Microstructures and Corrosion Mechanisms in MgO-C Bricks in Contact with High-Basicity and FeO-Rich Slags

Abstract

The MgO-C bricks are extensively used as lining work on different steel containers. Due to the high temperatures of the process, these refractories are subjected to severe wear and corrosion processes, principally in the area of contact with the slag. These slags have variable contents of CaO, SiO2, Al2O3, MgO and FeO, varying in composition according to the process stage. In this paper, cup tests were performed at 1650 °C during 2 hours in air, using two commercial MgO-C bricks. They were put in contact with two different grades of slags, one with high basicity (HB) and the other rich in FeO (RF). The corrosion degree suffered by the refractory materials were analyzed and compared. Microstructural observations were performed in order to postulate the probable corrosion mechanisms acting on each material. The results establish that, in the case of HB slag, the attack is carried mainly through the filler region (matrix). In the case of RF slag attack, it is observed that Fe is the main specie that diffuses through the matrix area of the bricks, and to a lesser extent through MgO grains. In both cases, the quality of the raw material used in manufacturing each refractory bricks, be playing an important role in the corrosion degree.

Resistencia a la corrosión de ladrillos de MgO-C: análisis de la pureza y el tamaño de grano de agregados de magnesia electrofundida

“…Los porcentajes de estos óxidos varían de acuerdo con la etapa del proceso de acería en el cual la escoria es utilizada. En el caso de la escoria seleccionada, utilizada en la industria del acero (típica de un convertidor LD), presenta un considerable contenido de óxido de hierro (del orden del 33 % en peso), lo que la hace una escoria con un importante grado de agresividad a la temperatura de operación (1600-1650°C) (E. Benavidez et al, 2014).…”

“…En las acerías, los refractarios de magnesia-carbono (MgO-C) se utilizan como recubrimiento interno en diversos contenedores de acero líquido, tales como: hornos de oxígeno básico (BOF), hornos de arco eléctrico (EAF), hornos cuchara (LF) y convertidores LD (C. Atzenhofer et al, 2021). Estos materiales están, generalmente, sometidos a temperaturas superiores a los 1600°C (E. Benavidez et al, 2014) (Z. Liu et al, 2018).…”

Estudo comparativo da corrosão de agregados de MgO, com diferentes microestruturas e purezas, por escória de aciaria LD.

“…Segundo alguns autores, a resistência à corrosão e à oxidação dos revestimentos do sistema MC varia de acordo com o tipo de magnésia que é empregado: MgO eletrofundido > MgO sinterizado (BENAVIDEZ et al, 2014(BENAVIDEZ et al, , 2015LEITE;LUZ;PANDOLFELLI, 2014). Essa corrosão dos agregados acontece preferencialmente nos contornos de grãos, portanto, quanto menor o tamanho dos cristais, maior será sua área superficial e maior a reatividade no processo de corrosão (YAMAGUCHI, 1997).…”