & Jones Ltd – UK Fax : +44 1902 864 654 Email : sales@bowerjones.co.uk Website : www.bowersjones.com

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S eptember /O ctober 2007