Effect of Firing Temperature on Mechanical Properties of Al₂O₃–C Sensor for Continuous Measurement of Molten Steel Temperature

Abstract

Al₂O₃–C sensor based on the blackbody cavity theory achieved a continuous measurement of molten steel temperature. Its mechanical properties were affected by the firing temperature. Firing temperature has great influences on the weight changing, decalescence/heat release reaction and structure evolution of the resin binder used for Al₂O₃–C sensor. Results showed that the porosity increased and the strength declined below 750°C, main exothermic reaction and weight loss of the binder occurred. As the firing temperature increased to 800°C, a great enhancement of endothermic reaction and a drastic increase of crystallite size were observed, relating to the rapid shrinkage of the binder. The porosity decreased from 10.3% to 8.8% and the strength improved remarkably from 6.5 to 8.2 MPa in this temperature range. Strengths and porosities of the sensors fired under 800–950°C were similar (8.2–8.5 MPa and 8.8%–8.4% respectively). Moreover, the temperature response and lifetime of the sensor fired at 800°C were almost equal to the sensor fired at 950°C according to industrial tests, which were about 165 s and 24 h.