Quartz tube vacuum sealing machineIt is a specialized equipment that integrates vacuum extraction and high-temperature melting technology. With the high temperature resistance and strong chemical stability of quartz material, combined with the isolation and protection advantages of vacuum environment, it achieves the sealed packaging of samples. Its core value lies in providing a long-term storage or reaction environment of "vacuum or inert gas atmosphere" for sensitive samples, which is widely used in materials science, chemical synthesis, electronic devices and other fields. This article will deeply analyze the working principle of the equipment, and combine it with practical scenarios to sort out its application directions, providing theoretical support for equipment selection and use.
Core working principle: collaborative mechanism of vacuum and high temperature
Quartz tube vacuum sealing machineThe working logic revolves around three core steps: vacuum environment construction, high-temperature melting and sealing, cooling and solidification. Through the precise coordination of the vacuum system and heating system, high airtightness packaging of quartz tubes is achieved. The core principle can be broken down into two parts: vacuum extraction principle and high-temperature sealing principle, which work together to ensure the quality of sealing.
（1） Working principle of vacuum system: creating low oxygen/anaerobic environment
The vacuum system is the "environmental protection core" of the equipment, mainly composed of vacuum pumps (oil type vacuum pumps, dry vacuum pumps), vacuum gauges, vacuum pipelines, and sealing components. Its core function is to extract air and volatile impurities from the quartz tube, and build a stable low vacuum or high vacuum environment. The principle is as follows:
Vacuum gradient extraction mechanism: The equipment usually adopts a two-stage extraction mode of "coarse extraction fine extraction". Firstly, the air pressure inside the quartz tube is rapidly reduced by a rough vacuum pump (or the rough pumping stage of the main pump), reducing the air concentration from atmospheric pressure (101.3kPa) to below 10Pa and removing most of the macroscopic air; Then switch to fine pumping mode (such as diffusion pump assisted or main pump high-precision operation), further increase the vacuum degree to 10 ⁻ Pa or even 10 ⁻ Pa level, efficiently remove small bubbles and volatile components. This gradient extraction method can ensure vacuum extraction efficiency and achieve high vacuum accuracy, meeting the requirements of different experiments for vacuum degree.
Sealing and pressure control principle: During the vacuum pumping process, the quartz tube is tightly connected to the vacuum pipeline through a sealing gasket (made of vacuum resistant materials such as fluororubber and silicone rubber) to prevent external air from flowing back. When the vacuum degree reaches the preset value, the system closes the vacuum valve and enters the pressure holding stage, monitoring the pressure changes in real time through the vacuum gauge. If the rate of vacuum degree decrease during the pressure holding period is ≤ 0.1Pa/h, it indicates that the system is well sealed and has no leakage points; If the pressure suddenly rises, a leak alarm will be triggered, prompting the inspection of the sealing of the interface or quartz tube itself.
Inert gas replacement principle (optional function): For samples that are prone to oxidation or require a specific gas atmosphere, the equipment can be equipped with an inert gas replacement system. The principle is to introduce inert gases such as argon and nitrogen into the quartz tube after vacuuming. After the pressure inside the tube returns to a slightly positive pressure (0.01-0.05MPa), the vacuum is evacuated again, repeating 2-3 times to reduce the residual oxygen content in the tube to below 10ppm, forming an inert gas protective atmosphere to prevent sample oxidation and deterioration.
（2） Heating sealing principle: quartz tube melting and sealing forming
The heating system is the "sealing execution core" of the equipment, and the mainstream heating methods are divided into high-frequency induction heating and flame heating. Its core principle is to use high temperature to melt the quartz tube to be sealed, and achieve a closed connection through mechanical shaping. The specific mechanism is as follows:
High frequency induction heating principle (mainstream technology): The equipment generates an alternating magnetic field through a high-frequency induction coil. When the quartz tube to be sealed is in the magnetic field, eddy current effect is generated inside the tube body, forming Joule heat, causing the local temperature to quickly rise to 1700-1800 ℃ (the melting temperature of quartz glass). This heating method has the advantages of fast heating speed (reaching melting temperature in 5-10 seconds), concentrated heating area (precise control of melting range ± 2mm), and good temperature uniformity. It can effectively avoid cracking of quartz tubes caused by local overheating and is suitable for high-precision sealing scenarios.
Flame heating principle (traditional technology): combustible gases (such as hydrogen+oxygen, acetylene+oxygen) are burned to produce high-temperature flames, which are directly sprayed onto the sealing part of the quartz tube to melt the tube body. The advantages of flame heating are low equipment cost and adaptability to large-diameter quartz tubes (inner diameter ≥ 50mm), but the uniformity of heating temperature is poor and it is easily affected by airflow, resulting in irregular melting areas. It is suitable for scenarios with low sealing accuracy requirements.
Melting molding and sealing principle: Regardless of the heating method used, when the quartz tube reaches a molten state, axial pressure is slowly applied through the clamping system of the equipment, causing the quartz glass at the molten part to fuse with each other and form a dense sealing surface. Subsequently, gradient cooling (slowly lowering from the melting temperature to room temperature, with a cooling rate controlled at 5-10 ℃/min) is used to avoid cracks in the quartz tube due to thermal stress, ensuring the mechanical strength and airtightness of the sealing surface. After sealing, the pressure resistance strength of the sealed area can reach 1-2MPa, and the vacuum leakage rate is ≤ 10 ⁻⁹ Pa · m ³/s, meeting the long-term vacuum storage requirements.