About design and instrumental control of quality of heating and heat treatment of metal in furnaces

Introduction. In conditions of increasing requirements for the quality of metal heating before rolling or during its heat treatment, the task of creating and improving the algorithmic support of automated process control systems (ACS TP) of heating and thermal furnaces is quite relevant. Aim. The solution to the problem of controlling the temperature drop over the cross section of a metal when it is heated before rolling or during heat treatment is considered. Materials and methods. An analysis of the literature on the problem. A generalization of the results of previous work is carried out both for cases of exposure at a constant temperature of the working space, and at a constant surface temperature of the workpiece, as well as for the case of heating massive bodies of arbitrary shape. Results. It is shown that the solution to the control problem can be reduced either to measuring the current density of the heat flux inside the metal, or to measuring the temperature difference between the furnace and the surface of the slab. The influence on the structure of control algorithms of various features of the real aging process is investigated. The solution of the control problem for the case of massive bodies of arbitrary shape is given. Relations for control are obtained, similar to control algorithms for ingots and slabs. A method for tuning control algorithms to a real process according to current measurements in a regular mode is indicated. It has been established that for the case of symmetric or one-sided heating of slabs in methodological furnaces, it is sufficient to measure the temperature of only one of the surfaces for adjustment, while asymmetric heating requires the measurement of the temperatures of both surfaces. For the case of holding cold-rolled strip rolls in bell-type furnaces, it is necessary to measure the temperature at three radially different points of the base of the lower roll using contact thermocouples. After adjustment, for control in any case, it is enough to measure the temperature at only one point on the surface. The influence of errors in measuring the surface temperature of a metal on the accuracy of control algorithms and on the accuracy of estimating the maximum temperature difference over its cross section is studied. The implementation options for control algorithms in an industrial environment are given. Conclusion. The results of the work can be used in the development and improvement of the algorithmic support of automated process control systems for heating and thermal furnaces.