Simulation and Testing of a Modified Mould on UGITECH’s ESRR

Since the end of 2007, UGITECH S.A. has been equipped with an ESRR™ plant provided by INTECO Special Melting Technologies GmbH. This technology uses a superheated slag to remelt electrodes, in a T-shaped mould equipped with an upper graphite current collector: the current is split into two separate paths. This feature makes the ESRR™ process specifically appropriate to remelt a main electrode into smaller products like billets, with a rather high productivity. Nevertheless, the unique need of UGITECH S.A. to remelt continuous casting blooms, while keeping their 205 × 205 mm section constant, implies quite a small section electrode compared to the normal ESRR™ practice. The initial mould configuration of the machine had to be modified to take better into account this specific demand. The ESRR™ plant is a complex process which combines many simultaneous phenomena—electromagnetic, heat transfer, fluid flow, etc.—with a strong coupling. The first numerical model of this process was built, and data taken from literature [2-15] helped to develop its first heat transfer simulation. Despite the necessary simplifications and work hypotheses, this approach has given these first important results: to confirm the presence of organized toroïdal motions in the slag, to provide orders of magnitude for variables one cannot measure in situ (slag flow velocity, temperature distribution), and to compare the ESRR™ mould in its original configuration with a new design. Several industrial trials, performed in the target configuration and simulated with a modified current upper collector, have demonstrated obvious improvements both on the surface quality of the ingots (directly related to the temperature at the metal meniscus) and on the stability of the machine’s regulation (melting speed and electrode immersion). After this confirmation of the advantages of the new configuration, UGITECH S.A. finally placed an order to INTECO GmbH for a new design mould and an associated body.