Tantalum technical parameters
The boiling point of tantalum is 5427°C and the melting point is 2996°C. It is a refractory metal and its melting point is higher than other commonly used metals. Tantalum starts to react with oxygen at 300°C in the air, reacts with nitrogen at 700°C, and reacts with nitrogen at 350°C in hydrogen-containing gas. It starts to react with hydrogen and starts to react with nitrogen at 300°C in ammonia gas, both of which will produce brittle compounds. Therefore, if tantalum equipment and containers come into contact with air during operation, the operating temperature should generally not exceed 250°C. Only if they are not in contact with air and other environments can they be considered for use at higher temperatures. The welding and heat treatment of tantalum should be carried out in vacuum or under the protection of inert gas, that is, the thermal process above 300°C should be carried out under the protection of vacuum or inert gas. Tantalum is commonly used for inert gas shielded welding. The purity of argon should not be less than 99.999%. Not only the welding pool should be protected by inert gas, but also the weld and heat-affected zone that are cooling after welding should be protected by inert gas when the temperature is above 250°C. Therefore, a protective drag cover is required. It is more suitable to stop supplying inert gas when the temperature drops below 200℃. It should be ensured that the surface of the welded joint and each weld is silvery white or light yellow. The light blue should be rubbed away, and no dark blue, off-white or white powder should appear.
Tantalum sheet are mainly used as corrosion-resistant materials. A Ta2O5 film is formed on the tantalum surface, which has good corrosion resistance. Generally speaking, the corrosion resistance of tantalum is better than that of titanium, zirconium, and niobium, and it can be considered an engineering material with better corrosion resistance. Tantalum often has excellent corrosiveness in strong corrosive media such as nitric acid, aqua regia, hydrochloric acid, phosphoric acid, and organic acids. However, it cannot be considered that tantalum can resist corrosion in any corrosive media, such as fuming sulfuric acid and hydrogen at certain temperatures and concentrations. Fluoric acid, hydrosilicic acid, fluorosilicic acid, fluoroboric acid, sodium hydroxide, potassium hydroxide, potassium nitrite, aluminum chloride, aluminum fluoride, chlorine, bromine (in methanol) and other media solutions have been obtained. Results of use or testing of poor corrosion resistance or corrosiveness. Tantalum and tantalum alloy pressure-processed materials can be manufactured by vacuum arc or vacuum electron beam melting or by powder metallurgy. Since the mechanical properties of powder metallurgy products are sometimes not stable enough, with low plasticity and poor welding performance, they are generally no longer used in pressure vessels and are only used in fluid components of fluid machinery.
Tantalum and tantalum alloys have been widely used in pressure vessels, but there are no specific contents in the official pressure vessel standards of various countries. Pressure vessels are mainly made of pure tantalum, which has good corrosion resistance and plasticity. Ta-2.5W and Ta-10W tantalum alloys are only used when higher strength is required.
Oxygen, nitrogen, hydrogen and carbon in tantalum can generate interstitial solid solutions in tantalum. When the content exceeds the solubility, a second phase will appear, reducing the plasticity of tantalum. Adding tungsten to tantalum will increase the melting point of tantalum and increase the high-temperature strength of tantalum.