Fluencia en materiales refractarios

Los materiales refractarios son ampliamente utilizados en diversos sectores industriales en virtud de sus excelentes propiedades y desempeño en ambientes agresivos. Sin embargo, a pesar de que la resistencia a la deformación por fluencia es una de las propiedades más importantes para la selección de esta clase de materiales, son pocos los trabajos abocados al entendimiento de los principios básicos y tecnológicos de su rendimiento a altas temperaturas. En este contexto, este trabajo aborda: 1) los mecanismos de fluencia, 2) los modelos matemáticos propuestos para el análisis y previsión de la deformación por fluencia a alta temperatura, 3) procedimientos técnicos y ensayos experimentales y 4) un análisis crítico de algunos aspectos básicos y prácticos, considerando la literatura disponible sobre el tema. A partir de la información recolectada, se considera que los modelos matemáticos (como el concepto de Proyección θ) constituyen una poderosa herramienta para la previsión del comportamiento a la fluencia de los refractarios, ayudando en la identificación de los principales mecanismos de fluencia de estos materiales e induciendo al desarrollo de composiciones optimizadas para atender las necesidades de sus usuarios finales.Refractory materials are widely used in various industrial fields due to their outstanding properties and performance in aggressive environments. However, although creep resistance is one of the most important properties for the selection of these materials, few researches were carried out focused on the fundamentals and technological understanding of their performance at high temperatures. In this context, this work addresses: 1) the creep mechanisms, 2) the mathematical models proposed for the analysis and to forecast the creep deformation at high temperature, 3) technical procedures and experimental testing, and 4) a critical analysis of some basic and practical aspects considering the literature available on this issue. Based on the collected information, mathematical models (such as the Projection θ concept) were considered as a powerful tool for the prediction of the refractories’ creep behavior, helping to identify the main creep mechanisms in these materials and to induce the development of optimized compositions able to attend the end-users requirements.Fil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina;Fil: Luz, A. P.. Universidade Federal de São Carlos. Departamento de Engenharia de Materiais; Brasil;Fil: Pandolfelli, V. C.. Universidade Federal de São Carlos. Departamento de Engenharia de Materiais; Brasil

Caracterizacion de cuerpos en verde precursores de materiales porosos de cordierita conformados por consolidacion termica de almidones nativos

En este trabajo se presenta una parte de los resultados obtenidos en el marco de un proyecto de cooperación internacional en el que se estudian materiales porosos a base de cordierita obtenidos por consoli-dación térmica de suspensiones cerámicas con diferentes almidones nativos, en particular, aquéllos relacionados a la caracterización de los compactos en verde. Para la obtención del material de cordierita se partió de una mezcla precursora de caolín, talco y alúmina, y como agente consolidante/ligante y formador de poros a alta temperatura se emplean: almidones nativos de papa, maíz o tapioca. La caracteriza-ción de los materiales en verde se llevó a cabo por medidas de densi-dad y porosidad, análisis microestructural y evaluación del comporta-miento mecánico. En base a la información obtenida, se concluyó que el almidón con mejor comportamiento global es el de papa.Fil: Lambertini, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Sandoval, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Talou, Mariano Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Camerucci, Maria Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Gregorová, E.. Institute of Chemical Technology; República ChecaFil: Pabst, W.. Institute of Chemical Technology; República Chec

Experimental procedure for the mechanical evaluation of oxide-carbon refractories by strain measurement

Experimental issues regarding the implementation of a methodology for obtaining strain-stress curves at high temperatures and in a controlled atmosphere of oxide-C refractories are presented. These curves give a detailed description of the material’s mechanical behavior that is not attainable using conventional tests. The method to measure the specimen strain by contact extensometry and the system to control the atmosphere by a gas flow are described. As an example, the experimental study of commercial Al2O3-MgO-C refractory bricks used in steel ladles at high temperature (1260 °C) in both air and N2 atmospheres is presented showing the valuable information obtained applying strain-stress measurements.Fil: Muñoz, Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Rohr, A. L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Cavalieri, Ana Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin

Thermodynamic simulation models for predicting Al2O3-MgO castable chemical corrosion

The chemical corrosion of two Al2O3–MgO castables (containing distinct binder sources: hydratable alumina or calcium aluminate cement) were evaluated in this work via thermodynamic calculations. Two simulation models were proposed according to the following procedures: (1) firstly the matrix and later the aggregates of the castables were placed, separately, in contact with an industrial basic slag, and (2) the overall chemical composition of the design castables was directly reacted with the molten slag. The theoretical results were further compared with experimental data collected after corrosion cup tests. Although the thermodynamic evaluation of the overall castable compositions was able to identify the phase transformations correctly, a two-step analysis of the matrix components and aggregates particles seems to be the best alternative to evaluate the binder source effect on the corrosion performance of the two Al2O3–MgO refractory materials.Fil: Luz, A. P.. Federal University of Sao Carlos; BrasilFil: Braulio, M. A. L. . Federal University of Sao Carlos; BrasilFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Pandolfelli, V. C. . Federal University of Sao Carlos; Brasi

Thermodynamic evaluation of spinel containing refractory castables corrosion by an industrial secondary metallurgy slag

This work addresses the thermodynamic evaluation of different spinel-containing refractory castable compositions in contact with a basic steel ladle slag (CaO/SiO2 ~ 9). The main differences among the castable compositions were the amount of silica fume (0 or 1 wt%), the binder source (calcium aluminate cement or hydratable alumina) and the spinel incorporation route (in situ or pre-formed). The interaction of the liquid slag with the refractory was carried out with the help of thermodynamic software (FactSage) and the applied methodology considered the changes in the slag composition due to the interaction with the castable. The theoretical results were compared with the experimental data attained by corrosion cup-tests, pointing out that the thermodynamic calculations were suitable for predicting various aspects observed in the corroded samples by SEM. Therefore, the equilibrium simulations led to parameters that indicated the corrosion resistance trends, complementing the experimental evaluation and reducing further experimental testing.Fil: Luz, A. P.. Federal University of Sao Carlos; BrasilFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Braulio, M. A. L.. Federal University of Sao Carlos; BrasilFil: Pandolfelli, V. C.. Federal University of Sao Carlos; Brasi

Al2O3-based binders for corrosion resistance optimization of Al2O3-MgAl2O4 and Al2O3-MgO refractory castables

Abstract This work addresses the main aspects related to the use of alternative binders [hydratable (HA) or colloidal alumina (ColAlu)] in castables containing different spinel sources (pre-formed or in situ generated), in order to point out: (i) the features that control the corrosion behavior of these materials, and (ii) the key factors to better select a refractory composition. Thermodynamic calculations, corrosion cup-test and SEM analyses were carried out in order to evaluate the slag attack of the designed refractory compositions. According to the attained results, the alumina-based binders (HA or ColAlu) induced a more effective sintering process due to their high specific surface area, improving the physical properties and the binding level of the generated microstructure. The spinel grain size also played an important role in the corrosion behavior of these refractories, as the finer the particles, the greater their dissolution was into the molten liquid, leading to further precipitation of spinel in the solid-liquid interface as a continuous and thick layer. Among the evaluated compositions and considering the presence of silica fume, the most suitable formulation with optimized corrosion resistance was the one with in situ spinel generation and HA as a binder.Fil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Luz, A. P.. Universidade Federal do São Carlos; BrasilFil: Braulio, M. A. L.. Universidade Federal do São Carlos; BrasilFil: Pandolfelli, V. C.. Universidade Federal do São Carlos; Brasi

Slag attack evaluation of in situ spinel-containing refractory castables via experimental tests and thermodynamic simulations

Although the in situ spinel formation in alumina–magnesia refractory castables induces an expansive behavior, many investigations highlight its positive role in the corrosion resistance of such materials. Thus, this work addresses the slag attack evaluation of four designed in situ spinel-containing castables (containing hydratable alumina or calcium aluminate cement as a binder source and 0 or 1 wt% of silica fume) when in contact with a FexO rich industrial slag. Corrosion cup-tests, microstructural characterization and a two-step thermodynamic simulation model were used in order to investigate the reactions taking place during the slag–refractory interactions. According to the attained results, hydratable alumina seems to be a suitable binder to improve the corrosion resistance of such castables, as it induces densification and the formation of an alumina-rich spinel phase at the slag–matrix interface. Moreover, the thermodynamic calculations matched to the experimental observations, attesting the efficiency of the proposed simulation model for the evaluation of the in situ spinel-containing castable corrosion behavior.Fil: Luz, A. P.. Universidade Federal do São Carlos; BrasilFil: Braulio, M. A. L.. Universidade Federal do São Carlos; BrasilFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Pandolfelli, V. C.. Universidade Federal do São Carlos; Brasi

Creep behavior modeling of silica fume containing Al2O3–MgO refractory castables

Alumina–magnesia refractory castables usually present silica fume in their compositions, due to their ability to induce better flowability and to compensate the expansion related to the in situ spinel formation. In this paper, four compositions containing distinct silica fume content (0–1 wt%) were designed and analyzed by creep resistance and hot mechanical strength. The u-projection concept coupled with the thermodynamic simulations were used in order to predict the creep behavior and to identify the main mechanism leading to the deformation of the samples. Based on the collected results, a linear correlation between the creep parameters (ui) and the silica fume content was attained by analyzing the experimental data, resulting in reliable data and the likelihood to simulate the performance of other compositions in the same system. Moreover, particle sliding assisted by viscous flow was suggested as the dominant creep mechanism in the studied castables.Fil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Luz, A. P.. Federal University of Sao Carlos; BrasilFil: Braulio, M. A. L.. Federal University of Sao Carlos; BrasilFil: Pandolfelli, V. C.. Federal University of Sao Carlos; Brasi

Basic slag attack of spinel-containing refractory castables

The better performance of spinel-containing refractory castables when in contact with basic slag is mainly associated with their higher corrosion resistance. Although the literature has shown various studies related to this subject, only few of them evaluated the overall microstructural effect on the corrosion resistance. Considering this aspect, four different compositions were produced, in order to evaluate the binder source influence (calcium aluminate cement or hydratable alumina), the silica fume addition and spinel incorporation method (in situ or pre-formed) effects. Based on the physical properties (apparent porosity, linear thermal expansion and pore size diameter distribution) and also on the phases generated (detected by SEM, before and after corrosion), a basic slag corrosion mechanism, for the set conditions, is proposed. The results pointed out that lower penetration can be attained by reducing the pore size diameters, whereas chemical corrosion resistance is a consequence of higher content of fine alumina, lower amount of calcium aluminates and the lack of liquid phase in the castable matrix. This study stresses that the castable formulation design and the proper raw material selection are of utmost importance to understand and master the performance of this class of refractory castables.Fil: Braulio, M. A. L.. Federal University of Sao Carlos; BrasilFil: Tomba Martinez, Analia Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Luz, A. P.. Federal University of Sao Carlos; BrasilFil: Liebske, C.. Ceramics Research Centre; Países BajosFil: Pandolfelli, V. C.. Federal University of Sao Carlos; Brasi