Vacuum brazing furnace vacuum control technology details

Vacuum brazing is a welding process carried out in a vacuum environment, mainly used to connect high-precision, high-strength metal materials. Vacuum brazing furnace as the core equipment, its vacuum control technology directly affects the welding quality and process stability. In this paper, we will analyze in detail from the definition of vacuum degree, control principle, key technology and common problems.

---

First, the definition and importance of vacuum

Vacuum is the vacuum furnace gas pressure, usually expressed in Pa (Pascal) or Torr (Torr). Vacuum brazing furnace vacuum range is generally between 10-³ Pa to 10-⁵ Pa, the specific value depends on the material properties and process requirements.

The importance of vacuum is reflected in the following aspects:

1. preventing oxidation: vacuum environment can effectively avoid metal materials reacting with oxygen at high temperatures, thus preventing oxidation and contamination.

2. Improvement of welding quality: High vacuum helps to remove impurities and gases from the material surface, ensuring the cleanliness and strength of welded joints.

3. Controlling process parameters: vacuum is a key factor affecting heating rate, cooling rate and material fluidity.

---.

Second, the basic principle of vacuum control

Vacuum brazing furnace vacuum control is mainly realized through the vacuum pump system, sealing structure and vacuum measuring device. Its basic principles include:

1. vacuum pumping process: through mechanical pumps, Roots pumps and molecular pumps and other multi-stage vacuum pump system, the furnace gas is gradually discharged to achieve the target vacuum level.

2. vacuum monitoring: using vacuum gauge (such as thermocouple vacuum gauge, ionization vacuum gauge) real-time monitoring of the pressure in the furnace, and feedback data to the control system.

3. pressure adjustment: according to the process requirements, through the adjustment of vacuum pump operation status or the introduction of inert gas (such as argon, nitrogen) to accurately control the vacuum degree.

---

Third, the key technology of vacuum degree control

1. Multi-stage vacuum pump system

- Mechanical pump: used for initial vacuum pumping to reduce the pressure inside the furnace from atmospheric pressure to 10-¹ Pa.

- Roots pump: used as an intermediate stage pump to further reduce the pressure to 10-² Pa.

- Molecular pumps: for the high vacuum stage to reduce the pressure to below 10-³ Pa.

- The synergistic work of the multi-stage pumping system achieves high vacuum levels efficiently and stably.

2. Sealing technology

- Static seals: metal seals or Viton seals are used to ensure the gas tightness of the furnace at high temperatures.

- Dynamic sealing: For sealing of rotating or moving parts, such as shaft seals and magnetic fluid seals.

3. Vacuum measurement and feedback control

- Vacuum gauge selection: select the appropriate vacuum gauge according to the vacuum range, such as thermocouple vacuum gauge for low vacuum, ionization vacuum gauge for high vacuum.

- Feedback control: connect the vacuum gauge data with the control system to realize the automatic adjustment of vacuum degree.

4. Gas purification and introduction

- Gas purification: Remove water and impurities in the gas by molecular sieve or cold trap to ensure the high purity of the vacuum environment.

- Gas introduction: introduce inert gas when needed to regulate the pressure in the furnace or improve the welding environment.

5. Synergistic control of temperature and vacuum

- Vacuum level is closely related to temperature. High temperature may lead to material outgassing and affect the vacuum level. Therefore, synergistic control of temperature and vacuum level needs to be realized to ensure process stability.

---

IV. Common Problems and Solutions

1. Insufficient vacuum

- Cause: Poor sealing, degradation of vacuum pump performance or gas leakage.

- Solution: Check the sealing structure, replace the damaged sealing ring; maintain or replace the vacuum pump; use helium mass spectrometer leak detector to detect the leakage point.

2. Vacuum fluctuation

- Cause: unstable operation of vacuum pump or uneven introduction of gas.

- Solution: Optimize the operating parameters of the vacuum pump; use flow meter to precisely control the amount of gas introduction.

3. material outgassing

- Cause: The material releases gas under high temperature, which leads to the decrease of vacuum degree.

- Solution: Extend the pre-evacuation time, or carry out sufficient degassing in the low temperature stage.

4. Vacuum gauge error

- Cause: Inaccurate calibration of the vacuum gauge or environmental influences.

- Solution: calibrate the vacuum gauge regularly to ensure the measurement accuracy; avoid using the vacuum gauge in strong magnetic field or high temperature environment.

---

V. Future Development Trends

1. Intelligent control: introduce artificial intelligence and machine learning technology to realize adaptive control of vacuum level and fault prediction.

2. High efficiency and energy saving: develop low energy consumption and high efficiency vacuum pumping system to reduce equipment operation cost.

3. high purity environment: through gas purification and material optimization, further improve the purity of the vacuum environment to meet the needs of high-end material welding.

4. integrated design: integrate vacuum control with temperature and atmosphere control to improve the comprehensive performance of the equipment.

---

VI. Summarize

The vacuum control technology of vacuum brazing furnace is the key link to ensure the welding quality. Through the comprehensive application of multi-stage vacuum pump system, sealing technology, vacuum measurement and feedback control and other technologies, a high-precision, high-stability vacuum environment can be realized. In the future, with the development of intelligence, energy saving and integration, the vacuum degree control technology will be further upgraded to provide stronger support for the application of vacuum brazing process.