Refractory materials include dense shaped refractory products, lightweight and insulating bricks, fibre-based refractory products and unshaped products. They primarily have a load-bearing and insulating function. Refractory products must withstand high temperatures and corrosive media - e.g. as furnace linings in high-temperature furnaces. Depending on where they are used, they are exposed to mechanical, thermal and chemical stresses. Refractory materials used in furnace linings require a certain minimum strength and creep resistance in order not to break or creep under dead load. A high thermal or pressure fire resistance is also a prerequisite for the required dimensional stability, i.e. creep and post-sintering of the refractory materials are not permissible. The temperature cycles planned for use also require a high thermal shock resistance and resistance to thermal shock. High slagging resistance is also an important requirement for applications in which the refractory materials have direct or indirect contact with corrosive gases or melts. For insulating components, e.g. in backwalls, on the other hand, low thermal conductivities and heat capacities are crucial in order to be able to design compact and energy-efficient refractory linings.
The above-mentioned properties cannot all be realised in one refractory material and are sometimes even contradictory. High strength usually requires high relative density, but this leads to increased thermal conductivity and volume-related heat capacity. Reducing the relative density by creating additional porosity results in lower thermal conductivity, but this usually worsens the mechanical properties and abrasion resistance. Dense materials with low thermal conductivities are in turn often susceptible to thermal shock. Systematic evaluation criteria are needed to optimise properties in this conflict of objectives.
At Fraunhofer-Center HTL, refractory materials with optimised property profiles are being developed in order to find resource- and energy-efficient solutions for a wide range of refractory applications and to open up technological and economic advantages for manufacturers and end users. The refractory materials developed include acidic, basic and contact-indifferent materials made of oxide and non-oxide components as well as combinations thereof. With its test facilities and computer programmes, the HTL covers the entire manufacturing chain for the development of refractory components: from material selection and component design to backfill preparation and shaping as well as heat treatment and testing. For example, in addition to common processes such as pressing, ramming and casting, special in-house developments of the HTL are also available for shaping.
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