Tungsten crucible is widely used in the production of LED chips because of its low coefficient of thermal expansion, good high-temperature resistance, and conductivity. However, because pure tungsten is easy to oxidize at high temperatures, the service life of the crucible is short. In view of the above shortcomings, the researchers said that an appropriate amount of rare earth elements can be added during its production, so as to improve the durability of products and reduce production costs.
The specific preparation steps of rare earth tungsten crucible are as follows:
(1) Manufacture rare earth tungsten alloy powder, weigh 94.6% ~ 96.8% ammonium para tungstate and 3.2% ~ 5.4% lanthanum oxide according to the mass percentage, add ammonium para tungstate into the reactor and heat it to 70 ℃ ~ 90 ℃, then add lanthanum oxide, continue heating and stirring until it becomes a dry composite powder, and then reduce at high temperature under the protection of hydrogen to obtain rare earth tungsten alloy powder;
(2) Prepare the rare earth tungsten crucible blank, put the rare earth tungsten powder obtained in step (1) into the rubber mold, and then put it into the isostatic press for high-pressure pressing to obtain the raw blank, and then conduct pre sintering. The pre sintering temperature is 1100 ℃ ~ 1250 ℃, and the pre sintering time is 30min ~ 45min to prepare the fine blank of the rare earth tungsten alloy crucible;
(3) Preparation of finished products, The refined blank of the rare earth tungsten alloy crucible in step (2) is sintered at high temperature in a medium frequency induction furnace, The high-temperature sintering temperature is 2350 ℃ ~ 2420 ℃, The high-temperature sintering time is 12h, Semi-finished products of rare earth tungsten alloy crucible were prepared, Then the surface finish and precision processing shall be carried out, The finished product of rare earth tungsten alloy crucible can be obtained.
The highlight of the production technology is that the lanthanum oxide in the tungsten alloy can be evenly dispersed and distributed, the grain of the material is refined, and the mechanical properties of the tungsten alloy can be significantly improved, so as to enhance the plasticity and crack resistance tensile strength of the tungsten alloy.
