Vacuum Furnace Characteristics

(1) Strict vacuum sealing: it is known to all 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 of the vacuum furnace to ensure the quality of vacuum heat treatment of parts. So 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 airtight welding, and at the same time, the furnace body should be opened or not as much as possible, and the dynamic sealing structure should be used or avoided as much as possible to reduce the chance of air leakage. The components and accessories installed on the vacuum furnace body, such as water-cooled electrode and thermocouple lead-out device, must also be designed with sealing structure.

(2) Most of the heating and heat insulation materials can only be used in vacuum state: the heating and heat insulation linings of vacuum heat treatment furnace work in vacuum and high temperature, so the requirements of high temperature resistance, low steam pressure, good radiation effect and small thermal conductivity are put forward for these materials. The requirement of oxidation resistance is not high. Therefore, tantalum, tungsten, molybdenum and graphite are widely used as heating and insulation materials in vacuum heat treatment furnace. These materials are very easy to oxidize in the atmospheric state, so they can not be used in conventional heat treatment furnace.

(3) Water cooling device, shell, cover, electric heating element guiding treatment (water-cooling electrode), middle vacuum insulation door and other components of vacuum heat treatment furnace all work under vacuum and heating conditions. In this extremely unfavorable condition, it is necessary to ensure that the structure of each component is not deformed or damaged, and the vacuum sealing ring is not overheated or burnt. Therefore, each component should be equipped with water-cooling device according to different conditions to ensure the normal operation and sufficient service life of the vacuum heat treatment furnace.

(4) Using low voltage and high current: in the vacuum vessel, when the vacuum degree is within the range of several torrs and one lxlo-1 Torr, the electrified conductor in the vacuum vessel will produce glow discharge under high voltage. In the vacuum heat treatment furnace, serious arc discharge will occur, which will burn down the electric heating elements and heat insulation layer, causing major accidents and losses. Therefore, the working voltage of the electric heating elements of the vacuum heat treatment furnace is generally no more than 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 tips as far as possible, and the spacing between electrodes should not be too narrow, so as to prevent the occurrence of glow discharge or arc discharge.

(5) High degree of automation: the reason why the vacuum heat treatment furnace has a high degree of automation is that the heating, cooling and other operations of metal workpieces need dozens or even dozens of actions to complete. These actions are carried out in the vacuum heat treatment furnace and cannot be accessed by the operators. At the same time, some actions, such as heating and heat preservation, require six or six actions to complete the quenching process of metal workpiece within 15 seconds. In such a rapid condition to complete many actions, it is easy to cause the operator’s tension and constitute misoperation. Therefore, only a high level of targeting can coordinate the transfer accurately and timely according to the procedures.