Tantalum and tantalum alloy plates, strips and foils are high-temperature and corrosion-resistant materials. Their chemical stability is similar to that of glass, and their strength and rigidity can be comparable to those of low-carbon steel. Their high-temperature thermal strength is second only to tungsten and tungsten alloys, making them excellent materials for chemical anti-corrosion and high-temperature furnaces. Tantalum reacts strongly with oxygen, hydrogen and nitrogen in the air above 300℃ to form brittle compounds, increasing the hardness of the metal and reducing its brittleness, which has a significant impact on the plastic-brittle transition temperature of the metal.
Tantalum ingots are smelted by electron beam - forged into billets at room temperature (or less than 400 degrees) - annealing - rough rolling - annealing - strip rolling - annealing - foil rolling - heat treatment
1 Forging requirements
Forging blanks is best done by cold forging with a forging press, and the forging temperature should not exceed 400 degrees. Cold forging has a large contact surface and good material uniformity, which can reduce the pollution of gas impurities.
2: Rolling Requirements:
Cold rolling is usually adopted, with the total processing volume controlled at 80% to 90% of the slab thickness, and the processing volume of each pass controlled at 6% to 8% of the slab thickness. To ensure the surface quality of the rolled plate, it is required that the forged slab be free of defects, pollution and have a smooth roll surface.
3: Clear requirements:
Tantalum must be pickled before annealing to remove the surface contamination layer. The pickling solution is prepared by mixing 65%-68% nitric acid, 95%-98% sulfuric acid and hydrofluoric acid in a volume ratio of 5:5:2. Wash with water after acid washing.
Process performance and requirements
Formability
Tantalum has good plasticity and can be processed by cold forging, rolling, punching, drawing, spinning, extrusion, bending, etc. Hot working needs to be carried out under the protection of inert gas. After an oxide film is formed on the surface of its high-performance strip, it can be continuously deep washed six times to be processed into circular cup bodies.
2: Heat treatment process
Heat treatment is carried out under vacuum conditions at 1200 to 1300℃. The holding time is determined based on the material loading and thickness. During recrystallization annealing, the foil materials must not be stacked.
