Technical improvement of vacuum sintering furnace

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Composition System of Vacuum Sintering Furnace
Vacuum sintering furnace is a protective sintering furnace for articles heated in a vacuum environment. There are many heating methods, such as resistance heating, induction heating and microwave heating. Vacuum sintering furnace is generally composed of heating system, vacuum system, measurement and control system, cooling system and furnace body five systems. The heating system is a system that provides heating, heating and heat preservation for the vacuum sintering furnace. It is composed of external power supply, electrode, heater, heating chamber and other heating components and heat preservation components.
The vacuum system is the system which provides the vacuum environment in the furnace and guarantees the vacuum degree in the furnace. The measurement and control system is a system that monitors the temperature and atmosphere in the furnace and gives feedback so that the vacuum sintering furnace can achieve semi-automatic production.
The cooling system provides accelerated cooling for the vacuum sintering furnace, which can greatly improve the efficiency and life of the furnace.
The furnace body is the main body that connects the various systems and houses the heating chamber to provide a vacuum sealing environment. The traditional vacuum sintering furnace has the phenomenon of low efficiency and severe loss. The main reason for this kind of problem is the unreasonable technical method used in the design.
The following will take the resistance heating type vacuum sintering furnace as an example, specific discussion will be made on the technical methods used to improve various system components, to help achieve more efficient and more stable sintering processing.

Improvement Plan
1. Improvement of electrode structure
The electrode is an important part of the heating system. It is the port of the vacuum furnace to connect the heating components in the furnace. The design stage of the electrode device not only requires high sealing, but also increases the working temperature of the workpiece in the vacuum sintering furnace. The existing electrode has reduced the working temperature of the electrode by adding cooling water circulation system in the design stage. However, due to the complicated water circulation, multiple welding connections can easily lead to water leakage. In the high temperature vacuum environment, water leakage will cause serious damage to the workpiece and various systems of the vacuum furnace. So, when the design way to minimize the welding connection, can adopt the way of replacement of electrode material to improve electrode using performance, use high temperature resistant, low resistance, resistivity with temperature change small pieces of material to replace the existing copper electrode and cooling water flowing through the cavity wall only thicker electrodes, and thus greatly reduce the possibility of a leak, and ensure the use of electrode temperature.

In addition, the seal ring used in the electrode device is easy to be aged and damaged when used in a high temperature environment for a long time. It should be replaced at least once every 3 months to achieve a better use effect.

2. Improvement of thermocouple structure
Thermocouple is one of the main ways to measure temperature in vacuum furnace. Because the sealing of the vacuum furnace has certain requirements, and the installation of the thermocouple needs to open holes in the furnace body, so the thermocouple also put forward the requirements of sealing performance, thermocouple sealing performance is directly related to whether the vacuum furnace can meet the requirements. If the vacuum sintering furnace USES the existing industrial thermocouple to measure the temperature, once the protection tube is damaged, it will connect the vacuum furnace to the atmosphere, destroy its sealing, oxidize the workpiece, and even damage the heating device in the furnace. Therefore, in the design stage, detection protection device can be added to ensure the use of thermocouple on the vacuum furnace. Specific implementation can be added between the furnace body and thermocouple atmosphere warehouse, into the atmosphere warehouse into a certain pressure protection gas, and access to the pressure gauge to detect the atmosphere warehouse pressure, through the observation of the pressure gauge reading to visually detect whether the thermocouple is damaged. The advantage of this kind of structure is that it can not only guarantee the working environment of the thermocouple, but also improve the service life of the thermocouple. It is important that even if the protection tube is damaged in the use process, it will not affect the temperature measuring effect of the furnace and the normal production of the workpiece, which greatly improves the safety of the thermocouple used in the vacuum furnace.

At the same time, during the working period, it is necessary to establish a reasonable time interval for maintenance, observe the potential risks and hidden dangers after the operation, and ensure the stability of the vacuum environment.

3. Improvement of water cooling system
Water cooling system is one of the main cooling methods of vacuum sintering furnace. When working, cooling water with sufficient flow must be provided to the above parts; otherwise, heat accumulation will make the working temperature of each part continuously increase, which will make the rubber sealing ring lose sealing effect due to aging and deformation in a very short time, affecting the use of vacuum furnace. At the same time, the users of the vacuum furnace should be informed not to use the cooling water with excessive hardness. When the water with high hardness flows through the cooling parts at high temperature, it will decompose carbonate and attach to the pipe wall, resulting in the effective inner diameter of the cooling pipe reducing or even blocking the cooling pipe, reducing the flow of cooling water.

In order to avoid the vacuum furnace in the operation of the water flow reduction, cut off the situation, in the design should be considered as far as possible. The inlet water system and the drainage system are considered respectively. A total inlet valve is provided for the inlet system, an electric contact pressure gauge is installed on the main inlet pipe to monitor the water pressure, and a water regulation valve is installed on all diverging pipelines. On the other hand, the open water tank is adopted in the drainage system. This structure can reduce the drainage pressure of the diverging pipes, so as to ensure smooth drainage of the branches and visually observe the water flow of the branches. In addition, on larger cooling components, a desilting device can be installed to facilitate the cleaning of scale without affecting the vacuum tightness. In the case of sufficient production capital, the inlet flow switch can also be set in the key components such as water-cooled electrode and heat exchanger to realize the water-off alarm and other interlock control, so as to monitor the working state of the waterway more intuitively and ensure the stability of the system.

Of course, regular use of special chemical cleaning agent to clean the cooling water system is the most effective way to ensure the cooling water pipeline unobstructed.

4. Improvement of furnace door lock tightening structure
The structure of the door lock is the most important part of the sealing furnace body. The original claw-type handwheel locking mode is only through the four points of the furnace door locking, and it is through manual operation, it is easy to make operational mistakes, serious will lead to safety hidden trouble. Now in the design can be used to improve the above problems in the form of locking ring and multi – tooth meshing furnace door. Through the reciprocating action of the cylinder, the locking ring is controlled to reciprocate and rotate in a certain Angle, so that the evenly distributed teeth on the locking ring and the evenly distributed teeth on the furnace door produce staggered and meshing to perform the opening and locking of the furnace door. This multi-linear uniform force distribution greatly improves the sealing performance of the furnace door, adopts pneumatic control to realize semi-automatic operation, and can set the program to prohibit the operation of the furnace door opening before the temperature in the furnace is reduced to a safe temperature, which improves the stability and safety of the vacuum furnace.

With the optimization and improvement of various systems in the vacuum sintering furnace, the equipment performance is more stable and the technical indicators are improved, so as to ensure the product quality, which is of great significance to the improvement and development of vacuum sintering process.

Learn More: Vacuum Sintering Furnace