A Study On The Fabrication Technology And Mechanical Properties Of Al₂O₃ Matrix Nano-composite Ceramics And The Research Of Nano-composite Ceramic Liner In The Tuyere For A Blast Furnace

In the experiment, Al₂O₃ powder was the matrix material of nano-composite ceramics. Using ZrO₂ powder and SiC power as strengthening phase powder respectively, two series of nano-composite ceramics, for example, Al₂O₃-ZrO₂ and Al₂O₃-SiC was studied. The Al₂O₃ matrix ceramics was successfully made by means of pressureless sintering. Preparing technology, mechanical properties, micro-structure, thermal shock resistance of Al₂O₃ matrix nano-composite ceramics were also deeply studied in the experiment.In the process of studying Al₂O₃-SiC nano-composites ceramics, the SiC powder oxidation in the process of its sintering in the air was studied. When sintered in the air, the SiC powder has apparent oxidation and the oxidation phenomenon has kept strengthening with decreasing of grain size of SiC and increasing of quantity of SiC power. Results of XRD revealed that the SiC diffraction peaks disappeared in the sintered sample, which provided some evidence for the oxidation of SiC under high temperature. Because of existence of the oxidation, there were lots of pores and glass phases in the sintering sample, which made the sintering characters of the sample degrade.In the process of studying Al₂O₃-ZrO₂ series ceramics, effects of ZrO₂ addictive on density and micro-organization of material were analyzed. Results revealed the effect of that ZrO₂ addictive could enhance sinterability and decrease the sintering temperature. When there was small amount of ZrO₂ powder, ZrO₂ particles existing in interspace between the Al₂O₃ particles can prevent the neck formation, which enhanced the sintering density of sample. With increasing amount of ZrO₂ power, there were more chances for ZrO₂ particles to contact with each other, which increased the sintering temperature. When the amount of ZrO₂ additive was over a particular limit, ZrO₂ particles gathered, which made many properties of ZTA ceramics deterioration. When addition of ZrO₂ was small, the size of Al₂O₃ matrix grains grew bigger abnormally. In contrast, when addition of ZrO₂ increased, the tendency of abnormal growth of Al₂O₃ matrix grains was obviously prevented in the sintering process. In this way, structure and properties of ZTA ceramics were improved.Many experiments confirmed that Al₂O₃-ZrO₂ ceramic series is suitable for sintering in air; the best sintering condition is under 1590℃and heat preservation for an hour. In this way, we can get ceramics with satisfying mechanical properties. The relative density is 98.57%, the bending strength is 485.23MPa, the fracture toughness is 6.60MPa·m^1/2, the Vichers hardness is 13.11Gpa. The ceramic material has shown an excellent thermal shock resistance, because the prepared ceramics can endure more than 50 times of thermal cycle of 1200℃.Because of the excellent mechanical properties and thermal shock resistance of Al₂O₃-ZrO₂ series ceramics, liner made of the ceramic materials was successfully enchased in the tuyere of blast furnace. The service-life of tuyere will increase and energy consumption of blast furnace will decrease. The tuyere enchased with ceramic liner have been installed on the blast furnace for more than 50 days, and they are running well these days. Other technical norms should be tested in the future.