Like evaporative tungsten boat, tungsten crucible is also a typical product of refractory metal tungsten. It uses metal tungsten powder as the main raw material, and is a high temperature resistant vessel. The tungsten content is generally higher than 99.95%, generally cylindrical shape, with diameter between 10mm and 500mm, height between 10mm and 750mm, wall thickness between 8mm and 20mm.
Tungsten Production Process
Tungsten powder – Sieving – Combined batch – Isostatic pressing – Rough turning – Medium frequency sintering – Fine turning – Packaging.
Applications of tungsten crucible
Since the melting point of tungsten is as high as 3410°C, tungsten crucibles are widely used as core vessels in industrial furnaces such as sapphire single crystal growth furnaces, quartz glass melting furnaces, and rare earth smelting furnaces, which are generally used in an operating temperature environment of 2000°C or higher. Especially for sapphire single crystal growth furnaces, tungsten crucibles with high purity, high density, no internal cracks, precise size, smooth inner and outer walls, etc. play a key role in the success rate of seeding crystals, quality control of pulling crystals, de-crystallization sticking pots and service life in the sapphire crystal growth process.
From the perspective of physical and chemical properties, the characteristics of tungsten crucible include high specific gravity, high melting point, high boiling point, low steam pressure, small evaporation speed, low thermal expansion coefficient, corrosion resistance, wear resistance, good thermal conductivity, etc. Note: According to the different production process, the tungsten crucible can be divided into forging forming, sintering forming, welding forming, stamping forming, rotary forming, etc., where the density of forging forming and sintering forming is greater than 19.35g/cm3 and 18.5g/cm3, respectively; adding a certain amount of rare earth elements to the pure tungsten crucible can improve the oxidation resistance of the crucible, and then prolong the service life of the product.
From the perspective of production methods, the preparation steps of tungsten crucible include ingredient mixing, isostatic pressing, shaping, sintering and finishing. The ingredients adopt four different tungsten powder in 1.0~5.0um range; isostatic pressure is about 200MPa and pressure retention is about 7 minutes; sintering temperature is about 2300°C and sintering time is about 7 hours.
From the point of application, tungsten crucible is widely used in rare earth smelting, quartz glass, electronic spraying, crystal growth industry, mainly used as rare earth metal smelting furnace, quartz glass smelting furnace, induction furnace heating body, single crystal furnace high temperature container, sapphire single crystal growth furnace, high temperature vacuum furnace industrial furnace, its working temperature is generally above 2000°C. Note: In the growth process of sapphire crystal, the tungsten crucible should have the characteristics of no internal cracks, accurate size, and smooth and clean inner and external walls.