The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied ...The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.展开更多
The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ra...The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ray diffraction and scanning electron microscopy after the samples were subjected to a heat treatment based on the temperatures of the affected, transition, and original layers of zirconia metering nozzles during the continuous casting of steel. The results showed that, after heat treatment at 1540, 1410, or 1300A degrees C for a dwell time of 5 h, the monoclinic zirconia phase was gradually stabilized with increasing heat-treatment temperature. Moreover, a transformation to the cubic zirconia phase occurred, accompanied by grain growth, which illustrates that the temperature gradient in zirconia metering nozzles affects the mineral composition and microstructure of the nozzles and accelerates damage, thereby deteriorating the quality and service life of the nozzles.展开更多
In this paper we present the results of studies on making MgO zirconia sintered parts（ intended to be used as metering nozzles in continuous casting of steel） from monoclinic zirconia and MgO powders via a granulati...In this paper we present the results of studies on making MgO zirconia sintered parts（ intended to be used as metering nozzles in continuous casting of steel） from monoclinic zirconia and MgO powders via a granulation process. The parts were pressed and sintered under different conditions,and analysed for physical properties,microstructure and phase composition. We found a strong influence of the MgO concentration and the sintering cycle,especially the cooling rate on the thermal shock resistance. The paper concludes with recommendations for the production of zirconia metering nozzles in an economic way.展开更多
基金funded by the National Natural Science Foundation of China(51372193)the Natural Science Basic Research Plan in the Shaanxi Province of China(2014JM6224)
文摘The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.
基金financially supported by the National Natural Science Foundation of China (No. 51372193)
文摘The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ray diffraction and scanning electron microscopy after the samples were subjected to a heat treatment based on the temperatures of the affected, transition, and original layers of zirconia metering nozzles during the continuous casting of steel. The results showed that, after heat treatment at 1540, 1410, or 1300A degrees C for a dwell time of 5 h, the monoclinic zirconia phase was gradually stabilized with increasing heat-treatment temperature. Moreover, a transformation to the cubic zirconia phase occurred, accompanied by grain growth, which illustrates that the temperature gradient in zirconia metering nozzles affects the mineral composition and microstructure of the nozzles and accelerates damage, thereby deteriorating the quality and service life of the nozzles.
文摘In this paper we present the results of studies on making MgO zirconia sintered parts（ intended to be used as metering nozzles in continuous casting of steel） from monoclinic zirconia and MgO powders via a granulation process. The parts were pressed and sintered under different conditions,and analysed for physical properties,microstructure and phase composition. We found a strong influence of the MgO concentration and the sintering cycle,especially the cooling rate on the thermal shock resistance. The paper concludes with recommendations for the production of zirconia metering nozzles in an economic way.
