Molybdenum crucibles are suitable for glass melting, especially in high temperature, high purity and special process requirements. The following is a detailed description of the applicability principle, technical advantages and application scenarios:
- Applicability principle
High temperature resistance
molybdenum is as high as 2610℃. The molybdenum crucible can work stably at high temperatures above 2000℃, meeting the melting requirements of high-melting-point glasses such as quartz glass (melting point is about 1713℃).
During the glass melting process, the molybdenum crucible can withstand high temperatures for a long time without deformation or melting, ensuring process stability.
Chemical stability
Molybdenum does not chemically react with glass melts (such as silicates, borates, etc.) at high temperatures, thus avoiding the introduction of impurities and ensuring the purity and optical properties of the glass.
Especially in the fields of optical glass, optical fiber preforms, etc. which have extremely high requirements on purity, the chemical inertness of molybdenum crucible is very important.
Thermal conductivity
Molybdenum has high thermal conductivity (about 138 W/(m·K)), which can conduct heat quickly and evenly, reduce the temperature gradient in the glass melt, and avoid glass defects (such as bubbles and streaks) caused by local overheating.
- Technical advantages
High purity guarantee
Molybdenum crucibles are made of high-purity molybdenum powder (≥99.95%) to avoid metal impurities contaminating the glass melt and meet the purity requirements of high-end glass (such as optical glass and semiconductor glass).
Thermal shock resistance
Molybdenum ‘s low thermal expansion coefficient (about 5.5×10 ⁻⁶ / ℃) makes it excellent in thermal shock resistance during high-temperature melting and cooling, reducing the risk of cracking due to thermal stress.
Mechanical strength
Molybdenum crucible has high strength and hardness, can withstand the mechanical impact and pressure in the glass melting process, and prolong its service life.
- Application Scenarios
Quartz glass melting
The melting of quartz glass (melting point 1713℃) needs to be carried out at a high temperature above 2000℃, and molybdenum crucible is the core container in this field.
For example, China’s quartz glass production requires about 25 molybdenum crucibles and consumes about 6 tons of molybdenum materials each year.
Optical glass manufacturing
In the production of optical glass (such as borosilicate glass), molybdenum crucibles are used to melt high- purity raw materials to ensure the light transmittance and uniformity of the glass.
Special glass research and development
In the research and development of special glasses such as optical fiber preforms and semiconductor glass, molybdenum crucibles provide a high-temperature, pure melting environment to promote material innovation.
- Cases and Data Support
Quartz glass melting: Molybdenum crucible is used as the core container in the quartz glass melting furnace. The annual demand is stable, which verifies its reliability in high-temperature glass melting.
Purity of optical glass: The impurity content of optical glass melted in molybdenum crucible can be controlled at ppm level to meet the needs of high-end applications.
thermal shock performance: Compared with graphite crucibles, the cracking rate of molybdenum crucibles during high-temperature rapid cooling is reduced by more than 50%, significantly improving production efficiency.
- Notes
Oxidation protection
In a high-temperature oxidizing environment, volatile MoO₃ is easily generated on the molybdenum surface, resulting in material loss. It needs to be used under vacuum or inert gas (such as Ar) protection.
Surface coating technology (such as Mo₂C and ZrO₂ coating) can effectively delay oxidation.
Cost and lifespan
Molybdenum crucibles cost more than traditional crucibles (such as graphite, alumina), but their long life (about 30-80 heats) and low maintenance cost make them more economical in high-end applications.
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