Basic Research On The Preparation Of Ti-Si-(Al) Alloy By Reduction Of Titanium-containing Blast Furnace Slag By Aluminum

The titanium-bearing blast(Ti-BF)furnace slag is important secondary resources for titanium extraction,which is typical by-product of blast furance process.At present,there is still not found econnomic and effective method to recycle Ti from the very slag.A series of problemes has caused because of the nontreatmnet of these slag,including recource waste,water pollution,land occupation etc.From the point of solid waste recycling utilization and low-cost preparation of Ti-Si-Al alloy,a process for preparing Ti-Si-(Al)alloy involving isothermal reduction followed by directional solidification was proposed.The thermodynamic study of aluminothermic reduction of Ti-BF slag shows that TiO?Ti is the most difficult process during the reactions of Al with TiOx.Thus,the limit of TiO?Ti can be the equilibrium point of the whole reaction system.The distribution coefficient of Ti(LTi)between slag and melt was deduced.The analysis result indicates that increasing the addition of reductant and adding appropriate flux(calcium oxide)can improve LTi.The recovery of Ti will improved correspondingly.Theoretical analysis shows that the Ti-Si-Al alloy with small amount of Fe?Mn will be obtained.The oxides present in formed slag will be CaO?Al2O3 and MgO.The reduction experiment showed that the recovery of Ti and Si can achieve 97.43%and 93.68%respectively,with adding a certain amount of CaO(24%)and Al(40%).Meanwhile,the content of TiO2 and SiO2 present in slag decreased to 0.43%and 0.67%respectively.The main phase present in prepared alloy include TiSi2?TiSi?Ti5Si4 and small amount of Fe2SiTi and FeSi2Ti.The formed slag is mainly composed of CaAl2O4 and MgAl2O4.The reduction experiment was carried out in magnesia crucible,corundum crucible and graphite crucible to research the erosion of refractory lining caused by molten slag during metallurgical process.Experiment investigation shows that alloy can separate from slag easily when the addition of CaO exceeds 16%,as the reactor vessel is magnesia crucible and corundum crucible.It should be pointed out that the erosion of refractory lining caused by molten slag tend to be severe when the addition of CaO exceeds 16%.The optimum additive of CaO in magnesia crucible and corundum crucible is 16%and 24%.The recovery of Ti can reach 99.73%and 97.76%respectively at the same time.The molten slag will not erode refractory lining made by graphite.The optimum additive of CaO in graphite crucible is 16%.In view of production cost,the recovery of Ti and other factors,taking magnesia refractory as furance lining of smelting furance will be appropriate during the smelting process of Ti-bearing blast furance slag.The directional solidification separation technology is used for preparation of titanium-silicon alloy with little Al.The results show that the optical delamination will more clear with the decrease of withdraw rate.Through the chemical analysis and phase analysis of different parts of ingot(5?m/s);we reached the conclusion that from the bottom to top of the alloy,the extensive enriching order of elements in melt during directional solidification process is Ti?Si?Fe+Mn?Al and the process of phase transformation is TiSi2+Si?Si?Al+Si+Al3FeSi2?Al+Si.