In industrial steel processing, box furnaces with slot openings are gaining increasing attention. This concept, implemented among others by NUTEC Bickley, is used for the thermal preheating of steel components prior to downstream processes such as forging, forming, or bending.
The systems are gas-fired batch furnaces designed for operating temperatures of up to 1,300 °C. A defining feature is the narrow, slot-shaped opening through which the material is charged into the furnace. This design enables a compact layout while reducing direct heat exchange with the surrounding environment.
To thermally shield the opening, an air curtain system is employed. It separates the hot furnace interior from ambient air and helps limit heat losses as well as uncontrolled air ingress. The system is complemented by fans for controlled combustion air supply and for exhaust gas removal.
Burner and Control Technology
Heating is provided by high-performance burners operated via proportional control systems. Key parameters such as temperature, pressure, and the air-to-gas ratio are continuously monitored and adjusted. In furnaces with multiple heating zones, different temperature profiles can be implemented, supporting uniform heating of the charge.
For operational safety, automatic shutdown mechanisms are integrated. If a defined maximum temperature is exceeded or a burner failure occurs, the system automatically interrupts the gas supply. Flame monitoring is carried out using UV sensors, which, in combination with safety relays and alarm signals, ensure reliable operation.
Thermal Insulation and Energy Efficiency
A key element of the furnace design is the multi-layer thermal insulation system. The furnace floor is typically made of cast refractory materials, while the side walls and roof are lined with high-density ceramic fiber modules. This combination reduces heat losses, improves energy efficiency, and keeps the external temperature of the steel casing within safe limits.
Additional inspection ports allow operators to visually monitor the heating process without interrupting operation, supporting stable and controlled process management.
Integration into Industrial Applications
The slot-type box furnaces implemented by Nabertherm illustrate how design adaptations, modern control technology, and optimized insulation concepts can be used to update conventional furnace systems to meet current industrial requirements. The technological approach focuses less on maximum throughput and more on controlled heating, process reliability, and reproducible temperature profiles.
