Simulation of the Heating of Oxidizing Metal

Аннотация

Abstract—A method is developed for simulation of the heating of oxidizing metal billet when the billet dimensions and the thickness of the scale layer vary over time. The approach adopted simplifies the use of software to analyze objects with varying geometry and, in consequence, may greatly facilitate the development of mathematical models for metallurgical processes. The oxidation of metal is modeled here on the basis of the equivalent thermal conductivity. This method is verified experimentally, and its applicability in improving the monitoring of industrial heating processes is demonstrated. The method was refined in experiments at stepping-hearth furnace 3 in the 150 mill at Nizhne-Serginsk metalware and metallurgical plant. The thickness of the scale layer, which varies over time, is calculated, and presented in graphical form. ANSYS Multiphysics software is employed to solve the corresponding nonsteady heat-conduction problem with boundary conditions of the first kind. In modeling, a finite-element grid is constructed. This grid is sufficiently detailed to ensure reliable results but may be used on low-power computers. Various simplifications are made: in particular, the computational algorithm assumes that the thickness of the scale layer is uniquely determined by the billet’s surface temperature. The temperature distribution over the billet thickness is determined. To compare the temperature in the metal and the scale layer, graphs and isotherms are plotted. The calculated temperature difference in the scale layer for the chosen furnace conditions is compared with the actual experimental data. A nonsteady problem with changing boundaries is solved here. The object considered is a metal billet (a real body) with scale layer that increases over time. In solving the problem, this real body is replaced by an equivalent (hypothetical) body with constant mean dimensions. Assuming similarity of the thermophysical processes, properties of the equivalent body that vary in accordance with the dimensions of the real body are determined.