EBNER | Products | Steel industry | Electrical steel strip | Annealing and coating line (ACL)
Heat treatment furnace facilities for the steel industry
HICON/H2 annealing and coating line (ACL).
After cold rolling, the highly worked non-grain-oriented electrical steel strip (NGO) is recrystallized in a continuous furnace and the grain size is adjusted by secondary recrystallization. A thin layer of insulating lacquer is then applied in-line with a roller coater, in order to reduce eddy current losses in the electrical motor and prevent corrosion. The process steps for this phase of production are as follows:
- Multi-stage strip cleaning
- Rapid strip heating in the heating-up section of the continuous furnace (optionally with a rapid heating system)
- Annealing for recrystallization and discontinuous grain growth in an extremely pure hydrogen atmosphere
- Controlled cooling in the slow cooling zone and final cooling zone
- Coating using a roller coater and drying equipment
The special design features of this system deliver the following advantages:
- Lowest dewpoints due to excellent furnace sealing concept and up to 100 % hydrogen process atmosphere to avoid surface oxidation, particularly for the highest-quality grades of electrical steel (> 2.5 % Si) at annealing temperatures > 1000 °C
- Homogeneous slow cooling over the width of the strip in the cooling zone, for optimum flatness → good punching and laser cutting properties in the electrical steel strip
- Material temperatures up to > 1100 °C feasible, especially with highly-efficient power plant grades such as M230-50A (> 3 % Si)
- Strip as thin as 0.18 mm can be produced for high-frequency applications
- Resource-saving and tailor-made furnace design to minimize wear part, utility and investment costs
- State-of-the-art heating system technology and rapid heating-up systems for high heating gradients to achieve improved texture (crystalline orientation)
- Process simulation before heat treatment makes it possible to identify suitable annealing programs to achieve the specified magnetic and mechanical properties
