Electromagnetic stirrers are used to improve the steel quality and stabilize the productivity of continuous casters for long products. More than one thousand CONSTIR stirrers designed and manufactured by SMS Concast are successfully in operation in continuous casting plants over the world.
Electromagnetic stirring makes slag, entrapped gas and other contaminants move away from the solidifying shell of the billets, resulting in improved surface quality. In addition, stirring causes the dendrite tips to break off as the billet solidifies. This leads to the formation of new solidification nuclei and further improved billet quality. Stirring also promotes the convective heat transfer between the liquid core and the shell – another significant quality-enhancing effect.
SMS Concast designs every stirrer on the basis of its own simulations and the requirements of the customers and their specific plants. To assure that the electromagnetic stirrers achieve a maximum metallurgical effect in the liquid steel, SMS Concast has developed its own dedicated simulation program.
While building on the well-known and proven SMS Concast electromagnetic stirrer technology, the latest generation of CONSTIR stirrers comes with a series of new options that make these stirrers an ideal solution for steel producers. Apart from the stirrer units themselves, SMS Concast provides:
- Dynamic final-stirrer solutions for additional quality improvement
- Stirrer maintenance service (CONSTIR ReNew)
- CAPEX-to-OPEX solutions
Typical applications of mold, strand and final stirrers are the M-EMS mold stirrers to release entrapped slag, reduce sub-surface inclusions and reduce segregation and porosity, the S-EMS strand stirrers to expand the equiaxed zone and reduce center porosity and segregation and the F-EMS final stirrers to reduce center segregation and porosity.
Final stirrers (F-EMS) are positioned at the lower end of the solidifying billet. They improve the quality of billets – mainly of high-carbon steel billets – by reducing carbon segregation and center porosity. The stirring effect is maximized when the stirrers are positioned at an optimum position relative to the point of final solidification. The final solidification point in turn depends on many factors including section size, steel grade, casting speed and cooling intensity. Dedicated thermal simulation models, such as the COOL system developed by SMS Concast, can calculate the exact position of the final solidification point. Instead of installing the stirrer at a fixed position, the idea of dynamic F-EMS is to be able to move it to the optimal position for the specific steel grade processed and the section size cast. Several options are available to achieve a “dynamic” solution:
- Averaging FEMS: Installation of two final stirrers to average the best position.
- Movable FEMS: The final stirrer is mounted on a rail system which can be moved by hand or by a drive between two casts.
- Dynamic FEMS: A final stirrer mounted on rails is automatically moved during casting.
The best solution depends on the caster’s specific design and individual operating practices.
Under the name CONSTIR ReNEW, SMS Concast provides a broad range of services for electromagnetic stirrers. Basically every caster operator using SMS Concast stirrers can benefit from CONSTIR ReNew. The stirrers can be restored to their original specifications or even be upgraded to the specific requirements of the customer. Depending on the condition of the stirrer and the production requirements, the CONSTIR-EMS ReNew services may include:
- Electrical testing and evaluation
- Mechanical repair of physical damage
- Preventive epoxy re-impregnation
- Full rewinding and repair
SMS Concast offers this service out of Europe, and since 2019 also out of North America.
SMS Concast provides customized solutions that enable the conversion of capital expenditure into operating expenditure. It is possible, for example, to lease the CONSTIR-EMS units on performance-based payment or monthly remuneration schemes. In this context, SMS Concast also provides integrated stirrer condition monitoring options.