In a joint research project with the AIT Austrian Institute of Technology, the Plansee Group, headquartered in Reutte, Austria, is working on reducing energy consumption in its production processes.
To achieve maximum performance, many products must undergo lengthy and energy-intensive heat treatment such as an annealing process. One of the ways of annealing these items is to use electrically-heated high-temperature furnaces with zone temperature regulation, in which the products are arranged in layers.
THE WORLD OF POWDER METALLURGY TO YOUR INBOX
Subscribe to our weekly newsletter
The inside of the furnace heats up until the specified zone temperature is reached. This temperature is then maintained for a certain length of time to guarantee that the products are heated to the specified temperature and are annealed for a minimum time at this temperature. The products are then cooled down again.
In practice, precise adherence to this minimum annealing time is important, as the temperature progression in the products is heavily dependent on the load of the furnace and the temperature progression does not follow the zone temperature exactly due to thermal inertia of the materials. It is also extremely difficult to measure the temperature (up to 1800ºC) of the heat-treated objects directly: suitable load thermocouples are expensive, delicate, and difficult to install, while the software models for temperature estimation are very complex. For this reason, in practice there is a tendency to exercise caution and opt for a longer annealing process. If this is too short, the annealing material is not annealed homogenously for long enough, which has a negative effect on the material properties. If it is too long, time and energy are wasted.
To optimise the annealing process, Plansee has launched the ThermoTec project together with the AIT Austrian Institute of Technology. “In this project, we have combined Plansee’s expertise in materials and processes with our knowledge of regulating difficult and complex processes,” stated Martin Niederer, AIT project manager.
Through complex measurements, analyses, and modelling, an algorithm has now been developed. Experimental validation of the algorithm in more than 230 annealing operations on a furnace over the course of a year revealed that the holding time of the process could be reduced by 20%, on average. The reduction in energy consumption and CO2 emissions is equivalent to that of fifteen homes.
Accompanying material tests showed that the product quality remained unchanged at a high level. Optimisation also reduced the total duration of the process by almost 12%, which enables better utilisation of the furnace.
“The process ensures precise adherence to the minimum annealing time, which results in energy savings and thus heating costs, as well as improved throughput with consistently high quality,” stated Tobias Glück, head of the Competence Unit Complex Dynamical Systems.
The process is now being used in production operations at Plansee and is contributing toward reducing the energy demands of the production department.
Bernhard Mayr-Schmölzer, project manager at Plansee, concluded, “The new algorithm can be integrated into the existing furnace control and can therefore be transferred to other furnaces with ease. We will continue to roll this out over the coming months.”