Preparation of rare earth tungsten alloy crucible
Tungsten crucible is widely used in the production of LED wafers because of its low thermal expansion coefficient, good high temperature resistance and electrical conductivity. However, because pure tungsten is easy to oxidize at high temperature, the service life of tungsten crucible is short. In view of the above shortcomings, the researchers suggest that a proper amount of rare earth elements can be added to the production of tungsten crucible to improve the durability of the product and reduce the production cost.
The specific preparation steps of the rare earth tungsten alloy crucible are as follows:
(1) The rare earth tungsten alloy powder was prepared by weighing ammonium paratungstate (94.6%-96.8%) and lanthanum oxide (3.2%-5.4%) according to the mass ratio. The ammonium paratungstate was added into the reaction reactor and heated to 70℃ ~ 90℃, and then the lanthanum oxide was added, and the powder was heated and stirred until it became a dry composite powder. Then the rare earth tungsten alloy powder was reduced under the protection of hydrogen at high temperature.
(2) To prepare the rare earth tungsten alloy crucible blank, load the rare earth tungsten alloy powder obtained in step (1) into the glue mold, and then load it into the isostatic press for high pressure pressing to obtain the rare earth tungsten alloy crucible blank. After the pre-sintering, the pre-sintering temperature is 1100℃ ~ 1250℃, and the pre-sintering time is 30min ~ 45min, the rare earth tungsten alloy crucible fine blank is prepared.
(3) To prepare the finished product, the rare earth tungsten alloy crucible fine stock of step (2) was sintered at high temperature in the medium frequency induction furnace. The high temperature sintering temperature was 2350℃ ~ 2420℃, and the high temperature sintering time was 12h. Then the semi-finished rare earth tungsten alloy crucible was prepared.
The highlight of this production technology is that the lanthanum oxide in tungsten alloy can be uniformly dispersed, refine the grain of the material, and significantly improve the mechanical properties of tungsten alloy, thus enhancing the plasticity and fission tensile strength of tungsten alloy.
