Moldables and refractory cement are very important for many industries. In the construction of large ovens and furnaces, where refractory linings or high-temperature firebricks are present, castable refractory cement is crucial. These are usually made up of specialized aggregate materials and thermally resistant clinker and are critical to thermodynamic stability in the heating chamber or in components that are subject to significant thermal stress.
Solids contract and expand during temperature change, especially metals, which are excellent thermal conductors. Cements which are utilized to adhere structural metals together in refractory applications need to keep their structural integrity when heat stress is present. To reduce the risk of mechanical failure during thermal expansion and contraction, refractory cement uses binding materials with enhanced thermodynamic properties. Fused minerals like alumina or aluminum oxide are employed to bind coarse aggregate materials and supply superior temperature resistant properties without compromising structure.
Refractory material is employed as the lining of ladles, furnaces, or any crucibles in the aluminum industry, where molten metal is deposited until further processing is carried out. Refractories need to withstand extremely high temperatures and shield the container from the corrosive nature of the molten metal and the flux/slag. They also help to keep the temperature that is required inside the ladle because of their thermal properties.
Due to advancements in installation techniques, aluminosilicate-based low cement castables are now used extensively in the aluminum industry for refractory linings in melting and holding furnaces, and their utilization has become more commonplace. Refractory cement has to play the triple role of protection against corrosion, providing mechanical strength, and thermal insulation when used for aluminum manufacture.
Applications in the aluminum industry can include coatings for furnace linings, trough and ladle coatings, molten aluminum splash shield protection, burners and molds, troughs, and linings for molten aluminum transfer, high-temperature patching and sealing of refractory linings, lightweight refractory linings and induction furnace coil coating.
Protection Against Corrosion
An important consideration is the durability of materials, including both ceramics and metals which are exposed to molten aluminum.
This is because molten aluminum is an aggressive metal to a number of materials. Examples of processes where this is critical are molten metal containment, die-casting, and semi-solid processing. Molten aluminum can produce considerable corrosion of the container and handling materials resulting in an unpredictable lifetime.
In the aluminum industry, refractory performance against corrosion is an important factor which affects the standard of metal created and the durability of furnace lining. Corrosion of refractory materials during the casting process for aluminum alloys increases the overall cost of production. Choosing an appropriate refractory composition for Al-casting applications takes comprehensive characterization of the physical, chemical, and mechanical properties of the materials.
This information has been sourced, reviewed and adapted from materials provided by Mid-Mountain Materials, Inc.
Source : https://www.azom.com/article.aspx?ArticleID=17072