HPH® Bell-type Annealing Furnace for Drawn Wire

The "High Performance Hydrogen®" Bell-type Annealing Plants have been developed for the heat treatment of high-quality steel wires that are used mainly for the manufacturing of complex cold extruded parts, nuts and bolts and other fastening systems. The appropriate microstructure is of essential importance for the following cold forming process of steel wires. The use of hydrogen as protective gas provides cleanest wire surfaces, a homogeneous microstructure and uniform mechanical properties. 

Due to an optimized recirculation of the protective gas, Tenova LOI Thermprocess achieves the desired uniformity of the annealing temperature within the entire charge. After the fast heating-up to the desired annealing temperature (holding time), the temperature is reduced in the metallurgically required, controlled slow cooling process. Cooling down after the heating phase is carried out with a patented jet-cooling hood. Compared with conventional cooling hoods, its cooling performance is significantly more intensive. Moreover, it requires considerably less electrical energy than a conventional cooling hood. Thanks to its low-noise operation, no particular noise-protection measures need to be taken. 

The HPH® Bell-type Annealing Plants offer a high degree of flexibility: while hydrogen is used as a protective gas for the annealing of pre-drawn or drawn wire, nitrogen is usually used for the spheroidizing annealing of wire rod. Any protective gas mixtures between 100 percent nitrogen and 100 percent hydrogen can be used since every annealing base disposes of its own separate valve stand for the protective gas supply. Consequently, annealing cycles can be implemented with that hydrogen percentage needed to meet process requirements and/or economic aspects. 

Safety is of utmost importance for working with hydrogen atmospheres: precise flow measurement, continuous pressure monitoring, oxygen probes, redundant safety technology and double solenoid valves upstream every burner are just a few equipment features. Furthermore, Tenova LOI Thermprocess is the first manufacturer using fail-safe Siemens PLC control systems. 

Tenova LOI Thermprocess focuses on robustness in the design of annealing bases: they are made of heat-resistant casting in the diffuser area and have a far longer service life than welded constructions: plant lifetimes of far more than 20 years are no exception, but quite usual. 

The high-performance impellers – a proprietary design – are specially designed for high circulation performance and low dead weight.