tempering furnace automatic control system
The heat treatment process is very strict to the temperature control precision and the uniformity of furnace temperature. The key to ensure the accuracy of heating furnace is to design and select the temperature control system of heating furnace. According to heat loss and heat transfer mode of well type tempering furnace temperature control system is designed, following the requirements of heat treatment process parameters and original temperature measurement, temperature measuring instrument table, temperature detecting and recording system to carry on the design, and analyze the temperature control system of the integrated error and detection of furnace temperature uniformity has reached the reasonable temperature control effect.
Furnace temperature control system
1. Selection of temperature control mode
According to the principle and structure of the well furnace, three single-phase power supply is used to adjust the power of each section through the thyristor and three solid state relays respectively. XMA5000 series intelligent expert self-tuning time program PID controller realizes the PID adjustment by time scale, strong trigger mode, and adjust the control temperature through the zero trigger of the bidirectional thyristor. Time application because XMA5000 series intelligent expert self-tuning PID regulator has a P, I, D parameters self-tuning function and the function of overshoot, for different control object has a strong applicability, easy debugging and can get the best control effect, implementation work condition 3 three sections of uniform temperature in the furnace, the furnace temperature control central point for furnace duplex two-point temperature control.
2. Selection of temperature measuring element and thermometer
According to the temperature range of pit type furnace and temperature variation, selection of nickel chrome - nickel silicon (K type thermocouple, it has the thermoelectric potential high efficiency, high sensitivity, good stability and good uniformity, etc. The depth of the thermocouple should not be less than the protective diameter (8--10 times), reducing the measurement error. The response time of temperature measurement can be reduced by reducing the thickness and diameter of the thermocouple protection tube. If the measured temperature is 900 degrees, the temperature measurement accuracy is plus or minus 0.5 percent, and the absolute error is allowed to be plus or minus 4.5. Then, a 0--1000 is selected, and the error is allowed to be plus or minus 0.4%, that is, the temperature measuring thermocouple with a degree of accuracy of 1.
The accuracy of temperature measurement is not only related to the accuracy grade of the selected thermometer, but also to the range of measuring instrument. When selecting the instrument range, the instrument with the same accuracy level should choose the instrument with the same measurement limit as the measured temperature.
Furnace temperature monitoring and recording system
Pit type furnace of the furnace temperature monitoring and process data recorded by the heat treatment automatic collecting and distributing control system software to complete, through the control cabinet of the touch screen system or computer system to operation and observation. The operation of the whole system is visualized in the general view of the system. Display temperature collection value, given value, power output percentage, current, voltage, communication status, alarm status, control mode, operation mode, etc. The software includes real-time curve, historical curve, historical data, process record, alarm recording, process curve programming and other data record storage mode and operation processing method. According to the heat treatment process, the user can edit the required process curve flexibly, and draw the process curve.
In order to adapt to the operation requirements of different levels of users, multiple user login rights are designed, which can effectively prevent misoperation of professional data by front-line operators.