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HFI welding

HFI welding

Mannesmann Line Pipe uses the high-frequency induction (HFI) resistance pressure welding technique for longitudinal welding. The endless strip passes through rolling stands where it is shaped to an open pipe, which runs through a high-frequency inductor consisting of a metal coil with single or multiple windings. As a result, high-frequency ring current is induced into the pipe that closes preferably at the strip edges which converge in the welding point. The temperature required for welding is generated by resistance heating of a narrow zone along the strip edges.

The heated strip edges are squeezed together by pressure rollers, resulting in a homogeneous longitudinal weld without any filler metals. The flash generated on the inside and outside surfaces during welding is scraped off to the level of the pipe surface with special tools.

Immediately afterwards, the HFI weld is subjected to a multi-step inductive annealing treatment to ensure that the properties in the weld area match those of the base material. Then the continuous pipe string is straightened, size rolled and finally cut to length by a flying saw.


Knowledge floater

In cooperation with Bergische Universität Wuppertal we have produced a knowledge floater on the subject of HFI-welded steel pipe. In a straightforward, easily understandable style, it serves as an introduction to longitudinal welding using the high-frequency induction process. The focus is on the actual welding process, with a brief digression on weld annealing. As a finishing touch, the floater presents an overview of our products and their applications.

A knowledge floater is a brief educational video that uses numerous auditory and visual elements to provide a concise and interesting outline of a small and self-contained area of knowledge. As a special feature, the instructional texts are also spoken. The resultant audiovisual learning effect turns the presentation into a true multi-sensory learning experience. The floaters can be downloaded free of charge by anyone interested. Pupils and students thus gain an insight into engineering know-how, the manufacture of technical products and their impact on everyday life as well as into the underlying scientific theory. For teachers at schools and universities, podcast science floaters are a useful and stimulating instructional tool.


Contacts

Animation of HFI welding
Flash animation HFI welding
Production steps in the welding mill
Production steps in the welding mill
© Mannesmann Line Pipe GmbH
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