Preparation for Tungsten Tubes by Rare Earth Lanthanum Doping

Tungsten tube is a kind of product of many tungsten products. At present, the methods of making tungsten tubes are mostly made of powder metallurgy or chemical vapor deposition. The tungsten tubes obtained by powder metallurgy are easy to crack and have high brittleness when they are installed and used at room temperature. While the chemical vapor deposition process needs to use or produce harmful gas in the process of production, and the environmental protection performance is low.

In industrial practice, some scholars use the powder metallurgy method to doping rare earth lanthanum in tungsten powder, which can effectively solve the brittleness defects of tungsten tubes. Compared with WF₆ gas phase deposition, this method can avoid producing harmful gases. The general content of the doping is as follows:

(1) The cold isostatic pressure is made under the pressure of 150-250MPa with the tungsten powder of 0.8-2.5 micron size of Fisher particle size and the percentage of 0.1-1.4% doped with the mass of lanthanum oxide. The cold isostatic press is made. The cold isostatic blank is put into the medium frequency furnace to get the sintered tungsten bar under the atmosphere of hydrogen. The diameter of the rod is 20-150mm, and the highest in the sintering process. When the temperature is 1900-2300°C, the density of the sintered tungsten bar billet is not less than 90% of theoretical density, and then passes through the grinding outer circle.

(2) Through the processing of at least one kind of sintered tungsten bar in the fast forging machine, air hammer and rotary hammer machine, the rare earth lanthanum doped tungsten rods are forged to the theoretical density of the diameter of 15-130mm and the density of the rare earth doped tungsten rods is less than 95%.

(3) The rare-earth doped tungsten rod after forging has been worn out of the outer circle, grinding to the diameter 10-120mm, removing the surface oxide and defects to form the polished tungsten rod. Using the deep hole drilling method to drill the polished tungsten rod, the diameter of the hole is greater than 4mm, the diameter ratio of the hole is greater than 10, and the rare earth lanthanum doped tungsten tube is made.

By doping rare earth lanthanum, the prepared tungsten tubes have good temperature resistance and creep resistance at high temperature, and have good machinability at normal temperature. It is especially suitable for making tungsten tubes with large diameter ratio. The ductile brittle transition temperature of tungsten tube has been obviously reduced, and it is not easy to crack when it is installed and used at room temperature.

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