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Tungsten crucible is one of Tungsten metal products. It is mainly divided into sintering forming (applied to powder metallurgy technology), stamping forming, and spinning. Using tungsten bar turning processing forming (generally small size), welding forming a variety of, using pure tungsten plate, tungsten piece and pure tungsten bar by the corresponding process processing. Tungsten crucible can be used in vacuum inert gas below 2600 degrees.
Material: Tungsten (W≥99.95%)
Density: ≥18.5g/cm3
The highest application temperature environment: 2400℃
Supply Situation | Dimensions | Tolerance | ||
Diameter(mm) | Height(mm) | Diameter(mm) | Height(mm) | |
Sintering | 10-500 | 10-750 | ±5 | ±5 |
Forging | 10-100 | 10-120 | ±1 | ±2 |
Sintering and Machining | 100-550 | 10-700 | ±0.5 | ±1 |
Because the melting point of tungsten is as high as 3410℃, tungsten crucible is widely used in the core container of sapphire single crystal growth furnace, quartz glass melting furnace, rare earth smelting furnace and other industrial furnaces, and its working temperature environment is generally above 2000℃. Especially for sapphire single crystal growth furnace, tungsten crucible with high purity, high density, no internal crack, precise size, bright and clean inside and outside wall, etc. plays a key role in the success rate of seed crystal, quality control of crystal drawing, decrystallizing and sticking pot and service life of sapphire crystal growth process.
High Melting Point: Tungsten has one of the highest melting points of all metals, exceeding 3,400 degrees Celsius (6,152 degrees Fahrenheit).
Excellent Thermal Stability: Tungsten crucibles exhibit excellent thermal stability, maintaining their structural integrity and dimensional stability even at high temperatures. This ensures consistent performance and reliable containment of molten materials during the melting process.
Chemical Inertness: Tungsten is highly resistant to chemical attack and corrosion, making tungsten crucibles suitable for use with reactive metals and alloys. They can withstand the corrosive effects of molten metals and harsh chemical environments without degradation or contamination of the melt.
Uniform Heating: Tungsten crucibles have excellent thermal conductivity, allowing for efficient and uniform heating of the melt. This promotes uniform melting and mixing of alloying elements, resulting in high-quality and homogeneous castings.
Longevity and Durability: Tungsten crucibles are known for their durability and long service life, even under harsh operating conditions. They resist mechanical wear and thermal shock, ensuring reliable performance over multiple heating and cooling cycles.
Tungsten crucibles are available in various shapes and sizes to suit different melting applications, including cylindrical, conical, and custom-designed configurations. They are used in a wide range of processes, including vacuum arc melting, induction melting, electron beam melting, and sintering of powders.
Material Preparation:
Tungsten crucible materials primarily consist of tungsten powder. Due to the high hardness of tungsten products at room temperature, there is no need for mechanical processing after sintering. Thus, there are no special requirements for tungsten powder. However, to enhance the high-temperature strength and corrosion resistance of tungsten crucibles, approximately 8% molybdenum powder is often added for solid solution strengthening. The sifted tungsten and molybdenum are mixed in the appropriate proportion to achieve the desired composition.
Tungsten Crucible Molding:
Mold Design: The design of the tungsten crucible mold considers parameters such as the shrinkage rate after sintering, which is approximately 12% axially and 13% radially. External molds use soft materials, while internal molds use steel. The steel mold has a thickness of about 5 mm and a taper of approximately 0.4%. The mold should have a clean wall to facilitate ejection, and a rough side should be welded to the crossbeam for hoisting. Latex ring cork seals are applied on both ends.
Molding and Loading: After preparing the mold, the charging process requires uniform thickness to ensure consistent wall thickness after sintering. Care must be taken during lifting to prevent any decrease in pressure. Cold isostatic pressing machines are used for forming, with pressure controlled between 200 to 220 MPa for 3 minutes. Pressure is relieved in two stages to prevent cracking caused by rapid unloading.
Tungsten Crucible Sintering:
The sintering of tungsten crucibles typically involves three sintering processes:
First Sintering: The compact is placed in an induction furnace with a graphite circular plate underneath. The temperature is raised to 1500°C and maintained for 5 hours for temperature testing and insulation.
Second Sintering: After the first sintering, the crucible is hoisted out and placed back into the furnace at a temperature of 1700 to 1800°C for 5 hours, followed by 7 hours of cooling.
Third Sintering: In the third sintering, the crucible is placed back into the furnace with the induction coil, and additional refractory material is added. The temperature is held at around 100°C for 3 hours to improve the uniformity of the alloy composition. After cooling, the crucible is hoisted out, and the upper and lower ends are exchanged before being put into use.
Purity: W≥99.95%;
Density: ≥18.5g/cm3;
The highest application temperature environment: 2400℃.
