Preparation of Lanthanum Doped Tungsten Wire

  In order to make up for the shortcomings of the existing doped tungsten wire with cooling, low thermal resistance and poor photoelectric performance, some researchers pointed out that the performance of tungsten wire can be improved by changing the addition method of lanthanum. The preparation steps of lanthanum-doped tungsten wire are as follows:

(1) Pre-reduction of ammonium paratungstate into blue tungsten in high-purity hydrogen in a reduction furnace;

(2) Wet mixing potassium silicate and aluminum nitrate solution, stirring and mixing and then drying, so that potassium, silicon and aluminum are adsorbed in the blue tungsten gap to obtain doped blue tungsten;

(3) Using a pressure spray gun to spray the lanthanum acid ammonia solution to the doped blue tungsten placed in the doping pot while stirring, and drying after spraying to obtain lanthanum acid ammonia doped blue tungsten;

(4) Put blue tungsten doped with ammonia lanthanide into a reduction furnace, and carry out a reduction reaction in high-purity hydrogen to obtain a coarse powder of reduced tungsten-lanthanum alloy;

(5) Wash the reduced tungsten-lanthanum alloy powder with quantitative hydrochloric acid and hydrofluoric acid to remove excess dopant and other impurities to obtain tungsten-lanthanum alloy powder;

(6) Use an isostatic press to apply equal forces to the tungsten-lanthanum alloy powder installed in the elastic die sleeve to make tungsten billets with uniform density;

(7) The tungsten billet is pre-sintered under the protection of hydrogen to obtain a pre-sintered bar, and then the pre-sintered bar is subjected to vertical melting sintering to obtain a vertical melting sintered bar;

(8) Use rotary forging equipment to forge the vertical melting sintered bar, so that the vertical melting sintered bar section is gradually reduced, the length is increased, and the tungsten structure, grain state and surface state in the billet are changed, and the tungsten rod is obtained;

(9) Anneal the tungsten rod, and then perform rotary forging to obtain a tungsten rod with a diameter of 3.7mm;

(10) Roughly stretch the tungsten rod on the large turntable. After the tungsten rod passes through the die hole on the large turntable, the section decreases and the length increases to obtain thick tungsten wire;

(11) The thick tungsten wire is oxidized and annealed by flame in the air, and then subjected to single-mode stretching with coated graphite and small compression ratio to eliminate work hardening and reduce the tensile strength of the tungsten wire;

(12) The single-mode drawn thick tungsten wire is drawn into the desired thin tungsten wire through multiple modes.