Study On Fluidity And Structure Of Blast Furnace Slag Bearing High Al₂O₃

Slags are very important to producing high quality steel in the holly ironmaking and steelmaing. The old adage “Look after the slag and the metal will look after itself” is the summay in actual production and it is very appropriate. In recent years, the compiteion beteewn steel companies is fierce due to production fast growth and over capacity. The company's first task is reduce the costing by perchasing and utilizating low grade ore. Howerver, extensive use the low grade ore brearing high Al₂O₃ which will increase the content of Al₂O₃ in blast furnace slag and influence normal BF operation. The theory based on silicate slag system can not meet the requirement of aluminosilicate BF slag, the campany can not efficiently use cheap ore bearing high Al₂O₃ lead to reducing the competitive abilty. Therefore, the salg has appropriate liquidty and other metallurgical performance is essential to ensure BF high quality and efffective production. Studing the effect of Al₂O₃ content on chemical and physical properties and strcture of metallurgical slag, it can help to clarify how Al₂O₃ take the role as amphoteric oxides and provide scientific basis and technical support for company large-scale use of high alumina ore in future.The effect of Al₂O₃ and Al₂O₃/SiO₂ ratio on the viscosity of the CaO-SiO₂-Al₂O₃-MgO-TiO₂ slag system was studied in the present work. At fixed CaO/SiO₂ ratio of 1.20, 9 mass% MgO and 1mass% TiO₂ of, the viscosity increases with increasing Al₂O₃ content at the range of 16-24 mass% due to the polymerization of the aluminosilicate structures, while the decreases when the Al₂O₃ is higher than 24%, meaning that Al₂O₃ acts as a network modifier at higher content. Increasing Al₂O₃/SiO₂ form 0.47 to 0.92 cause a slight decrease of viscosity of the slags and had an opposite effect when Al₂O₃/SiO₂ more than 0.92. The free running temperature increase with Al₂O₃ content and appeared to show a peak at CaO/SiO₂ ratio of 0.92. The change of the apparent activation energy is quite in accordance with the change of viscosity. When Al₂O₃ content more than 24 mass% with low SiO₂, CaO content range from 35mass% to 45mass%, the slag transform from silicates-based to aluminates-based can still get a good operation region.Molecular dynamic simulation use to calculate the microstructure of quenched CaO-SiO₂-Al₂O₃-MgO-TiO₂ systems. The present simulation demonstrates the atom bond length with Si-O<Al-O<Ti-O<Mg-O<Ca-O<O-O and atom diffusion capacity with Ca>Mg>O>Al>Si in the slag system. In present condition and chemical composition, the simulation result show more than 90% of the Al particles exist as four coordination, about 5% exist as five coordination and less than 2.5% exist as three coordination.Studing CaO-Al₂O₃ slags system structure change with Al₂O₃ content. We analysise Raman spectral peaks of crystal and non-crystal to determine the characteristic Raman peaks of 3CaO·Al₂O₃, CaO·Al₂O₃ and CaO·2Al₂O₃ crystal, we found peaks located in 357cm^-1?520cm^-1and 543cm^-1 respectively. Raman spectra use to research CaO-SiO₂-MgO-Al₂O₃-TiO₂ slag system's structure at 1500?. Author establish the quantitative relationship beteewn structure and viscous active energy though Newtonian fluid's Arrhrnius formula, and the quantitative relationship beteewn pre-exponential factor and viscous active energy by Temperature compensation relationship, finaly get quantitative relationship between the structure of the polymerization with the viscosity.