Volgograd State Technical University (Volgograd, Russia):

O. B. Kryuchkov, Cand. Eng., Associate Prof., Deputy Dean, e-mail: bardb@mail.ru
A. V. Krokhalev, Dr. Eng., Associate Prof., Dean, e-mail: kroch@vstu.ru
A. A. Belov, Senior Lecturer, e-mail: aa-belov@bk.ru

Tula State University (Tula, Russia):

P. I. Malenko, Cand. Eng., Associate Prof., e-mail: malenko@tsu.tula.ru

The heating of blooms and cold-charged ingots before metal forming in chamber furnaces, due to the large cross-sections of the billets and their multi-row arrangement in the furnace, contributes to the shielding of the metal and the creation of an uneven temperature field in it, which increases the charge heating time, reduces the furnace productivity and contributes to the at the initial moment of heating the elastic temporary and residual temperature stresses formed in the body of the workpiece after cooling the previous heating. Residual and temporary stresses are added, due to the coincidence of their signs, and can lead to metal buckling and formation of cracks in it. The magnitude of temperature stresses, in addition to the cross-section of the workpiece, is significantly influenced by their location in the furnace. The heating of hot-charged ingots significantly increases the productivity of the furnace units. Knowledge of the temperature field in the heated metal of cold and hot charge, both at the beginning and at the end of heating before metal processing by pressure, is a necessary condition for reducing fuel and electricity consumption, increasing the productivity of the furnace unit and obtaining high-quality deformed metal. In the presented work, a study was made of the influence of the arrangement of blooms in an electric heating well and ingots made of ShKh15 steel in a roller hearth furnace on the time of their heating, the temperature field across the cross section and the furnace productivity. Also, using the literature data on the initial temperature distribution in an ingot made of 02Kh22N5AM3 steel with a mass of 7 t with a liquid core, the temperature field in a hot ingot was calculated after its “undressing”, complete crystallization and further heating for forging. The temperature field in the metal under study and the time of its heating in chamber furnaces were calculated using the Excel tool for solving the differential equation of thermal conductivity in partial derivatives by the finite difference method using an implicit difference scheme under the conditions of the initial uniform and non-uniform temperature distribution over the metal section. The calculations of the heat transfer coefficients by convection and radiation, as well as the thermophysical parameters of the heated metal for the investigated furnaces, billets and their stacking schemes, were carried out using the mathematical package MathConnex (part of MathCadPro).

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