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Vacuum brazing of gemstones and metals

With technological advancements and industrial development, the bonding of sapphire and metal is becoming increasingly widespread. However, due to the significant differences in physical and chemical properties between sapphire and metal, traditional welding methods often struggle to achieve an effective bond. Therefore, vacuum brazing technology has emerged, offering a new solution for bonding sapphire and metal.

Vacuum brazing is a brazing method performed in a vacuum environment. By excluding oxygen and other impurities during the welding process, vacuum brazing effectively prevents oxidation and contamination of the weld joint, thereby improving weld quality and reliability. Vacuum brazing offers significant advantages for bonding sapphire to metal.

First, the vacuum environment effectively protects sapphire from oxidation and contamination, preserving its original optical and mechanical properties. Second, vacuum brazing achieves a secure bond between sapphire and metal, improving bond strength and stability. Finally, vacuum brazing allows for precise weld control, meeting the demands of high-precision machining.

The Technical Principles of Vacuum Brazing of Sapphire to Metal

The principle of vacuum brazing of sapphire to metal is primarily based on physical and chemical processes in a vacuum environment. In a vacuum environment, oxidation and contamination of the weld joint are effectively controlled, thereby achieving a strong bond between the sapphire and metal.
Specifically, during the vacuum brazing process, the sapphire and metal surfaces to be welded must first be cleaned to remove surface oil, oxides, and other impurities. The cleaned sapphire and metal are then placed in a vacuum brazing machine, and air and other impurities are removed from the machine to create a high vacuum brazing environment.
In a vacuum environment, the sapphire and metal are heated to a molten state and then welded under a certain pressure. Because the vacuum environment eliminates the interference of oxygen and other impurities, oxidation and contamination of the weld joint are effectively controlled, thus achieving a strong bond between the sapphire and metal. Furthermore, precise control of welding parameters such as temperature, time, and pressure further ensures weld quality and reliability.

The vacuum brazing process for sapphire and metal includes the following steps:

1. Preparation: Select the appropriate sapphire and silver-copper-titanium brazing material and perform necessary pretreatment, such as cutting, polishing, and cleaning. Ensure that the weld area is free of oil, oxides, and other impurities.
2. Vacuum Environment Creation: Place the cleaned sapphire and metal in the vacuum brazing equipment and remove air and other impurities to create a high vacuum brazing environment. Vacuum equipment such as mechanical pumps and diffusion pumps are typically used to achieve this high vacuum.
3. Heating and Melting: Heat is applied to the sapphire and metal in a vacuum environment until they reach a molten state. Heating methods include resistance heating, induction heating, or radiation heating. Controlling the heating temperature and duration is crucial to ensure the quality and reliability of the weld joint.
4. Welding and Cooling: After the sapphire and metal have reached a molten state, welding is performed. A certain amount of pressure is applied to tightly bond the molten metal to the sapphire. After welding, the cooling rate must be controlled to prevent defects such as cracks and deformation in the weld joint. 5. Post-processing and testing: The sapphire-metal bond undergoes post-processing, such as grinding, polishing, and cleaning. Necessary testing, such as visual inspection, mechanical and optical performance testing, is also performed to ensure weld quality and reliability.

Key Technologies and Challenges of Vacuum Brazing of Sapphire to Metal

While vacuum brazing of sapphire to metal offers significant advantages, it also faces several key technical and challenges in practical application.
Quality Control of Welded Joints: Due to the significant differences in physical and chemical properties between sapphire and metal, quality control of welded joints is a key technology. Precise control of parameters such as welding temperature, time, and pressure is required to ensure the strength and stability of the welded joint.
Control and Maintenance of Vacuum: Vacuum is a critical parameter in the vacuum brazing process. Precise control of vacuum levels and measures to maintain a stable vacuum environment are necessary to prevent oxidation and contamination during welding.

Control and Elimination of Welding Stress: During welding, welding stress is easily generated due to factors such as temperature gradients and differences in material properties. Measures must be taken to control and eliminate welding stress to prevent defects such as cracks and deformation in the welded joint.