Etude des verres et vitrocerames cordieritiques pour applications dans l'industrie de l'aluminium.

摘要

The primary aluminum industry faces, since the emergence of industrial production processes, problems related to corrosion of the refractories used as confinement materials for molten metal. Refractories are used in parts of the plant where melting and handling of liquid metal occur (melting furnaces, transfer launders, etc.). Indeed, the castables and the technical ceramics employed in the industry of primary aluminum are vulnerable to molten metal. This deficiency causes in addition to their premature deterioration, the contamination of the metal produced. It became then imperative (a must), to solve this problem, either by improving the chemical and mineralogical composition of the materials or by developing new and more resistant materials.; The primary objective of our research is to develop a solution (new material or additive), capable of eliminating or at least reducing the corrosion of conventional materials by molten aluminum alloys. At the same time, the solution should fulfill the application requirements related to mechanical and thermomechanical properties. This implies: low porosity and high chemical stability as well as superior mechanical strength and thermal shock resistance.; The physical and chemical properties of cordierite based glass ceramics, qualify them as ideal candidate for applications such as transfer launders. However, there has been up to now no application of these materials in aggressive conditions, such as in molten metal transfer launders.; In the context of this thesis, we issued some hypothesis, concerning the possibility of using cordierite based glass ceramics (as monolithic object or as additive in standard castables), in the primary aluminum industry. We postulated that cordierite based glass ceramics possess the required properties for implementation in the industry, which are: the corrosion resistance, the mechanical strength and the thermal shock resistance.; After developing the process of producing our cordierite based glass and glass ceramics, we successfully validated the first hypothesis. Indeed, the corrosion resistance of our materials to molten Al-5% Mg, is by far better than any of the commonly used materials in the industry. The mechanical strength related hypothesis was validated for the monolithic variant of our material. The latter showed clearly better properties compared to common silica based castables. For the variant as additive in an aluminosilicate castable, the mechanical properties were less probative. However, we noted an increase in term of mechanical strength. Concerning thermal shock resistance, we discovered that our material was almost unaffected. Moreover, compared to commonly used silica based castables, thermal shock resistance was by far higher.; After validating all of our starting hypothesis, the study confirmed that our cordierite based glass ceramics can without any doubt, substitute silica based castables and certain components of aluminosilicate castables. These castables are beeing used respectively as building material for transfer launders and melting furnaces. (Abstract shortened by UMI.)