Temperature detection and control of heat treatment furnace
The temperature detection system of heat treatment furnace is mainly composed of P LC(PLC) and sensor. Temperature detection system implementation process is mainly the sensor converts the temperature signal, the signal through P L C input module into P L, C P LC CPU CP (U) in through A/D conversion will send electrical signals into P L C identifiable value, then the PLC (S P) through the system set temperature and real temperature differences (P V) by P I D operation for automatic control, temperature test data can be recorded by history curve as the basis of heating furnace products qualified.
The selection of testing equipment: we used for heating furnace of steel tube heat treatment furnace heating generally adopts thermocouple test chamber of a stove or furnace temperature, real-time monitoring of furnace heating effect, according to the temperature of the metal heating needs to control furnace temperature curve; The temperature of the measured object is measured by the infrared temperature measuring instrument outside the heating furnace, which reflects the heating degree of the metal in the heating furnace and the abnormal situation in the heating process in time. Electric potential difference produced by the thermocouple signal and the analog signals produced by the infrared thermometer can be P L C collection, these signals through P LC after processing as a control signal to control furnace temperature, record and save.
(1) temperature measuring equipment is mainly used in furnace measurement.
At present, the thermocouple temperature measurement method is widely used in the internal and external temperature measurement. Thermocouple temperature measurement principle: two different ingredients of conductor on both ends of the synthesis loop, when the junction temperature is not at the same time, in the circuit will generate electromotive force, this kind of phenomenon called the thermoelectric effect, and this kind of electromotive force is called thermoelectric potential. The thermocouple used in heating furnace is mainly K degree and S degree thermocouple. K even, the material of nickel chromium -- nickel silicon, long time temperature range 0 ~ 9 00, general metal material price is low; S I, material platinum rhodium 1 0 -- platinum, long time temperature range 0 ~ 1 3 0 0, precious metal material high price. Based on the temperature range, accuracy grade and cost performance of the thermocouple, it is recommended that the quenching furnace in the heat treatment process should adopt the class S couple, and the measurement error is 2.25 ~ 2.75. The measurement error is 2. 4 ~ 3. 2.
(2) temperature measuring equipment is mainly used for external measurement of furnace.
Principle of infrared measuring temperature: the temperature in the objects of a degree above absolute zero radiation infrared, through the infrared detector converts objects radiation power signal to electrical signals, then convert temperature signal, realize remote temperature measurement on the target object. As shown in figure 1, in the same wavelength range energy emitted by an object the higher the temperature is, the greater the infrared temperature measurement device is using this far away from the detected radiation energy and then calculated the size of the actual temperature of the object.
There are many factors influencing the measurement accuracy, including the measurement accuracy grade, distance and wavelength of the measuring equipment. Of objects of different temperature of the radiant energy distribution in different wavelength range is not the same, the higher the temperature of radiation energy areas of high bias wavelength is more shortcomings, so low temperature object should choose a longer wavelength temperature measuring equipment, and measurement of the high temperature object should choose shorter wavelength of the equipment.