Vacuum heat treatment of metal parts of quenching furnace is carried out in a closed vacuum

Vacuum heat treatment of metal parts of quenching furnace is carried out in a closed vacuum

(1) Strict vacuum seal: It is well known that vacuum heat treatment of metal parts is carried out in a closed vacuum furnace, therefore, obtaining and maintaining the original gas leakage rate of the furnace and ensuring the working vacuum degree of the vacuum furnace are of great significance 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 seal structure. In order to ensure the vacuum performance of the vacuum furnace, a basic principle must be followed in the structure design of the vacuum heat treatment furnace, that is, the furnace body should be air-tight welding, while the furnace body should be less open or not open holes, and the dynamic seal structure should be less used or avoided to minimize the chance of vacuum leakage. The components and accessories installed on the vacuum furnace body, such as water-cooled electrodes and thermocouple export devices, must also be designed to seal the structure.

(2) Most of the quenching furnace heating and insulation materials can only be used in the vacuum state: the heating and insulation lining of the vacuum heat treatment furnace works under 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. Anti-oxidation performance requirements are not high. Therefore, tantalum, tungsten, molybdenum and graphite are widely used as heating and heat insulation materials in vacuum heat treatment furnaces. These materials are easily oxidized in the atmosphere, so these heating and insulation materials cannot be used in conventional heat treatment furnaces.

(3) The water cooling device, the shell, the cover of the vacuum heat treatment furnace, the conduction treatment of the electric heating element (water-cooled electrode), the middle vacuum insulation and other components, all work under vacuum and heat. Working under such extremely unfavorable conditions, it is necessary to ensure that the structure of each component is not deformed, not damaged, and the vacuum seal ring is not overheated and not burned. Therefore, each component should be equipped with a water cooling device according to different conditions to ensure that the vacuum heat treatment furnace can operate normally and have enough service life.

(4) The use of low voltage and high current: in the vacuum container, when the true emptiness is within the range of several to a lxlo-1, the energized conductor in the vacuum container will produce glow discharge at a higher voltage. In the vacuum heat treatment furnace, serious arc discharge will be generated, burning the electric heating element, insulation layer, etc., resulting in major accidents and losses. Therefore, the operating voltage of the electric heating element of the vacuum heat treatment furnace of the quenching furnace is generally not more than 80 to 100 volts. At the same time, effective measures should be taken when designing the structure of the electric heating element, such as avoiding parts with tips as far as possible, and the spacing between the electrodes should not be too narrow to prevent the occurrence of glow discharge or arc discharge.

(5) High degree of automation: The high degree of automation of vacuum heat treatment furnace is because the heating, cooling and other operations of metal workpieces require a dozen or even dozens of actions to complete. These actions are carried out inside the vacuum heat treatment furnace and cannot be approached by the operator. At the same time, some actions such as heating and insulation after the end of the metal workpiece quenching process must be six or six actions and to be completed within 15 seconds. In such a rapid condition to complete many actions, it is easy to cause the operator tension and constitute misoperation. Therefore, only the higher visualization can accurately and timely coordinate the movement according to the procedure.