"Mechanical Behavior of MgO-C Refractory Bricks Thermally Treated In Low Temperature Range"

S.E. GASS; A. G. TOMBA MARTINEZ; P.G. GALLIANO; N. BELLANDI

Congreso; 16th Biennial Worldwide Congress on Refractories UNITECR?17; 2017

Steelmaking refractories performances have a strong impact on critical aspects of the industrial process, such as production costs and steel quality, between others. In this paper, the effects of thermal treatments on the mechanical behavior of MgO-C refractory materials are assessed using two non-oxidant atmospheres, argon flow and graphite bed, in addition to combination of both of them in different stages.Non-commercial bricks with and without antioxidant are evaluated using cylindrical testing specimens (diameter: 30 mm, length: 45 mm). Microstructural and textural changes as consequence of heat treatments at temperatures < 1000ºC during 1h or 3h prior to mechanical test were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM/EDS). As received materials, as well as those thermally treated, are mechanically tested in compression between room temperature and 1000ºC (in Ar) to obtain the stress-strain relationship in each case.Stress-strain curves change according to alterations in the microstructure and texture of the brick, due to the events taking place during the different stage of thermal treatments prior and during mechanical tests (heating, permanence and cooling). Furthermore, the time of exposition is considered as a variable to evaluate the effect of different advance in the processes which occur during the thermal treatment. In the range of low temperatures (T < 1000ºC), the organic binder is the main component affected by thermal variations; however, the antioxidant additive actually affects the mechanical behavior even its reaction occurs at temperatures above 600ºC. The results obtained in the range of low temperatures can be interpreted taking into account factors such as mass losses (volatile elimination and carbon oxidation), thermal shrinking and expansion, and cracks healing.