Addtime： 2020-07-16 Browse times： 3494
Do you know the reason why vacuum furnace can't draw clean air?
1. Water cooling device
Vacuum heat treatment furnace shell, furnace cover, electric heating element conduction disposal (water-cooled electrode), intermediate vacuum heat insulation door and other parts work in vacuum and heating state. In this extremely unfavorable condition, the structure of each component must not be deformed or damaged, and the vacuum sealing ring should not be overheated or burned. Therefore, the water cooling device should be set according to different conditions of each component to ensure that the vacuum heat treatment furnace can operate normally and has enough service life.
2. Adopt low voltage and high current
In the vacuum vessel, when the vacuum space is in the range of several torr-lx10-1 Torr, the conducting conductor in the vacuum vessel will produce glow discharge under high voltage. In the vacuum heat treatment furnace, arc discharge will be produced seriously, which will burn the electric heating elements and heat insulation layer, which will cause serious accidents and losses. Therefore, the working voltage of the electric heating element of the vacuum heat treatment furnace generally does not exceed 80-100 v. At the same time, effective measures should be taken in the structural design of electric heating elements, such as avoiding the parts with tip as far as possible, and the spacing between electrodes should not be too narrow to prevent the occurrence of glow discharge or arc discharge.
3. Most heating and insulation materials can only be used in vacuum
The heating and heat insulation lining materials of vacuum heat treatment furnace work under vacuum and high temperature. Therefore, the requirements for these materials such as high temperature resistance, low steam pressure, good radiation effect and small thermal conductivity are put forward. The requirement of anti oxidation performance is not high. Therefore, tantalum, tungsten, molybdenum and graphite are widely used as heating and heat insulation materials in vacuum heat treatment furnace. These materials are easy to oxidize in the atmosphere, so they can not be used in conventional heat treatment furnaces.
4. Strict vacuum sealing
It is well known that the vacuum heat treatment of metal parts is carried out in a closed vacuum furnace. Therefore, it is of great significance to obtain and maintain the original air leakage rate of the furnace and ensure the working vacuum degree of the vacuum furnace to ensure the quality of the vacuum heat treatment of the parts. Therefore, a key problem of vacuum heat treatment furnace is to have a reliable vacuum sealing structure. In order to ensure the vacuum performance of the vacuum furnace, a basic principle must be followed in the structural design of the vacuum heat treatment furnace, that is, the furnace body should adopt air tight welding, at the same time, the furnace body should be less or no holes should be opened, and the dynamic sealing structure should be less or avoided, so as to reduce the chance of vacuum leakage. The sealing structure must also be designed for the parts and accessories installed on the vacuum furnace body, such as water-cooled electrode and thermocouple export device.
5. High degree of automation
The reason why the automation of vacuum heat treatment furnace is high is that the heating and cooling operations of metal workpieces need more than ten or even dozens of actions to complete. These actions are carried out in the vacuum heat treatment furnace, which is inaccessible to operators. At the same time, some actions such as heating and heat preservation, metal workpiece quenching process requires six actions and should be completed within 15 seconds. In such a rapid condition to complete many actions, it is easy to cause operator tension and constitute misoperation. Therefore, only a higher level of goal-based coordination can be accurate and timely in accordance with the procedures.
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