Nowadays rheology is quite commonly known and established in various industries. The same applies for rheology measurements at temperatures up to 1750 °C: The glass or metal industries are increasingly discovering the advantages that rheological characterization of their materials can have for their businesses. This article lists the benefits of high temperature rheology.
High temperature rheology
Reduced energy costs
Process industries, for example the metal or glass industries, require a high amount of energy. Therefore, a big portion of their annual turnover has to be spent on energy. However, increasing energy costs and governmental regulations force companies to actively pursue a reduction of their energy consumption. In order to do so they decide to invest into either closed-loop and heat recuperation systems or new production equipment that works more efficiently. Although these options work more efficiently with the energy provided and are more economical in the long run, they require big investments at first. Rheology offers a cheaper alternative. By investigating and understanding the rheological behavior of the processed material around the typical processing temperature, companies can start to experiment with lowering the maximum process temperatures. For most applications the viscosity of the molten material needs to be within a certain range to guarantee a good processibility of the material and a satisfying quality of the product. But if this range of viscosity is already achieved at lower temperatures, substantial amounts of energy can be saved which in return can be converted into financial savings.
Rheology supports enamel production plants in meeting their quality and productivity targets.
Reduced scrap rate
Defect products consume the same amount of resources during their production as saleable products but do not contribute to the turnover of a company. In many cases defective products have to be dumped, reprocessed, or fed back into the manufacturing process as raw material. The reasons why some companies have a high scrap rate can be manifold, but in most cases the reason is a poorly understood or adjusted manufacturing process. Rheology helps investigate the processed material beforehand under realistic conditions, simulate the following manufacturing process, and thereby gather important information for the adjustment of the manufacturing process. This helps turn down scrap rates, make better use of natural and financial resources, and improve time management in production.
Increased efficiency in R&D
Research and development is, of course, also important in established industries such as the metal and glass industries. New chemical compositions of glass, for instance, help supply more and more new applications and broaden the range of fields in which glass is applicable. Also metal producers try to increase their market size by investigating new alloy compositions with unique characteristics for new applications. Understanding the rheological behavior of the processed material is crucial here, as glass and metal are in a molten and liquid state at least in one step during their production process. Here rheology can provide indications about the flow and filling properties of new alloys or about their softening and hardening behavior. Also changes in the materials’ chemical composition during processing at high temperatures and the resulting impact on the manufacturing process and the final product can be investigated. This helps find the best material combination to meet the set specifications and the increasingly complex demands of customers.
Steelworks increasingly consider rheological investigations of their melts to further improve their production processes.
Improved quality control
Another application of rheology is incoming goods inspection and raw material characterization. Customers in the flat glass and container glass industries, for example, characterize their raw material at certain intervals to make sure that the material will behave as expected in the manufacturing process and the composition of the raw material complies with the defined specifications. If changes in the raw material composition are detected, the company gets the possibility to either complain to the suppliers about the quality of the purchased raw material or to adjust process parameters accordingly. High temperature rheology supports the quality control system.
Increased process efficiency
The heart of a company active in the process industry is the production process itself. Companies depend on a well-adjusted and optimized production process in order to be financially successful. Especially the production steps in which the raw material is molten and further processed in its liquid state are critical and require the most attention. One of the most commonly known indicators for the performance of a manufacturing process is the overall equipment effectiveness (OEE). This indicator combines the availability and the performance or productivity of, for example, a glass manufacturing process with the quality of the produced parts. A high OEE requires a good performance on all three dimensions: availability, productivity, and quality. This can only be achieved if the processed material is thoroughly analyzed under process conditions, where, again, rheology is required.
Increased product quality
An improved process and fully understood behavior of the sample material inevitably lead to a better product quality. For example, a huge problem in the casting industry is the shrinkage of the casted material during cooling. This process causes failures in the final product which either results in flawed parts that cannot be used or an inferior quality of the final product. The lower the temperature of the molten metal is in the moment when it is poured into the molds the smaller is the thermal shrinkage during cooling. Rheology helps foundries identify the lowest possible process temperature at which the material still flows satisfactorily enough to fully fill every corner of the mold in order to avoid shrinkage.
In glass production knowledge about the viscosity of the molten glass highly influences the quality of the products.
Reduced maintenance costs
Maintenance of plants in the process industry makes up a big part of the total running costs. Companies therefore put a lot of effort into maintenance programs and try to find solutions for decreasing the wear of their systems in order to increase their life span. Here viscosity plays a crucial role. In steel manufacturing processes, for example, the refractory material inside the furnace is worn at the interface with the molten pig iron. A lower viscosity of the sample results in a faster wearing of the refractory material. By characterizing the molten material in the laboratory beforehand, companies can decide on how to alter the viscosity of their material – either by adding additives or by settling for a different refractory material altogether.
Conclusion
Rheology at temperatures up to 1750 °C can be highly beneficial when it comes to keeping production costs at a minimum. For this, rheological know-how but also a deep understanding of the chemical reactions and material-internal processes at high temperatures are necessary to fully benefit from the possibilities offered by devices like the Furnace Rheometer System by Anton Paar. The rate at which these kinds of systems are adopted is increasing rapidly and customers who characterize their material with rheology benefit from a knowledge-gain and generate competitive advantages.