First, tungsten and molybdenum are the same family of refractory metals. Tungsten theoretical density density: 19.35 g / cm3, melting point: 3410 ± 20 ℃. Molybdenum theoretical density 10.2 g / cm3, melting point 2610 ℃.
Second, the tungsten and molybdenum smelting methods are generally three: powder metallurgy, electron beam melting and vacuum arc melting. From the process, the latter two methods have a melting process, the first way there is no melting process. However, from the scope of application and material performance, the powder metallurgy process has an absolute dominant advantage. This is also related to the powder metallurgy process can be in the metal grain morphology control and dispersion of alloy production has a melting process does not have the natural advantages.
The process of rolling and forging has a very critical effect on the final density and grain orientation of the material. As the tungsten and molybdenum products, the ductility is relatively poor, so the machining is relatively difficult.
After sintering the material density is generally 90% -98%, through the sintering to reach 100% of the theoretical density of materials is absolutely not
can. Through rolling and forging, the relative density of the material can reach more than 98%.
Third, tungsten and molybdenum materials are often used in different industries due to the following nine properties.
1) high melting point
2) Very low vapor pressure (which is especially important for applications of refractory and vacuum industries.)
3) high temperature physical strength (for high temperature environment in the structural parts)
4) creep resistance (high temperature load structural parts. High dimensional stability. Such as: large aircraft engine turbine blade forging die.)
5) High elastic modulus
6) Very low coefficient of thermal expansion (for metal-ceramic construction, metal-semiconductor structure, metal-graphite structure is very
important. Such as in the LED field, is considered high-power LED future V-LED will use molybdenum or molybdenum copper material as the base material)
7) Excellent electrical conductivity (metal properties)
8) Excellent thermal conductivity (metal properties)
9) Selective resistance to erosion
Fourth, tungsten and molybdenum rods, sheet metal through mechanical processing, electrical processing, etching, etc. made of a variety of products. Such as crucible, heat shield, boat, target, ion implant, sapphire thermal field accessories, molybdenum gate and so on.
