THERMOSTRUCTURAL BEHAVIOR OF A REFRACTORY CONCRETE FOR LADLE FURNACE

• DOI: 10.37572/EdArt_1012257581

• Palavras-chave: Alumina; Spinel; Refractory; Dilatometry; XRD.

• Keywords: Alumina; Spinel; Refractory; Dilatometry; XRD.

• Abstract:

  The structural development of an alumina (Al₂O₃) and spinel (MgO·Al₂O₃) refractory concrete was evaluated at service temperatures (1000–1600 °C). This material, used in the steel industry, is part of the refractory lining of ladle furnaces. For the study, concrete specimens were cast and cured under ambient temperature and humidity conditions, then dried (105 °C – 24 h) and heat-treated (500 °C – 3 h). Structural variation was analyzed through dilatometry at a constant heating rate (5 °C/min up to 1600 °C) and isothermal dilatometry (4 hours) in the range of 1000–1500 °C. Specimens treated between 1000 °C and 1200 °C showed Al₂O₃ and MgAl₂O₄ as the main phases, while the formation of calcium hexaluminate (CA₆) was observed starting at 1400 °C. Dilatometry indicates that the refractory expands linearly up to around 1100 °C, then accelerates its expansion until approximately 1325 °C, a phenomenon associated with the formation of calcium dialuminate (CA₂). A contraction stage of the concrete occurs between 1330–1460 °C due to the sintering of ceramic grains; this densification behavior is slowed around 1460 °C by the increasing kinetics of calcium hexaluminate (CA₆) formation. From 1540 °C onward, the ceramic sintering process becomes dominant, leading to densification (contraction) of the material. Considering its specific use on the bottom or sidewall of a ladle furnace, and taking into account the different dimensional variations obtained in the isothermal dilatometry tests, the presence of compressive stresses is estimated in regions at temperatures between 1200 °C and 1300 °C, relative to zones at 1000 °C (considered neutral), and tensile stresses in refractory regions exposed to 1500 °C.

• Número de páginas: 16