EBNER HICON/H₂ annealing and coating line (ACL)

HICON/H₂ annealing and coating line (ACL).

After cold rolling, the highly worked non-grain-oriented electrical steel strip (NGO) is recrystallized in a horizontal 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 rapid heating systems up to 500 K/s)
• Option: decarburization to prevent magnetic aging
• Annealing for recrystallization and discontinuous grain growth in process atmosphere
• Controlled cooling in the slow cooling zone and final cooling zone
• Coating by roller coater and drying in a floater furnace

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
• The very latest burner/radiant tube technology and rapid heating-up systems for high heating gradients to achieve efficient decarburization and 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
• Hydrogen regeneration units, which provide hydrogen savings of up to 50 %, are available