New measuring method registers the position of glowing steel rings

forging
New measuring method registers the position of glowing steel rings



By Mirko Gröper, David Bailly and Gerhard Hirt

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Ring rolling creates parts that are indispensable in many industries. In order to be able to map an even wider range of products, researchers from Aachen have developed a new measurement method.

Rolling of a red-hot steel ring on a Banning H100/V80 radial-axial ring rolling mill at the Institute for Metal Forming in Aachen. Now the position of such items can be precisely recorded. Find out how it works here.

(Image: Ahrens + Steinbach Projects)

Ring rolling is a well-established and economically solid forming process for the production of large seamless rings, which are used, among other things, as safety-relevant components in the energy, automotive and aviation sectors. [1]. Typical applications are roller bearings or connecting flanges for wind turbines [2]. Also components for aircraft turbines [3] belongs to. In addition to the long life and good mechanical properties of ring-rolled products, the process is characterized by a very high material efficiency, especially when non-rectangular, almost net-shaped cross-sections are produced with it. [4].

Rolling targets are not trivial

In recent years, options have been developed to make the process more flexible by expanding the product range of conventional radial-axial ring rolling mills, for example in the production of profiled steel rings. Among other things, approaches were chosen that supplement the conventional system technology with measurement and control concepts. However, due to the complexity of the ring rolling process, this process places high demands on operational measurement technology. In hot solid forming, the harsh conditions such as steam, dust, vibrations, external light sources and the high degree of ring coverage of the tools stress the metrological systems. In addition, the high temperatures of over 1,000 °C that normally prevail during hot forging can significantly degrade the accuracy of the measuring technology and even damage it in the long term.

The location of the track ring despite harsh conditions

As part of an ongoing DFG project, the Institute for Metal Forming (IBF) requires ring rolling of close-to-net eccentric rings with a circumferentially variable wall thickness. To achieve this, the ring position or the current wall thickness in the roll gaps must be precisely tracked, because the opening and closing of the radial roll gap (dynamic adjustment of the mandrel roll) must be controlled based on these variables. Therefore, a new idea was pursued, which, despite the harsh conditions, can track the rotation of the ring and, based on it, its position.

The choice fell on measuring the peripheral velocities of the centering rollers because it can be measured independently of the forming zones. This avoids a possible falsification of the measurement. Basically, with this knowledge, the peripheral velocities of the ring can be determined. By incrementally summing up the individual time intervals, the distance traveled around the perimeter can then be calculated. The distance can be adjusted in relation to the ring’s prevailing material thickness. Finally, the position of the ring in the ring rolling mill can be determined. In addition, with the expansion of the measuring technology at the ring rolling mill, additional support points can be created, with which additional data about the condition of the ring during the rolling process can be collected. This data can be used to perform an extended comparison of the real ring position for simulating the process. With this knowledge, new rolling strategies can then be developed in a simulative way.

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