| High purity strategic metals and alloys are important material support for national strategic emerging industries such as new energy,new materials,equipment manufacturing and electronic information.The separation of impurities and the control of binary alloy composition are the key to the preparation of high purity strategic metals and alloys.Electroslag remelting technology has been widely used in iron and steel smelting because it has the characteristics of slag system countercurrent dynamic interface strengthening impurity removal and electroslag-solidification coupling regulating solidification structure.However,due to the characteristics of melting point,density,oxidation and brittleness of non-ferrous metals,ESR started late and developed slowly in the field of non-ferrous metals.Focusing on the development of ESR in the field of non-ferrous metals,this paper selected two typical objects,Ti-Si binary alloy with low density and high melting point and easy oxidation,and copper alloy with high density and low melting point,to carry out technical basic research in the aspects of ESR system design,electrode structure design,slag washing countercurrent refining and cooling system regulation,and strive to promote the development of ESR in the field of non-ferrous metals.(1)Aiming at the electroslag refining process of Ti-Si alloy with low density and high melting point and easy oxidation,a new five-element electroslag system containing Si O2 and Ti O2 was designed.Combined with the innovation of non-expendable graphite electrode and Ti Si alloy slag washing countercurrent refining method,the efficient removal of alumina inclusion in Ti-Si alloy was realized.Based on the experimental design of electro-slag washing and countercurrent refining,combined with Fact Sage theory calculation,the efficient removal of primary large size Al2O3 inclusions(above 10μm)in Ti Si alloy and the formation mechanism and control method of endogenic small size inclusions(below 5μm)in the refining process were analyzed.In addition,the ESR expansion experiment of Ti Si alloy with non-consumable electrode was completed,and the impurity removal rate of 95.7%was achieved.After refining,the average size of inclusion was reduced to 4.88μm,and the volume fraction was reduced to 0.536%.(2)Different from the traditional electroslag remelting(ESR)rapid cooling to inhibit segregation,a slow cooling and carburizing method for inhibiting segregation of Ti Si alloy was proposed to achieve the synergistic control of impurity separation and microstructure regulation.Four directional cooling rates of 10μm/s,5μm/s,2.5μm/s and natural solidification were designed,respectively.In situ C medium was introduced by graphite crucible to inhibit alloy segregation.The experimental results show that when the cooling rate is 2.5μm/s,the formation of carbides between C medium and Ti and Si elements can effectively inhibit the segregation of the alloy,and the hardness of the alloy is increased by more than 4 times.(3)Aiming at the high density and low melting point refractory copper oxide ESslag refining process,based on the strong affinity between Fe and Al impurities in copper metal and oxygen,a low melting point and high oxidation fluorides esslag system was designed.Combined with the slag washing and countercurrent refining process,the oxidation of Fe,Al and other trace impurities in copper was achieved.The experimental results show that the highest removal rates of Fe and Al are 94.88% and 99.86%,respectively.Through the design of electroslag composition of Ti Si alloy and copper,the selection of non-consumable graphite electrode,the experiment of slag washing and countercurrent behavior and the adjustment of directional solidification process,the feasibility of electroslag remelting technology for the high efficiency of impurity removal and the uniform distribution of tissue composition of non-ferrous metal was verified,and the performance of non-ferrous metal alloys was effectively improved. |
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