A new form of tungsten and a process for its preparation

摘要

Tungsten is prepared by reducing WF6 in the vapour state with an excess of hydrogen in a fluidized bed of refractory metal seed particles, which may be of W, Mo, Ta or Nb, at a temperature sufficiently high to bring about reduction of the fluoride and deposition of W on the seed particles. The particles produced comprise a fine microstructure of tungsten grains having a width and thickness of 0.1-2 microns and length at least six times their width, the microstructure having a Knoof hardness of more than 900, a density of at least 95% of the theoretical density of tungsten and undergoing less than 20% recrystallization upon being subjected to a temperature of 1595 DEG C. for 3 hours. The particles may be formed into bars or billets by gas pressure bonding, the bars or billets being then rolled, swaged or forged, e.g. to sheet form, or extruded into wire. The particles may be packed into gas-tight, thin-walled containers which are subjected to gas pressures of 350-1400 Kg./cm.2 and tungsten annealing temperatures, e.g. 1090-1930 DEG C., for the production of rocket nozzles and nose cones. In reducing the tungsten hexafluoride a reactor 3, Fig. 16, may be used, the reactor being formed of high nickel content alloys of copper and nickel. WF6 and H2 are introduced through lines 9 and 10 and the seed particles through line 11. Heating means 12 such as electrical resistances, induction heaters or a gas fired furnace, are provided for reaction zone 5. The reaction temperature may be between 205 DEG C. and 1090 DEG C. but is preferably not over 995 DEG C.