P 713 - Production of tubes with flexible wall thickness by roll forming of strip-rolled pre-material
In today's commercially available tailored tubes, the diameter and possibly also the wall thickness vary along the longitudinal axis of the tube. This project was the first to demonstrate that the combination of strip …
Content
- Publication
- 2010
- Authors
- Prof. Dr.-Ing. P. Groche, Dipl.-Ing. M. Mirtsch, Prof. Dr.-Ing. G. Hirt
In today's commercially available tailored tubes, the diameter and possibly also the wall thickness vary along the longitudinal axis of the tube. This project was the first to demonstrate that the combination of strip profile rolling and roll forming can be used to economically produce tubes with varying wall thicknesses in the circumferential direction in a continuous process. Even as a straight tube, this makes it possible to tap into previously unrealised lightweight construction potential. In addition, it was shown that this new class of tubes can be further processed into geometrically sophisticated lightweight structures after annealing treatment, e.g. by hydroforming.
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The basis for the successful realisation of the demonstrator tubes was created through extensive simulation studies of the process chain, so that validated simulation models are now also available for the development of further profile variants. Based on a consideration of the area moment of inertia, three cross-sections for circular tubes with varying wall thicknesses were determined, which have a particularly favourable ratio of bending stiffness to weight. For the roll forming of the pipe geometry selected as a demonstrator, a 186 mm wide strip is required as the starting material, the thickness of which had to be reduced from 2.5 mm to 1.5 mm in the centre area over a width of approx. 50 mm by means of strip profile rolling. Based on the basic principles of strip profile rolling known at the beginning of the project, the influences of the process, geometry and material parameters on the formation of the cross-section were first investigated in a comprehensive parameter study with numerical simulation (FEM) and an optimised roller geometry and rolling strategy was developed. This rolling strategy was implemented on an industrial scale on a roll forming line, on which around 120 metres of Tailor Rolled Strip (TRS) were produced in three passes with a total of 25 passes for further processing. The various conceivable forming strategies for roll forming the TRS were also evaluated and optimised with the help of extensive FEM simulations. The pre-hardening from the strip profile rolling was taken into account on the basis of a measured hardness distribution and the entire moulding process was mapped as an FEM model. Based on this preliminary work, the pipes were successfully moulded and closed using HF welding, whereby the roundness and shape deviations were slightly higher than those of a reference pipe with a constant wall thickness. Bursting tests using hydroforming with free expansion showed that the tailored tubes produced in this way can be formed by hydroforming after recrystallising annealing and even exhibit slightly better formability than a reference tube in which the difference in wall thickness was produced by milling. The process combination of strip profile rolling with subsequent roll forming can be carried out on highly productive roll forming lines. This means that a high level of cost-effectiveness can be expected in particular if as few passes as possible are required to produce the TRS. This is always the case when the TRS has one or more narrow grooves. Wide or particularly deep grooves, on the other hand, are considered costly. FOSTA Research Association for Steel Application e. V.
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P 713 - Production of tubes with flexible wall thickness by roll forming of strip-rolled pre-material—
€30.00
