Refractory metal

• Overview

  Refractory metals generally refer to metals (tungsten, rhenium, tantalum, molybdenum, niobium, hafnium, chromium, vanadium, zirconium, and titanium) with melting points higher than 1650℃. The alloys formed by these metals as matrix and adding other elements is called refractory metal alloys. Tungsten, molybdenum, tantalum and niobium are themostly usedrefractory metals in the manufacture of structural materials with high temperature above 1093℃ (2000°F).

• Advantage

  The most important advantages of refractory metals are good high temperature strength and good corrosion resistance to molten alkali metals and vapors.

• Disadvantage

  The main disadvantage of refractory metals is poor oxidation resistance at high temperature. Tungsten and molybdenum have high plasticity-brittle transition temperature and are difficult to be processed at room temperature. The machinability, weldability, low temperature ductility and oxidation resistance of niobium and tantalum are superior to those of molybdenum and tungsten.

• Application

  Refractory metals are still widely used in metallurgy, chemical industry, electronics, light source, machinery industry and other sectors, although they have defects such as toughness and poor oxidation resistance.

  
  

  The main uses are:

  (1) Molybdenum and niobium are used as additives for iron and steel and non-ferrous metal alloys. The amount of molybdenum and niobium in this respect accounts for about 4/5 of the total amount.

  (2) Used for manufacturing cutting tools, mining tools, processing die and other hard alloy, tungsten in this aspect accounts for about 2/3 of the total consumption, tantalum, niobium and molybdenum are also important components of hard alloy.

  (3) It is used as filament, cathode, capacitor and contact material for electronics, electric light source and electrical departments, among which the amount of tantalum in capacitors accounts for 2/3 of the total amount.

  (4) In addition, it is also used in the manufacture of corrosion resistant parts, high temperature and high vacuum heating body and heat shield, armor piercing core, radiation protection materials, instrument parts, hot working tools and welding electrodes, etc.