antalum has an extremely hard texture and the hardness of 6-6.5. Tantalum is a kind of rare metal with steel grey luster, and has the melting point of 2,980℃ and the density of 16.6g/cm3. With similar performance of niobium, tantalum is an extremely stable chemical element. With high ductility, tantalum can be stretched into thin filaments or prepared into thin foils. It has extremely small expansion coefficient, only 6.6 PPM expansion after each centigrade increase. Besides, it has extremely high tenacity which is more excellent than that of copper.