(1) 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 leakage rate of the furnace and ensure the working vacuum degree of the vacuum furnace to ensure the quality of vacuum heat treatment of 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 be air tight welded, at the same time, the furnace body should be opened or not opened as much as possible, and the dynamic sealing structure should be used or avoided, so as to minimize the chance of vacuum leakage. The components and accessories installed on the vacuum furnace body, such as water-cooled electrode and thermocouple export device, must also be designed with sealing structure.

(2) Most of the heating and heat insulation materials of quenching furnace can only be used in vacuum state: the heating and heat insulation lining materials 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 easy to oxidize in the atmosphere, so the conventional heat treatment furnace can not use these heating and insulation materials.

(3) The water cooling device, the shell and cover of the vacuum heat treatment furnace, the conductive disposal of the electric heating elements (water-cooling electrode), the middle vacuum insulation door and other parts all work in the vacuum and heating state. In this extremely unfavorable condition, we must ensure that the structure of each part is not deformed or damaged, and the vacuum sealing ring is not overheated or burned. Therefore, water cooling devices should be set up according to different conditions to ensure that the vacuum heat treatment furnace can operate normally and have enough service life.

(4) Using low voltage and high current: in the vacuum vessel, when the vacuum void is in the range of several torr to 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 be produced, and the electric heating elements and insulation layer will be burned, resulting in major accidents and losses. Therefore, the working voltage of the electric heating element of the quenching furnace vacuum heat treatment furnace is generally less 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 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.

(5) High degree of automation: the reason for the high degree of automation of vacuum heat treatment furnace is that the heating, cooling and other operations of metal workpiece 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 the operators. Some metal parts should be heated within 15 seconds. In such a rapid condition to complete many actions, it is easy to cause the operator's tension and constitute a misoperation. Therefore, only a high degree of targeting can coordinate the mobilization accurately and timely according to the procedures.