HITT high-temperature bell annealer facility for electrical steel strip (HBAF).
High-temperature anneals (HTA) of grain-oriented (GO) electrical strip are used to form grains with magnetically advantageous Goss textures through secondary recrystallization. The high processing temperatures (above 1150 °C) and straight hydrogen atmospheres also remove sulfur and nitrogen. A coating of MgO, added in a previous step, inhibits the formation of stickers in the wraps.
The safety concept for processing in hydrogen has been adopted from HICON/H2 annealers. The charge is heated by thermal energy radiating from the heating bell and inner cover.
The following advantages over other facility types are provided by the EBNER design:
- Encapsulated, gas-tight workload space ensures significantly lower atmosphere consumption (savings of up to 50 %), compared to alternative designs
- Rapid heating up and cooling, with possible hydrogen concentrations up to 100 % → significant increase in productivity compared to 100 % nitrogen atmospheres
- Further reductions in hydrogen consumption are possible if a hydrogen recycling system is installed
- The homogenous temperature distribution within a stack, provided by patented coil supports and symmetrical heating, ensures:
- homogenous magnetic characteristics
- shortened annealing cycles
- and extends the service life of the inner covers
Technical data of the workload space:
- Diameter: 2200 mm
- Charging height: 3000 mm
- Max. weight of charge: 36 t
- Heating system: gas-fired, electric heated