| The titanium alloy represented by Ti-6Al-4V has excellent properties,which has important strategic significance in aerospace and defense industry.As the essential raw material for producing titanium alloy,V-Al alloy,is the key to titanium alloy’s quality and output.But at present,only United states and Germany master the smelting method of V-Al alloy in aerospace grade.In China,as main technologies for preparation of V-Al alloy,out-of-furnace method,two step method and electro-aluminothermic method have the shortcoming:low recovery,uniformity,long processes and high carbon content,etc.Therefore,it’s urge to explore independent intellectual methods for preparation of V-Al alloy in aerospace grade because of short processes,small pollution,low cost and low impurity.However,the 98 flake shape vanadium pentoxide has a number of impurities,so it cannot meet the need of preparation of V-Al alloy in high quality.Meanwhile,the smelting slag of V-Al alloy,if can’t recycle,not only causes the environmental pollution but also wastes resources.So this paper,based on preparation method of V-Al alloy in high quality as well as taking raw material purification and slag recycling into consideration,explored a feasible technological process for alloy preparation from beginning to end,and provided reference for the industrialization of V-Al alloy.Metallurgical grade 98 flake V2O5,as raw material,was leached by NaOH solution in two stages.Metal ions such as Fe3,A13+ and nonmetal ions such as SiO32-PO43-in leaching solution were removed by hydrolysis precipitation and precipitation method,respectively.After vanadium precipitation in weak alkaline solution,washing and calcinations,V2O5 could be obtained in high purity of 99.9%,which could be used for preparation of aerospace grade V-Al alloy.The introducing approaches of impurities in the process of producing high-quality V-Al alloy were analyzed.Studies showed that raw materials in low purity,such as 98 flake V2O5 and A1 particles,were the main sources of impurities such as Fe,Si in alloy.By using raw materials in high purity could reduce the contents of impurities.The impurities:Cr,Mg and C in alloy mainly came from the refractory materials and graphite materials.The impurities in refractory materials could be avoided by selecting reasonable smelting method and refractory materials.A new method of preparing high-quality V-Al alloy by electrothermal reduction-two steps refining was proposed.The smelting processes of high-quality V-Al alloy by electrothermal reduction-two steps refining process were studied and determined.The results showed the optimum conditions were as follows:the high-purity V2O5,99.7%of Al and AR-grade CaO as raw materials,parallel electrodes DC arc furnace as smelting equipment,corundum as lining materials,the consumption of the reducer as same as theoretical consumption,fluxing medium equivalent to 90wt%of theoretical quantity and compound reducing agent correspond to 3wt%of the reducer,open arc as smelting mode,the inclusion and gas removed by argon stirring.Under these conditions,V-Al alloy could be obtained which complied with GfE’s aerospace-grade V-Al alloy standard.The alloy was uniform and compact without visible bubbles and inclusions,with 97.25%of V recovery rate,about 12%of A1 content,0.12%of iron impurity,0.09%of Si,0.09%of C.The preparation of AlV55 alloy was explored and the existing problems and the direction of further research were proposed.The main phase of the slag was 7Al2O3·12CaO and CaAl2O4 and the slag contained 0.8%of V;Thermodynamic analysis showed that they could be leached by mixed lye in normal atmospheric temperature spontaneously.The optimum technological conditions of extracting Al2O3 from the slag were studied and determined.Experimental results showed that with 210g/L of Na2CO3,40g/L of NaOH,leaching at 90℃ for 120mins,liquid-to-solid ratio of 6,the leaching rates of Al2O3 and V reached 88.74%and 80.22%,namely with 0.785g/L of the concentration of V in the solution. |
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