2014 Volume 54 Issue 8 Pages 1849-1855
For continuous measurement of molten steel temperature, this work proposed a novel structure of blackbody cavity sensor to overcome the shortcomings of the traditional sensor. The traditional sensor had slow response speed and poor thermal shock resistance, which was due to its double layer tubes and thermal stress concentration in the closed bottom of an inner corundum tube respectively. The double layers included an outer protective tube of Al2O3–C refractory and the inner tube which formed the blackbody cavity and isolated the fume generated by the outer tube. The novel structure was composed of a measurement cavity of an Al2O3–C tube and a fume exhaust system. The fume exhaust system, including an inlet, an exhaust pipe and two outlets, eliminated the fume influence of obstructing the optical path. Furthermore, the fume exhaust system was based on the relationship between the fume and temperature distribution. Results showed that the fume formed below approximately 1320°C, meaning the fume existed in and above the slag layer in the internal cavity of the sensor. The open bottom of the exhaust pipe should locate at the interface between the slag layer and molten steel to remove the fume. Additionally, the sensor should dip into molten steel up to 220 mm for high accuracy. It improved the response time from 340 to 240 seconds and enhanced the thermal cycling times from about 4 to beyond 10 times.