Tantalum niobium ore is the main raw material for tantalum production, but tantalum niobium ore is often accompanied by a variety of metals, so the main step of tantalum smelting is to decompose the concentrate, purify and separate tantalum and niobium, in order to make tantalum and niobium pure compounds, and finally make metal. For pure tantalum ingots fused by electron beam, 4mm thick plates are obtained by forging and rolling the ingots, and 1mm and 1.6mm thick plates are obtained by cross rolling. Recrystallization annealing was carried out at 900℃, and the holding time was 15, 30 and 45min respectively. Finally, the specimen was broken under the condition of strain rate of 20mm/min. Preparation of tantalum metal by reducing pure tantalum compounds into tantalum metal. The raw materials of pure tantalum compounds are tantalum pentoxide, tantalum pentachloride, tantalum pentafluoride and fluoride (e.g. K2TaF7). Reductants include active metals such as sodium and magnesium, as well as carbon and hydrogen. The melting point of tantalum is as high as 3669K, so the reduction results in powdered or spongy metal. A dense metal is obtained by further smelting or refining.
After the annealing temperature of recrystallization was selected to be 900℃ and respectively kept for 15, 30 and 45min, the microstructure of the sheet samples with thickness of 1 and 1.6mm was observed. The results showed that the deformed microstructure was basically eliminated, but the recrystallization microstructure refinement effect was not obvious. When the cold deformation is small, the high recrystallization annealing temperature should be used to refine the grain. The samples with thickness of 1 and 1.6mm were predeformed by 10% and 20% respectively, and then recrystallization annealing was carried out at 900℃. After treatment, the hardness and tensile strength of the two samples were improved, while the elongation was significantly reduced. After 15, 30 and 45 minutes of insulation, the hardness of tantalum gradually increased with the extension of the insulation time, and the elongation decreased successively. With the extension of the insulation time, the yield strength of materials with different thickness of the plate gradually increased, but the change of tensile strength was different. The tensile strength of 1mm thick plate gradually decreased, while that of 1.6mm thick plate first decreased and then increased. The morphology analysis of the tensile fracture shows that after pre-deformation and heat treatment, the material changes from ductile fracture to brittle fracture, and the fracture mechanism is mixed fracture, which is composed of intergranular fracture, cleavage fracture and ductile fracture.
