Because the heating and cooling operations of metal workpieces require more than a dozen or even dozens of actions to complete. These actions are carried out in the vacuum heat treatment furnace and cannot be approached by the operator, so the degree of automation of the vacuum heat treatment furnace is required. At the same time, some actions, such as after the end of heating and insulation, the quenching process of the metal workpiece must be six or seven actions and must be completed within 15 seconds. Such agile conditions to complete many actions, it is easy to cause the operator to be nervous and constitute a misoperation. Therefore, only a high degree of automation can be coordinated accurately and in a timely manner according to the procedure.
Vacuum heat treatment of metal parts is carried out in a closed vacuum furnace, and strict vacuum sealing is well known. Therefore, obtaining and insisting on the original air leakage rate of the furnace and ensuring the working vacuum degree of the vacuum furnace is of great significance to ensure the quality of vacuum heat treatment of parts. Therefore, a key issue for vacuum heat treatment furnaces 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 airtightly welded, and at the same time, the furnace body should be as little or no hole as possible, and the dynamic sealing structure should be used less or avoid the use of dynamic sealing structure, so as to minimize the opportunity of vacuum leakage. The components and accessories installed on the vacuum furnace body, such as water-cooled electrodes and thermocouple outlets, must also be designed with a hermetically sealed structure.
Most heating and insulation materials can only be used in vacuum. The heating and thermal insulation lining of the vacuum heat treatment furnace works under vacuum and high temperature, so these materials are required to withstand high temperature, good radiation results and small thermal conductivity. The antioxidant performance is not required. Therefore, tantalum, tungsten, molybdenum and graphite are widely used as heating and insulating materials in vacuum heat treatment furnaces. These materials are highly susceptible to oxidation in the atmosphere, so they cannot be used in ordinary heat treatment furnaces.