Vacuum environments have a range of characteristics in metallurgical processes. First of all, the chemical interaction between the substance and the residual gas molecules in the vacuum environment is very weak, so it is very suitable for the smelting and refining of ferrous metals, rare metals, ultra-pure metals and their alloys, and semiconductor materials.
Secondly, in a vacuum environment, the purpose of degassing and refining of molten steel and vacuum carbon deoxidation can be achieved by reducing the partial pressure of a single gas molecule. Another characteristic of the vacuum environment is that it has the ability to carry out certain reactions at lower temperatures, for example, at the same temperature, some reaction processes are difficult to carry out in the atmosphere but very easy at low pressures. This is the basic principle of vacuum compound decomposition and non-ferrous metal refining. In order to monitor the vacuum state of the metallurgical industry, high-precision vacuum sensors are used for in-time measurement and monitoring, which are widely used in the metallurgical industry.
Accurate temperature measurement and control is important in the vacuum metallurgy and heat treatment industry. For example, the accuracy of temperature control has a direct impact on the quality of the carburizing of the workpiece. If there is a fluctuation of ±10°C in the carburizing temperature, it will cause the atmosphere to fluctuate ± carburizing by 0.07%C. The smaller the temperature fluctuation, the smaller the carbon potential fluctuation, so improving the accuracy of temperature measurement and control can reduce the fluctuation of the atmosphere carbon potential and ensure the carburizing quality of the workpiece.
In metallurgical vacuum furnaces, thermocouples are generally used to detect temperature. The characteristics of thermocouple vacuum furnace temperature measurement include:
(1) The thermocouple material should be a material with good thermal conductivity, high surface emissivity and less outgassing under high temperature vacuum; (2) Fast thermocouple thermal response time;
(3) Ensure that the pressure rise rate in the vacuum system meets the requirements of ≤0.4Pa/h:
(4) Strict sealing to ensure that there is no leakage under vacuum, even if the protective tube is broken, it will not affect the vacuum degree of the system;
(5) The interference of alternating electromagnetic field on temperature measurement must be solved for the induction furnace:
(6) The flange connection must comply with GB/T6071-2003 and GB/T6070-1995 ultra-high vacuum, vacuum lower flange standards.
(7) The pipe thread for thermocouple and furnace body should be used as a general sealing pipe thread.