Carburizing furnace for the characteristics of the thermocouple and the common problems existing in the thermocouple _ instrument

For measuring conditions, can't use the temperature measurement of conventional sensors to achieve such as high temperature and strong corrosive medium, under the condition of high temperature melt, vacuum and carburizing, special special sensor must be developed. This article expounds the tungsten-rhenium thermocouples and other special characteristics, performance and application of temperature sensor, emphatically probes into the current temperature field of hot topic: liquid carburizing furnace, liquid aluminum, copper and other high temperature melt continuous temperature measurement; Vacuum brazing furnace, vacuum powder metallurgy sintering furnace, such as temperature measurement and temperature calibration on site. Practice has proved that the newly developed special temperature sensor, not only in line with international standards, to replace imported products, and can also enter the international market. Keywords: temperature sensors, tungsten-rhenium thermocouples, high temperature melt, carburizing furnace, vacuum furnace. Temperature is the international system of units, one of seven basic content and the main parameters in the industrial process control. In the electric heating and heat treatment, furnace lining refractory industry, smelting and refining, accurate temperature measurement, a direct impact on product quality, high and low energy consumption, equipment use lifespan. At present, such as the illustration of the strong reducing atmosphere carburizing furnace, vacuum melting furnace, vacuum brazing, copper, aluminum, magnesium, zinc liquid temperature measurement, are associated with strong corrosion, strong carburizing, high vacuum and high temperature environment parameters, the influence of a variety of industrial temperature measurement is the premise of accurate temperature measurement under special conditions should solve these technologies. 1. Special thermocouple carburizing furnace carburizing process of mechanical manufacturing industry is very important, as the process of reform and opening up, the domestic introduction of many advanced carburizing furnace is used to transform traditional equipment, etc. In this situation, common thermocouple cannot meet the needs of the new cementing equipment. 1, (1) the characteristics of high temperature carburizing furnace, 930 ~ 950 ℃ or higher; (2) reducing atmosphere. 2, the common problems existing in the thermocouple (1) materials using 321 stainless steel under 850 ℃, 930 ℃ in t st13, horizontal installation easy to buckle, life is short; (2) the structure failure to isolate a reducing gas above faults decided to ordinary thermocouple is difficult to meet the strict requirements of carburizing furnace. [2] the development of the new thermocouple in chongqing after the instrument was used to wazhou thermocouple, x ray diffraction analysis results show that the main phase of NiO, Ni, and a small amount of Ni2SiO4, compared to have been used and unused thermocouple, spectral analysis show that after using the thermocouple metal elements decrease relatively, especially the positive of Cr, selective oxidation, the thermocouple thermoelectric emfs negative deviation. 1, material of heat-resisting stainless steel, the use of temperature of 1050 ℃; Type 2, structure the metal and ceramic pipe materialization sealing structure, isolated from the effect of reducing gas, greatly extend the service life of the thermocouple. 2. High temperature melt temperature measurement (1) continuous temperature measuring for liquid aluminum aluminum melting furnace, casting furnace and refining furnace aluminum liquid temperature of molten aluminum in continuous measurement and control, it is important to ensure product quality, saving energy and reducing consumption. Although aluminum liquid temperature is not high, but the strong corrosion, in the process of melting or refining, plus refining agent, degassing agent, coating agent, etc. , for machinery or electromagnetic stirring and grilled slag such as process operations. Therefore, the conventional method is helpless, in view of the above situation, chongqing instrumentation developed two kinds of protection tube. 1) MPT - Type 1 alloy protection tube its features are: high strength, good toughness, corrosion resistance, with the help of mechanical grilled slag, is still not easy to touch. And exported to countries such as France, Italy, Hungary and Mexico. 2) Silicon nitride combined with silicon carbide or surface modification of silicon carbide tube which is characterized by low intensity, easy to damage, but not defiled liquid aluminum, used in aluminum wheel industry very strict with iron impurities. Chongqing instrument adopts silicon nitride combined with silicon carbide or surface modification, replace imported products, the effect is very good also. 2 copper liquid continuous temperature measuring for liquid copper in the copper processing industry continuous temperature measurement, using metal ceramic protection tube, interpolation K type or S type thermocouple, made into materialization thermocouple. Since 20033, proved by field use has the following characteristics: high temperature resistant, long service life, In more than 1000 h) ； Thermocouple stable performance; Safe and reliable.