What are the processes and applications of vacuum furnaces?
Vacuum furnace process
1. **Vacuuming process**:
- **Pre-vacuuming**: Before heating, the vacuum pump must be started to extract the air and other gases in the furnace to reduce the pressure in the furnace to a certain level, usually to a high vacuum or ultra-high vacuum state. For example, for general vacuum heat treatment, the pressure may need to be pumped to a range of 10⁻² - 10⁻³Pa; and for some processes that require extremely high vacuum, such as electron beam melting, the vacuum may need to reach 10⁻⁴Pa or even higher.
- **Maintaining vacuum**: During the entire heating, insulation and cooling process, the vacuum pump needs to work continuously or intermittently to maintain the vacuum state in the furnace. Because the material will release gas during the heating process, such as adsorbed gas, volatiles of the material itself, etc., if it is not extracted in time, it will affect the vacuum and process effect.
2. **Heating process**:
- **Resistance heating**: By passing current through heating elements such as resistance wires or resistance belts, it generates heat, thereby heating the workpiece in the furnace. This heating method has good temperature uniformity and is relatively simple to control. It is often used in medium and low temperature vacuum furnaces, such as vacuum annealing furnaces, vacuum tempering furnaces, etc.
- **Induction heating**: Using the principle of electromagnetic induction, an induced current is generated inside the workpiece to make it heat itself. Induction heating has the advantages of fast heating speed, high efficiency, and concentrated energy. It is suitable for processes with high heating speed requirements, such as vacuum melting and vacuum quenching.
- **Electron beam heating**: In a high vacuum environment, a high-speed electron beam emitted by an electron gun is used to hit the surface of the workpiece, converting the kinetic energy of the electrons into thermal energy, thereby heating the workpiece. The energy density of electron beam heating is extremely high, and the workpiece can be heated to a very high temperature in a short time. It is often used in metal smelting, purification and high-temperature heat treatment.
- **Plasma heating**: By generating plasma in the furnace, the high temperature and activity of the plasma are used to heat the workpiece. Plasma heating can be carried out at a lower gas pressure, which can achieve rapid and uniform heating, and has advantages for the treatment of some special materials.
3. **Cooling process**:
- **Air cooling**: Inert gas, such as nitrogen, argon, etc., is introduced into the vacuum furnace, and the heat of the workpiece is taken away by the flow of gas to achieve cooling. The cooling speed of air cooling is relatively slow, but it can prevent the workpiece from oxidizing during the cooling process. For some workpieces that do not require high cooling speed but have high surface quality requirements, such as precision parts and molds, air cooling is often used.
- **Water cooling**: Water cooling pipes or water cooling jackets are set in certain parts of the furnace body or around the workpiece to absorb heat through the circulation of water to achieve rapid cooling. Water cooling has a fast cooling speed and high efficiency, but it is necessary to prevent water leakage and the influence on the vacuum degree in the furnace. In some processes that require high cooling speed, such as vacuum quenching, a combination of water cooling and air cooling is often used.
4. **Process parameter control**:
- **Temperature control**: Accurate control of heating temperature is the key to vacuum furnace technology. Temperature sensors such as thermocouples and thermal resistors are usually used to monitor the temperature in the furnace in real time, and the heating power is adjusted through the temperature control system to keep the temperature within the set range. For some processes that require extremely high temperature accuracy, technologies such as temperature compensation and temperature uniformity correction are also required.
- **Time control**: including heating time, holding time and cooling time. Different processes have different time requirements, which need to be determined according to specific materials, workpiece sizes and process requirements. For example, in the vacuum sintering process, the length of the holding time will directly affect the density and performance of the sintered body; in the vacuum quenching process, the control of the cooling time is crucial to the hardness and organizational properties of the workpiece.
- **Pressure control**: In addition to controlling the vacuum degree in the furnace, in some special processes, the gas pressure needs to be controlled. For example, in the vacuum carburizing process, a certain amount of carburizing gas needs to be introduced into the furnace, and the gas pressure and flow rate need to be controlled to achieve carburizing treatment of the workpiece.
**Application of vacuum furnace**
1. **Heat treatment of metal materials**:
- **Vacuum quenching**: It can make the metal material cool quickly after heating to obtain a high-hardness, high-strength martensitic structure, while reducing the deformation and cracking of the workpiece. For example, vacuum furnaces are often used for quenching treatment of automotive parts, molds, cutting tools, etc.
- **Vacuum annealing**: used to eliminate stress, improve organizational structure and plasticity of metal materials. For example, in the electronics industry, vacuum annealing of semiconductor materials can improve their purity and performance.
- **Vacuum tempering**: Tempering after quenching can reduce the brittleness of the workpiece and improve its toughness and comprehensive mechanical properties. Commonly used for heat treatment of various mechanical parts.
2. **Melt and cast of metal materials**:
- **Vacuum melting**: can effectively remove impurities, gases, etc. in the metal and improve the purity and quality of the metal. For example, in the aerospace field, vacuum furnaces are usually used for the melting of some high-performance alloy materials.
- **Vacuum casting**: can avoid oxidation and air absorption of metal during the pouring process, and improve the quality and performance of castings. For example, vacuum casting technology is used in the casting of some precision castings, aircraft engine blades, etc.
3. **Powder metallurgy**:
- **Vacuum sintering**: metal powder or ceramic powder is heated and sintered in a vacuum environment to combine the powder particles with each other to form a dense material. Vacuum sintering can improve the density, strength and hardness of materials, and is widely used in the production of cemented carbide, ceramic materials, magnetic materials, etc.
- **Powder forging**: First, pre-sinter the metal powder in a vacuum furnace, and then forge it at high temperature to make the material's structure denser and its performance more excellent.
4. **Preparation and processing of semiconductor materials**:
- **Annealing of semiconductor wafers**: It can repair the defects of the wafers produced during the processing and improve the electrical properties and stability of the wafers.
- **Deposition of semiconductor thin films**: Processes such as physical vapor deposition (PVD) and chemical vapor deposition (CVD) can improve the quality and purity of the film in a vacuum environment.
5. **Firing of ceramic materials**:
- **Firing of structural ceramics**: It can make ceramic materials have high hardness, high strength, high temperature resistance and other properties, and is used to manufacture ceramic tools, ceramic bearings, ceramic engine parts, etc.
- **Firing of electronic ceramics**: It is used to produce electronic ceramic components such as capacitor ceramics, piezoelectric ceramics, and magnetic ceramics. The vacuum environment can ensure the electrical properties and stability of ceramic materials.
6. **Vacuum brazing**: Brazing in a vacuum environment can avoid metal oxidation and joint contamination during the brazing process, and improve the quality and reliability of the brazed joint. It is widely used in the connection of parts in the fields of aerospace, electronics, machinery, etc.
7. **Surface treatment of materials**:
- **Ion implantation**: In a vacuum environment, ions are accelerated and injected into the surface of the material to change the surface properties of the material, such as improving hardness, wear resistance, corrosion resistance, etc.
- **Vacuum coating**: By evaporating or sputtering metals, ceramics and other materials in a vacuum environment, a thin film is formed on the surface of the workpiece for decoration, corrosion resistance, wear resistance and other purposes.
English
简体中文
Русский язык
Français
日本語
한국어
Português
Español
Position:
E-mail:
Tell:
Whatapp:
Address:Room 1505, Building 9, No. 26 Dongqing Street, Zhengzhou High-tech Industrial Development Zone
Website navigation
