Caracterización de la unión vidrio-metal en la tecnología glass to metal seal y el estudio de nuevos materiales y procesos de fabricación
- Autores: Marina Sánchez Artigas
- Directores de la Tesis: José María Cabrera Marrero (dir. tes.), Josep Anton Picas Barrachina (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2021
- Idioma: español
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
This doctoral thesis has been carried out at the company VAC-TRON S.A., together with the Department of Materials Science and Engineering of Universitat Politècnica de Catalunya, in the Besós (EEBE) and Vilanova i la Geltrú (EPSEVG) campus, with the support of the Industrial Doctorate Plan of the Secretariat for Universities and Research of the Department of Business and Knowledge of the Generalitat de Catalunya.
The scientific and technological interest that justifies this research line answers the concern to know, characterize and improve the products manufactured by glass to metal seal, achieving a knowledge scientifically based that allows optimizing the current way of working in the company.
The technology of glass-metal sealing consists of the manufacture of hermetic components, composed of a metal base, a glass preform and metal pins, which are joined by heating the glass to practically a melting state, allowing it to join to metal parts. The bond generated must be hermetic and must guarantee the electrical resistivity of the glass.
Glass is the most important part of the three latter components, being responsible to generate a hermetic seal. Its main properties have been analyzed, such as: characteristic temperatures, chemical composition, particle size and microstructure. The results obtained allowed to differentiate the two most commonly used glasses, borosilicate and sodalime, relating the difference in compositions with the sealing temperature of each glass, as well as the increase in this temperature as the heating rate increases.
Once the properties of the analyzed glasses are known, the glass-metal seal has been studied according to the design of the piece and the materials used. Then the hermeticity and electrical resistance of the samples were verified and their behavior as a function of temperature and external mechanical stress were studied. The temperature cycles showed that there is no significant change in the properties of sodalime glasses, while in borosilicate glasses decreased their hermeticity after temperature cycle, when the metal body had lower thickness. On the other hand, pressure tests have shown that the height of the glass was important, breaking at the bending limit of the glass. In addition, it has been found that the critical seal is the one formed with the base. As well, thesmaller the glass diameter, the more pressure the piece resists. These results were used to perform a series of numerical simulations to obtain the rupture pressures. Some results were coincident with the simulation but others no.
Once the factors that influence the piece performance were known, new metallic materials for the bases have been studied, such as aluminum or titanium, which allow the company to enter new markets. With these new materials, it was necessary to determine the sealing curve and find the right glass to achieve the required tightness and electrical resistance. Solutions were found for both metals, although with certain limitations. In the case of titanium, the required electrical resistance was not attained by the glass, while in the aluminum case, the temperature cycles requirements were not achieved Finally, the evaluation of other alternative manufacturing methods for the metal bases was carried out. Metallic samples obtained by powder metallurgy and through the MIM and MEAM processes were studied. Because the samples manufactured by powder metallurgy and MIM were commercial ones, in which it was not possible to modify their manufacturing conditions, the results have been unfavorable, while with the samples manufactured by additive metal extrusion (MEAM), a proper seal was achieved.
