Volgograd State Technical University, Volgograd, Russia:

O. B. Kryuchkov, Cand. Eng., Associate Professor, Deputy Dean, e-mail: bardb@mail.ru
A. V. Krokhalev, Dr. Eng., Associate Professor, Dean, e-mail: kroch@vstu.ru
E. V. Sedov, Cand. Eng., Associate Professor, Dept. of Materials Technology, e-mail: ehse@yandex.ru

Tula State University, Tula, Russia:

P. I. Malenko, Cand. Eng., Associate Professor, Dept. of Welding, Casting and Technology of Structural Materials, e-mail: malenko@tsu.tula.ru

Heating of layered metal cages in bell furnaces, for example, stops from strip coils, due to the presence of gas gaps between the layers in them, leads to an increase in the temperature drop in the radial direction with a simultaneous temperature drop along the height of the charge. An accurate calculation of the heating time of the charges of strip coils requires knowledge of the temperature field in them, and, consequently, the radial equivalent coefficient of thermal conductivity and the end coefficient of thermal conductivity, on which the consumption of electricity, fuel and the performance of the furnace will depend. The formula and method for calculating the equivalent coefficient of thermal conductivity in the radial and end directions of ta strip coil are proposed, based on the numerical solution of the differential equation of thermal conductivity using an explicit difference scheme, a constant coefficient of thermal conductivity and boundary conditions of the first kind, suggesting the useof its experimental values as the tem perature of the roll surface at various points in time. The values of the thermal conductivity coefficients calculated according to the proposed formula and methodology were confirmed by experimental laboratory heating of a 0,3 mm thick steel strip coil made of electrical steel E3412; height, inner and outer diameters of the coil, respectively: 52,0; 51,882; 79,667 mm; with the number of tape layers per side equal to 46; with a filling coefficient of 0,86 and the degree of contact of layers – 2,9%. The strip coil was heated both together with the furnace to a temperature of 920 °C, and when it was loaded into a preheated furnace to a temperature of 620 °C, followed by heating to 920 °C and holding. When forming the charges, two heating options were carried out: radial and end heating.

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