Análisis por elementos finitos de alúmina sometida a esfuerzos mecánicos y térmicos

Disks of a commercial alumina were fabricated by slip casting, calcination and sintering. The surfaces were machined using SiC papers (120 and 320 grit) and characterized by residual stresses measurements. The mechanical strength was determined in biaxial flexure (ball on discontinuous ring). The specimens were subjected to thermal shock conditions (cooling using a high-velocity air jet) and the critical temperature differential for crack propagation was determined. The temperature and stress distributions during air impinging were calculated using a finite element method. The value of the heat transfer coefficient was estimated by fitting the calculated temperature profiles with those measured during each test. The calculated tension for the thermal shock fracture was compared with the mechanical strength, together with the fracture features in each case. The differences were explained on the basis of the calculated stress distributions

Impact of the reduction of graphite content in critical properties of MgO–C bricks for steelmaking industry

Nowadays, the use of lower amounts of graphite in MgO–C bricks for the steelmaking industry is motivated by several reasons, including the reduction of CO2 emissions. In this work, a MgO–C brick with 12 wt% graphite, was evaluated in comparison with a similar material containing just 8 wt% of this component. The changes induced in the brick by thermal treatments (graphite bed) between 500 and 1400 °C were analyzed comparatively. Moreover, the effect of reducing the graphite content in the mechanical properties at RT, 1000 and 1400 °C (compressive tests, in argon) and the oxidation resistance in air at 1000 and 1400 °C was determined. At 1000 °C, the refractory with 8 wt% graphite exhibited the highest mechanical strength and stiffness. Furthermore, although the decarburized area was larger after treatment at 1000 °C in air in this brick, the mass and carbon losses showed the opposite trend