Study On Preparation Of High Titanium Ferroalloy By Thermite Method And Its Deoxidizing Performance In Molten Steel

High titanium ferroalloy which contains65～75%titanium is a kind of special type ferroalloys with wide applications and is a important raw material of smelting special steel, structural steel and special alloy steel. Mainly used as deoxidizer, degassing agent, alloy additive and inoculant. With the improving of steel quality, the increasing of steel varieties, the demand to the quality and variety of titanium ferroalloy is increased.Group prepared the low-oxygen high titanium ferroalloy by the new technology, but have the problem of high aluminium content, so our group prepared the low-oxygen high titanium ferroalloy of the different aluminum content. Effect on titianium and aluminum deoxidizing behavior and steel organization in the deoxidizing process.Firstly, by calculating the thermodynamics of precipitating Ti-oxidized products, the results show Ti2O3will always prior precipitate, then TiO2and Ti3O5, and finally TiO with dissolved oxygen content below0.003%when the deoxidation with Titanium in1873K. The actual system is Ti-Al complex deoxidizer, and the oxygen in molten steel are controlled by Ti, Ti2O3is deoxidation products when aTi/aAi>8in1873K.In fact, Al2O3and Ti2O3can take shape solid solution, so when aTi/aAi>10in molten steel can ensure the α(Al2O3)was so small in deoxidation products that the Ti2O3was mainly deoxidation products.Secondly, the high titanium ferroalloy was prepared using rutile and ilmenite as raw material.The effects of type and dose of different rutile and ilmenite proportioning, dose of different aluminum contents and different weight material on the quality of high titanium ferroalloys have been investigated.The high titanium ferroalloys were characterized by XRD and chemical analysis.The results show that:when mass ratio of ilmenite and rutile is1:2, content of titanium and aluminum in alloy and the recovery are best; excessive levels of aluminum in the ingredients,was the directly reason to led to excess aluminum in the alloy, so it was important to control the aluminum contents reasonable; with the increasing of material, aluminium content is reduced,but the recovery of titanium is reduced; through computation unit heating of each group experiment that the most appropriate unit heat is2800-3000KJ/kg.Finally, the high-temperature melting experiments were carried out in the medium frequency induction furnace using different alloys to deoxidize. The chemical composition, organization and inclusions of samples that deoxidized by different combinations of alloys were analyzed by chemical analysis, metallographic microscope, scanning electron microscope and energyspectrum analysis. The results show titanium ferroalloy deoxidizing is a Ti-Al complex deoxidation process.After alloy was added, having a microstructure refining effect and needle-like ferrite were appeared, these change plays the main role.is titanium elements.Follow the inclusion analysis, we can see that inclusion and surrounding microstructure have significantly changes after alloy was added, most of inclusions containing Al and Ti, still contain a small amount of Mn elements.Inclusion is basically silicates and Al2O3, at the same time, inclusion sizes get smaller. With the increasing of the deoxidizer, the silicates inclusion were getting less and less and mainly Ti-Al-Mn complex inclusion.These inclusions around appeared the radial or part radial needle-like ferrite microstructure.The results show that the type of inclusion played a role of intragranular ferrite core, could the precipitation of intragranular need-like ferrite, turned the harmful of the inclusion into the benefical and having a microstructure refining effect.