Why Is Molybdenum Sheet Chosen as Reflective Screens in Vacuum Furnaces?

A vacuum furnace is a device that performs high-temperature heat treatment or material processing in a high-vacuum environment, widely used in applications such as sapphire crystal growth, metal heat treatment, and ceramic sintering. Within the vacuum furnace, the reflective screen is a critical component, designed to reduce heat loss, improve thermal efficiency, and protect the furnace structure. Due to its excellent physical and chemical properties, molybdenum sheet is the preferred material for vacuum furnace reflective screens.

Molybdenum has a melting point of 2,623°C, far exceeding that of many common metals like iron and nickel, enabling it to maintain structural stability and mechanical strength under extreme high temperatures. In high-temperature vacuum environments, molybdenum sheet resists significant softening, deformation, or melting, enduring prolonged thermal radiation and thermal shock to ensure the reliability and longevity of the reflective screen. In contrast, ordinary metals may fail rapidly under such conditions, leading to deformation or damage of the reflective screen, which could disrupt the uniformity of the furnace's heat field.

Molybdenum sheet exhibits good chemical stability in vacuum or reducing atmospheres, avoiding chemical reactions with residual gases or protective gases within the furnace, as well as with processed materials. This chemical inertness prevents the formation of oxides or other compounds on the reflective screen's surface, avoiding the introduction of impurities into the processed materials and thus ensuring product quality.

The primary function of the reflective screen is to reduce heat loss by reflecting thermal radiation, thereby enhancing the vacuum furnace's thermal efficiency. Molybdenum sheet possesses high thermal reflectivity, effectively reflecting infrared radiation back into the heating zone, minimizing heat transfer to the furnace walls, reducing energy consumption, and improving temperature uniformity. The reflectivity of molybdenum sheet can be further enhanced through polishing, amplifying their thermal shielding effect. Additionally, molybdenum's low thermal conductivity helps reduce heat loss through conduction, making it highly effective as a reflective screen in high-temperature environments.

Molybdenum sheet offers excellent ductility and processability, allowing it to be shaped into various complex forms through rolling, cutting, stamping, and welding to meet the design requirements of different vacuum furnaces. Whether circular, cylindrical reflective screens, or multi-layered structures, molybdenum sheet can be precisely machined to fit accordingly.

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